http://bacnetwiki.com/api.php?action=feedcontributions&feedformat=atom&user=BACnetEdBACnet Wiki - User contributions [en]2026-11-07T06:32:46ZUser contributionsMediaWiki 1.40.0http://bacnetwiki.com/index.php?title=MS/TP_Wiring_Guide&diff=13757MS/TP Wiring Guide2026-10-04T15:39:30Z<p>BACnetEd: </p>
<hr />
<div>'''Wiring Guide for BACnet MS/TP<br />
'''<br />
<br />
{| class="wikitable sortable"<br />
! Manufacturer !! Part Number !! Voltage Rating !! Gauge AWG !! Pairs !! Temp Rating °C !! Impedance ohms !! Capacitance pF/ft. !! Cable Dia.<br />
|-<br />
| Alpha Wire || 6453 || 300V PLTC, CM || 22 || 1 || –20/+60 || 120 || 20 || 0.28″<br />
|-<br />
| Alpha Wire || 6454 || 300V PLTC, CM || 22 || 1.5 || –20/+60 || 120 || 11 || 0.32″<br />
|-<br />
| Automation Direct || L19827 || 300V CM/CL2 || 24 || 1 || +60 || 120 || 13 || 0.24<br />
|-<br />
| Belden || 3074F || 600V PLTC, TC || 18 || 1 || –40/+75 || 124 || 12 || 0.46<br />
|-<br />
| Belden || 3105A || 300V PLTC/CM || 22 || 1 || –20/+60 || 120 || 11 || 0.28<br />
|-<br />
| Belden || 3106A || 300V PLTC/CM || 22 || 1.5 || –20/+60 || 120 || 11 || 0.30<br />
|-<br />
| Belden || 3107A || 300V PLTC/CM || 22 || 1 || –20/+60 || 120 || 36 || 0.35<br />
|-<br />
| Belden || 9841 || 300V CM, UL2919 || 24 || 1 || –30/+80 || 120 || 13 || 0.23<br />
|-<br />
| Belden || 82841 || 300V Plenum || 24 || 1 || 0/+75 || 120 || 12 || 0.23<br />
|-<br />
| Belden || 89841 || 300V Plenum || 24 || 1 || –70/+150 || 120 || 13 || 0.23<br />
|-<br />
| Carol || C2514 || 300V CM, CMH || 22 || 1 || –20/+75 || — || 20 || 0.17<br />
|-<br />
| Carol || C2536A || 600V UL2106 || 16 || 1 || –20/+75 || — || 20 || 0.17<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=MS/TP_Wiring_Guide&diff=13756MS/TP Wiring Guide2026-10-04T15:38:45Z<p>BACnetEd: </p>
<hr />
<div>'''Wiring Guide for BACnet MS/TP<br />
'''<br />
<br />
{| class="wikitable sortable"<br />
! Manufacturer !! Part Number !! Voltage Rating !! Gauge AWG !! Pairs !! Temp Rating °C !! Impedance ohms !! Capacitance pF/ft. !! Cable Dia.<br />
|-<br />
| Alpha Wire || 5430/2 || 600V AWM/UL1015 || 18 || 1 || –30/+105 || 58 || 39 || 0.28″<br />
|-<br />
| Alpha Wire || 6453 || 300V PLTC, CM || 22 || 1 || –20/+60 || 120 || 20 || 0.28″<br />
|-<br />
| Alpha Wire || 6454 || 300V PLTC, CM || 22 || 1.5 || –20/+60 || 120 || 11 || 0.32″<br />
|-<br />
| Automation Direct || L19827 || 300V CM/CL2 || 24 || 1 || +60 || 120 || 13 || 0.24<br />
|-<br />
| Belden || 3074F || 600V PLTC, TC || 18 || 1 || –40/+75 || 124 || 12 || 0.46<br />
|-<br />
| Belden || 3105A || 300V PLTC/CM || 22 || 1 || –20/+60 || 120 || 11 || 0.28<br />
|-<br />
| Belden || 3106A || 300V PLTC/CM || 22 || 1.5 || –20/+60 || 120 || 11 || 0.30<br />
|-<br />
| Belden || 3107A || 300V PLTC/CM || 22 || 1 || –20/+60 || 120 || 36 || 0.35<br />
|-<br />
| Belden || 8761 || 300V AWM UL2092 || 22 || 1 || –20/+60 || 64 || 24 || 0.18<br />
|-<br />
| Belden || 9841 || 300V CM, UL2919 || 24 || 1 || –30/+80 || 120 || 13 || 0.23<br />
|-<br />
| Belden || 82841 || 300V Plenum || 24 || 1 || 0/+75 || 120 || 12 || 0.23<br />
|-<br />
| Belden || 89841 || 300V Plenum || 24 || 1 || –70/+150 || 120 || 13 || 0.23<br />
|-<br />
| Carol || C2514 || 300V CM, CMH || 22 || 1 || –20/+75 || — || 20 || 0.17<br />
|-<br />
| Carol || C2536A || 600V UL2106 || 16 || 1 || –20/+75 || — || 20 || 0.17<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=MS/TP_Wiring_Guide&diff=13755MS/TP Wiring Guide2026-10-04T15:37:58Z<p>BACnetEd: Created page with "``` Wiring Guide for BACnet MS/TP {| class="wikitable sortable" ! Manufacturer !! Part Number !! Voltage Rating !! Gauge AWG !! Pairs !! Temp Rating °C !! Impedance ohms !! Capacitance pF/ft. !! Cable Dia. |- | Alpha Wire || 5430/2 || 600V AWM/UL1015 || 18 || 1 || –30/+105 || 58 || 39 || 0.28″ |- | Alpha Wire || 6453 || 300V PLTC, CM || 22 || 1 || –20/+60 || 1..."</p>
<hr />
<div>``` Wiring Guide for BACnet MS/TP<br />
{| class="wikitable sortable"<br />
! Manufacturer !! Part Number !! Voltage Rating !! Gauge AWG !! Pairs !! Temp Rating °C !! Impedance ohms !! Capacitance pF/ft. !! Cable Dia.<br />
|-<br />
| Alpha Wire || 5430/2 || 600V AWM/UL1015 || 18 || 1 || –30/+105 || 58 || 39 || 0.28″<br />
|-<br />
| Alpha Wire || 6453 || 300V PLTC, CM || 22 || 1 || –20/+60 || 120 || 20 || 0.28″<br />
|-<br />
| Alpha Wire || 6454 || 300V PLTC, CM || 22 || 1.5 || –20/+60 || 120 || 11 || 0.32″<br />
|-<br />
| Automation Direct || L19827 || 300V CM/CL2 || 24 || 1 || +60 || 120 || 13 || 0.24<br />
|-<br />
| Belden || 3074F || 600V PLTC, TC || 18 || 1 || –40/+75 || 124 || 12 || 0.46<br />
|-<br />
| Belden || 3105A || 300V PLTC/CM || 22 || 1 || –20/+60 || 120 || 11 || 0.28<br />
|-<br />
| Belden || 3106A || 300V PLTC/CM || 22 || 1.5 || –20/+60 || 120 || 11 || 0.30<br />
|-<br />
| Belden || 3107A || 300V PLTC/CM || 22 || 1 || –20/+60 || 120 || 36 || 0.35<br />
|-<br />
| Belden || 8761 || 300V AWM UL2092 || 22 || 1 || –20/+60 || 64 || 24 || 0.18<br />
|-<br />
| Belden || 9841 || 300V CM, UL2919 || 24 || 1 || –30/+80 || 120 || 13 || 0.23<br />
|-<br />
| Belden || 82841 || 300V Plenum || 24 || 1 || 0/+75 || 120 || 12 || 0.23<br />
|-<br />
| Belden || 89841 || 300V Plenum || 24 || 1 || –70/+150 || 120 || 13 || 0.23<br />
|-<br />
| Carol || C2514 || 300V CM, CMH || 22 || 1 || –20/+75 || — || 20 || 0.17<br />
|-<br />
| Carol || C2536A || 600V UL2106 || 16 || 1 || –20/+75 || — || 20 || 0.17<br />
|}<br />
```<br />
<br />
MediaWiki ignores the extra spaces, so they are purely to make the source easier to read and edit.</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BACnet_MS/TP_Best_Practices&diff=13754BACnet MS/TP Best Practices2026-10-04T15:37:01Z<p>BACnetEd: /* Resources */</p>
<hr />
<div>BACnet MS/TP gets a bad rap in the field. Some installers do a great job and have networks that run with zero errors for years. Other networks suffer continuous (and largely invisible) communication errors. This page will accumulate a list of best practices for designers, installers and users.<br />
<br />
=== Two-wire vs Three-wire ===<br />
<br />
Firstly consider the following scenario. <br />
<br />
If there is only one pair pf wires (A and B signals), and if a device is floating (i.e. not connected to a ground anywhere, think battery powered or transformer isolated), then due to the various designed in or parasitic resistances, the circuit common (or 0v) will naturally be a few volts below the A/B potential. The RS-485 transceiver will then be able to extract the data signal quite happily. <br />
<br />
==== Two-Wire ====<br />
With this arrangement, the circuitry 0v is normally grounded to the building ground by manufacturer's specifications and common practices. There is nothing wrong with this approach if all the grounds of all the devices are within +/- 7 volts of each other. <br />
<br />
The problem comes when there are large ground differences between nodes. This happens all the time when different building supply phases are used for different BACnet nodes, or if there are large loads scattered around the building, which cause large currents, thus voltage drops in the various supplies.<br />
<br />
<br />
==== Three-Wire (or Isolated RS-485) ====<br />
The third, or common wire carries the 'reference signal' from node to node. Per the scenario above it is not needed for operation, since the isolated circuit will arrange itself around the A/B voltages. However, the common return is important to remove the common-mode noise on the wire, thus removing the for emitted noise from the network. <br />
<br />
It should never be grounded at more than one point, since this is a) unnecessary, b) introduced ground-loop noise into the circuit.<br />
<br />
<br />
==== A-/B+ or Polarity Issues ====<br />
Signal Polarity, in particular is fraught with contradictions and errors. We have tried to summarize the situation in the [[RS-485 Polarity]] page.<br />
<br />
<br />
=== Resources ===<br />
* A very good MS/TP article from [https://cgproducts.johnsoncontrols.com/met_pdf/12011034.pdf JCI]<br />
* Interesting load analysis (with hockey stick under high loads) ([https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=860960 link])<br />
* Application Guide from [https://sid.siemens.com/r/A6V11623436 Siemens]<br />
* Table of RS-485 cable part numbers [https://ctlsys.com/support/rs-485_cables_for_bacnet_and_modbus/ Continental Control Systems]<br />
* [[MS/TP Wiring Guide]]</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity_First_Principles&diff=13753RS-485 Polarity First Principles2026-10-04T15:15:33Z<p>BACnetEd: Created page with "'''Attempting to reduce RS-485 polarity issues to fundamental reasoning * A>B means "binary 0 on the bus" or "ON" - from the standard * "MARK" state (no transmitters enabled) is defined by line biasing, and sets A>B, and this is "Idle" * UARTs output a logic '1' (high voltage) for Idle state! * A is non-inverting (+), B is inverting (-) Done"</p>
<hr />
<div>'''Attempting to reduce RS-485 polarity issues to fundamental reasoning<br />
<br />
* A>B means "binary 0 on the bus" or "ON" - from the standard<br />
* "MARK" state (no transmitters enabled) is defined by line biasing, and sets A>B, and this is "Idle"<br />
* UARTs output a logic '1' (high voltage) for Idle state!<br />
* A is non-inverting (+), B is inverting (-)<br />
<br />
<br />
Done</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13752RS-485 Polarity2026-10-04T15:08:55Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
Here is a minimal set of statements that provide the backbone to this article [[RS-485 Polarity First Principles]]<br />
<br />
'''Quotations directly from the Standard. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Common !! Shield !! - !! Isolated !! Manufacturer !! Model !! Comment !! Source<br />
|-<br />
| + || - || || || || || BACnet Specification || || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| A+ || B- || || || || || AirBox || || <br />
|-<br />
| A+ || A- || S || None || || Isolated || || JACE 8000 || RS485-A / Com 1 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| B+ || B- || S || None || || Isolated || || JACE 8000 || RS485-B / Com 2 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| A || B || || || || || BITS || || <br />
|-<br />
| RT+ || RT- || || || || || EnOcean || SmartServer IoT || <br />
|-<br />
| + || - || || || || || FT-Click || <br />
|-<br />
| + || - || SC || SH || || || CControls || BASRouter LX|| + 1 SC COM SH - see docs<br />
|-<br />
| + || - || || || || || Onicon || F-4300 || <br />
|-<br />
| B+ || A- || SGND || Shld || || || MBS || UBR-01 Mk II || This is contrary to everyone else <br />
|-<br />
| Tx/+ || Rx/- || GND || - || || Isolated || MSA || FieldServer FPC-N35 || [https://us.msasafety.com/p/protonode?section=literature link]<br />
|-<br />
| U+ || U- || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || || || || || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485]<br />
|-<br />
| A || B || || || || || || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || || || || KMC || router || A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13751RS-485 Polarity2026-10-02T11:25:02Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Common !! Shield !! - !! Isolated !! Manufacturer !! Model !! Comment !! Source<br />
|-<br />
| + || - || || || || || BACnet Specification || || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| A+ || B- || || || || || AirBox || || <br />
|-<br />
| A+ || A- || S || None || || Isolated || || JACE 8000 || RS485-A / Com 1 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| B+ || B- || S || None || || Isolated || || JACE 8000 || RS485-B / Com 2 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| A || B || || || || || BITS || || <br />
|-<br />
| RT+ || RT- || || || || || EnOcean || SmartServer IoT || <br />
|-<br />
| + || - || || || || || FT-Click || <br />
|-<br />
| + || - || SC || SH || || || CControls || BASRouter LX|| + 1 SC COM SH - see docs<br />
|-<br />
| + || - || || || || || Onicon || F-4300 || <br />
|-<br />
| B+ || A- || SGND || Shld || || || MBS || UBR-01 Mk II || This is contrary to everyone else <br />
|-<br />
| Tx/+ || Rx/- || GND || - || || Isolated || MSA || FieldServer FPC-N35 || [https://us.msasafety.com/p/protonode?section=literature link]<br />
|-<br />
| U+ || U- || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || || || || || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485]<br />
|-<br />
| A || B || || || || || || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || || || || KMC || router || A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13750RS-485 Polarity2026-10-02T11:22:20Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Common !! Shield !! - !! Isolated !! Manufacturer !! Model !! Comment !! Source<br />
|-<br />
| + || - || || || || || BACnet Specification || || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| A+ || B- || || || || || AirBox || || <br />
|-<br />
| A+ || A- || S || None || || Isolated || || JACE 8000 || RS485-A / Com 1 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| B+ || B- || S || None || || Isolated || || JACE 8000 || RS485-B / Com 2 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| A || B || || || || || BITS || || <br />
|-<br />
| RT+ || RT- || || || || || EnOcean || SmartServer IoT || <br />
|-<br />
| + || - || || || || || FT-Click || <br />
|-<br />
| + || - || SC || SH || || || CControls || BASRouter LX|| + 1 SC COM SH - see docs<br />
|-<br />
| + || - || || || || || Onicon || F-4300 || <br />
|-<br />
| B+ || A- || SGND || Shld || || || MBS || UBR-01 Mk II || This is contrary to everyone else <br />
|-<br />
| Tx/+ || Rx/- || GND || - || || Isolated || MSA || FieldServer FPC-N35 || [file:///C:/Users/Ed/Downloads/DS_ProtoNode_FPC-N3X_&_N34X.pdf link]<br />
|-<br />
| U+ || U- || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || || || || || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485]<br />
|-<br />
| A || B || || || || || || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || || || || KMC || router || A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13749RS-485 Polarity2026-10-02T11:21:11Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Common !! Shield !! - !! Isolated !! Manufacturer !! Model !! Comment <br />
|-<br />
| + || - || || || || || BACnet Specification || || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| A+ || B- || || || || || AirBox || || <br />
|-<br />
| A+ || A- || S || None || || Isolated || || JACE 8000 || RS485-A / Com 1 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| B+ || B- || S || None || || Isolated || || JACE 8000 || RS485-B / Com 2 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| A || B || || || || || BITS || || <br />
|-<br />
| RT+ || RT- || || || || || EnOcean || SmartServer IoT || <br />
|-<br />
| + || - || || || || || FT-Click || <br />
|-<br />
| + || - || SC || SH || || || CControls || BASRouter LX|| + 1 SC COM SH - see docs<br />
|-<br />
| + || - || || || || || Onicon || F-4300 || <br />
|-<br />
| B+ || A- || SGND || Shld || || || MBS || UBR-01 Mk II || This is contrary to everyone else <br />
|-<br />
| Tx/+ || Rx/- || GND || - || || Isolated || MSA || FieldServer FPC-N35 || <br />
|-<br />
| U+ || U- || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || || || || || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485]<br />
|-<br />
| A || B || || || || || || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || || || || KMC || router || A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13748RS-485 Polarity2026-09-30T10:43:28Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Common !! Shield !! - !! Isolated !! Manufacturer !! Model !! Comment <br />
|-<br />
| + || - || || || || || BACnet Specification || || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| A+ || B- || || || || || AirBox || || <br />
|-<br />
| A+ || A- || S || None || || Isolated || || JACE 8000 || RS485-A / Com 1 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| B+ || B- || S || None || || Isolated || || JACE 8000 || RS485-B / Com 2 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| A || B || || || || || BITS || || <br />
|-<br />
| RT+ || RT- || || || || || EnOcean || SmartServer IoT || <br />
|-<br />
| + || - || || || || || FT-Click || <br />
|-<br />
| + || - || SC || SH || || || CControls || BASRouter LX|| + 1 SC COM SH - see docs<br />
|-<br />
| + || - || || || || || Onicon || F-4300 || <br />
|-<br />
| B+ || A- || SGND || Shld|| || || MBS || UBR-01 Mk II || This is obviously contrary to everyone else <br />
|-<br />
| 485+ || 485- || || || || Isolated || MSA || FieldServer FPC-N35 || <br />
|-<br />
| U+ || U- || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || || || || || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || || || || || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485]<br />
|-<br />
| A || B || || || || || || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || || || || KMC || router || A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13747RS-485 Polarity2026-09-30T10:34:01Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Common !! Shield !! Class !! Isolated !! Manufacturer !! Comment !!<br />
|-<br />
| A || B || || || Nominal || || BITS<br />
|-<br />
| A+ || A- || S || None || Nominal || Isolated || JACE 8000 || RS485-A / Com 1 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| B+ || B- || S || None || Nominal || Isolated || JACE 8000 || RS485-B / Com 2 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| A || B || || || Nominal || || BITS<br />
|-<br />
| + || - || || || Symbol || || BACnet Specification || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| RT+ || RT- || || || || || EnOcean SmartServer IoT || <br />
|-<br />
| + || - || || || Symbol || || FT-Click || <br />
|-<br />
| + || - || SC || SH || Symbol || || BASRouter LX|| + 1 SC COM SH - see docs<br />
|-<br />
| + || - || || || Symbol || || Onicon F-4300 || <br />
|-<br />
| B+ || A- || || || || || MBS UBR-01 Mk II || This is obviously contrary to everyone else <br />
|-<br />
| 485+ || 485- || || || Symbol || Isolated || FieldServer FPC-N35 || <br />
|-<br />
| U+ || U- || || || || || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || || || || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || || || || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485], AirBox<br />
|-<br />
| A || B || || || || || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || || || || KMC router, A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13746RS-485 Polarity2026-09-30T10:29:55Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Common !! Shield !! Class !! Isolated !! Manufacturer !! Comment !!<br />
|-<br />
| A || B || || || Nominal || || BITS<br />
|-<br />
| A+ || A- || S || || Nominal || || JACE 8000 || RS485-A / Com 1 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| B+ || B- || S || || Nominal || || JACE 8000 || RS485-B / Com 2 - Tridium mixes 'A' and 'B' intent<br />
|-<br />
| A || B || || || Nominal || || BITS<br />
|-<br />
| + || - || || || Symbol || || BACnet Specification || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| RT+ || RT- || || || || || EnOcean SmartServer IoT || <br />
|-<br />
| + || - || || || Symbol || || FT-Click || <br />
|-<br />
| + || - || || || Symbol || || BASRouter LX|| <br />
|-<br />
| + || - || || || Symbol || || Onicon F-4300 || <br />
|-<br />
| B+ || A- || || || || || MBS UBR-01 Mk II || This is obviously contrary to everyone else <br />
|-<br />
| 485+ || 485- || || || Symbol || || FieldServer FPC-N35 || <br />
|-<br />
| U+ || U- || || || || || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || || || || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || || || || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485], AirBox<br />
|-<br />
| A || B || || || || || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || || || || KMC router, A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13745RS-485 Polarity2026-09-30T10:28:12Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Common !! Shield !! Class !! Isolated !! Manufacturer !! Comment !!<br />
|-<br />
| A || B || || || Nominal || || BITS<br />
|-<br />
| A+ || A- || S || || Nominal || || JACE 8000<br />
|-<br />
| A || B || || || Nominal || || BITS<br />
|-<br />
| + || - || || || Symbol || || BACnet Specification || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| RT+ || RT- || || || || || EnOcean SmartServer IoT || <br />
|-<br />
| + || - || || || Symbol || || FT-Click || <br />
|-<br />
| + || - || || || Symbol || || BASRouter LX|| <br />
|-<br />
| + || - || || || Symbol || || Onicon F-4300 || <br />
|-<br />
| B+ || A- || || || || || MBS UBR-01 Mk II || This is obviously contrary to everyone else <br />
|-<br />
| 485+ || 485- || || || Symbol || || FieldServer FPC-N35 || <br />
|-<br />
| U+ || U- || || || || || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || || || || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || || || || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485], AirBox<br />
|-<br />
| A || B || || || || || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || || || || KMC router, A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13744RS-485 Polarity2026-09-30T10:19:58Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Common !! Shield !! Class !! Isolated !! Manufacturer !! Comment !!<br />
|-<br />
| A || B || || || Nominal || || BITS, FieldServer<br />
|-<br />
| + || - || || || Symbol || || BACnet Specification || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| RT+ || RT- || || || || || EnOcean SmartServer IoT || <br />
|-<br />
| + || - || || || Symbol || || FT-Click, BASRouter LX, Onicon F-4300 || <br />
|-<br />
| B+ || A- || || || || || MBS UBR-01 Mk II || This is obviously contrary to everyone else <br />
|-<br />
| 485+ || 485- || || || Symbol || || FieldServer || <br />
|-<br />
| U+ || U- || || || || || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || || || || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || || || || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485], AirBox<br />
|-<br />
| A || B || || || || || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || || || || KMC router, A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=MS/TP_Troubleshooting&diff=13743MS/TP Troubleshooting2026-09-06T15:43:22Z<p>BACnetEd: </p>
<hr />
<div>This page is intended as a guide to troubleshooting BACnet MS/TP networks.<br />
<br />
{| class="wikitable"<br />
|+ Curated List of the most common problems<br />
|-<br />
! Votes !! Description <br />
|-<br />
| 1 || Improper grounding - device not grounded<br />
|-<br />
| 1 || Improper grounding - common not grounded with 100R resistor to ground<br />
|-<br />
| 1 || Improper grounding - Shield not terminated<br />
|-<br />
| 1 || Improper Baud rate setting<br />
|-<br />
| 1 || Duplicate MAC address on segment<br />
|-<br />
| 1 || MAC address set beyond Max_Masters<br />
|-<br />
| 1 || Excessive traffic due to polling activity<br />
|-<br />
| 1 || Excessive traffic due to broadcasts elsewhere on the network<br />
|-<br />
| 1 || One bad device brings down the whole network<br />
|}<br />
<br />
<br />
{| class="wikitable"<br />
|+ Troubleshooting Methods<br />
|-<br />
! Symptom !! Suggested Starting Point<br />
|-<br />
| I cannot see any devices on the MS/TP nework || Quiet Network Checklist<br />
|-<br />
| etc || Other<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=MS/TP_Troubleshooting&diff=13742MS/TP Troubleshooting2026-09-06T15:00:54Z<p>BACnetEd: </p>
<hr />
<div>This page is intended as a guide to troubleshooting BACnet MS/TP networks.<br />
<br />
{| class="wikitable"<br />
|+ Curated List of the most common problems<br />
|-<br />
! Votes !! Description <br />
|-<br />
| 1 || Improper grounding - device not grounded<br />
|-<br />
| 1 || Improper grounding - common not grounded with 100R resistor to ground<br />
|-<br />
| 1 || Improper grounding - Shield not terminated<br />
|-<br />
| 1 || Improper Baud rate setting<br />
|-<br />
| 1 || Duplicate MAC address on segment<br />
|-<br />
| 1 || MAC address set beyond Max_Masters<br />
|-<br />
| 1 || Excessive traffic due to polling activity<br />
|-<br />
| 1 || Excessive traffic due to broadcasts elsewhere on the network<br />
|-<br />
| 1 || One bad device brings down the whole network<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=MS/TP_Troubleshooting&diff=13741MS/TP Troubleshooting2026-09-06T14:58:37Z<p>BACnetEd: </p>
<hr />
<div>This page is intended as a guide to troubleshooting BACnet MS/TP networks.<br />
<br />
{| class="wikitable"<br />
|+ Curated List of the most common problems<br />
|-<br />
! Votes !! Description <br />
|-<br />
| 1 || Improper grounding - device not grounded<br />
|-<br />
| 1 || Improper grounding - common not grounded with 100R resistor to ground<br />
|-<br />
| 1 || Improper grounding - Shield not terminated<br />
|-<br />
| 1 || Improper Baud rate setting<br />
|-<br />
| 1 || Duplicate MAC address on segment<br />
|-<br />
| 1 || MAC address set beyond Max_Masters<br />
|-<br />
| 1 || Excessive traffic due to polling activity<br />
|-<br />
| 1 || Excessive traffic due to broadcasts elsewhere on the network<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=MS/TP_Troubleshooting&diff=13740MS/TP Troubleshooting2026-09-06T14:56:54Z<p>BACnetEd: Created page with "This page is intended as a guide to troubleshooting BACnet MS/TP networks. {| class="wikitable" |+ Curated List of the most common problems |- ! Votes !! Description |- | 1 || Improper grounding - device not grounded |- | 1 || Improper grounding - common not grounded with 100R resistor to ground |- | 1 || Improper grounding - Shield not terminated |}"</p>
<hr />
<div>This page is intended as a guide to troubleshooting BACnet MS/TP networks.<br />
<br />
{| class="wikitable"<br />
|+ Curated List of the most common problems<br />
|-<br />
! Votes !! Description <br />
|-<br />
| 1 || Improper grounding - device not grounded<br />
|-<br />
| 1 || Improper grounding - common not grounded with 100R resistor to ground<br />
|-<br />
| 1 || Improper grounding - Shield not terminated<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Main_Page&diff=13739Main Page2026-09-06T14:54:25Z<p>BACnetEd: </p>
<hr />
<div><big>'''The new BACnetWiki'''</big><br />
<br />
This is a reboot of the BACnet Wiki for consolidating thoughts and discussions around BACnet. Email me at '''edward@bac-test.com''' if needed<br />
<br />
'''Resources'''<br />
* [[BACnet Product Gallery]] - Equipment, tools, services<br />
* [[BACnet Developer Resources]] - for BACnet Stack programmers<br />
* [[BACnet User Resources]] - for those of us who use BACnet devices<br />
* [[Facilities Manager Resources]] - for those responsible for a site containing hundreds or thousands of BACnet devices<br />
* [[Resources for Beginners]]<br />
* [[Installer Resources]] - help with installing BACnet systems<br />
<!--- * [https://forum.bac-test.com/ BACnet discussion forum] --><br />
* The [[BACnet Standard]]<br />
* [[MS/TP Troubleshooting]]<br />
* [https://www.linkedin.com/groups/13566440/ BACnet Developers Group on LinkedIn]<br />
* [[BACnet Protocol]]<br />
* [[BIBBS - BACnet Interoperability Building Blocks]]<br />
* [[BACnet Services Supported]]<br />
* [[BACnet Addenda 135]]<br />
* [[BACnet Addenda 135.1]]<br />
* [[BACnet BTL Tests to final 135.1 Tracking]]<br />
* [[BACnet Interpretations]]<br />
* [[BTL Procedure | BTL Submittal Process]]<br />
* [[BTL Resources]]<br />
* [[BTL Test Commentary]]<br />
* [[BTL Implementation Guideline]]<br />
* Proposed [[Diagnostic Object]]<br />
* [[BACnet Best Practices]]<br />
* [[BACnet Protocol Wish List]]<br />
* [[BACnet MS/TP Best Practices]]<br />
* [[BACnet/T1L]]<br />
* [[RS-485 Polarity]]<br />
* [[BACnet Organizations]]<br />
* [[Book of Records]]</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Main_Page&diff=13738Main Page2026-09-06T14:54:01Z<p>BACnetEd: </p>
<hr />
<div><big>'''The new BACnetWiki'''</big><br />
<br />
This is a reboot of the BACnet Wiki for consolidating thoughts and discussions around BACnet. Email me at '''edward@bac-test.com''' if needed<br />
<br />
'''Resources'''<br />
* [[BACnet Product Gallery]] - Equipment, tools, services<br />
* [[BACnet Developer Resources]] - for BACnet Stack programmers<br />
* [[BACnet User Resources]] - for those of us who use BACnet devices<br />
* [[Facilities Manager Resources]] - for those responsible for a site containing hundreds or thousands of BACnet devices<br />
* [[Resources for Beginners]]<br />
* [[Installer Resources]] - help with installing BACnet systems<br />
<!--- * [https://forum.bac-test.com/ BACnet discussion forum] --><br />
* The [[BACnet Standard]]<br />
* [MS/TP Troubleshooting]<br />
* [https://www.linkedin.com/groups/13566440/ BACnet Developers Group on LinkedIn]<br />
* [[BACnet Protocol]]<br />
* [[BIBBS - BACnet Interoperability Building Blocks]]<br />
* [[BACnet Services Supported]]<br />
* [[BACnet Addenda 135]]<br />
* [[BACnet Addenda 135.1]]<br />
* [[BACnet BTL Tests to final 135.1 Tracking]]<br />
* [[BACnet Interpretations]]<br />
* [[BTL Procedure | BTL Submittal Process]]<br />
* [[BTL Resources]]<br />
* [[BTL Test Commentary]]<br />
* [[BTL Implementation Guideline]]<br />
* Proposed [[Diagnostic Object]]<br />
* [[BACnet Best Practices]]<br />
* [[BACnet Protocol Wish List]]<br />
* [[BACnet MS/TP Best Practices]]<br />
* [[BACnet/T1L]]<br />
* [[RS-485 Polarity]]<br />
* [[BACnet Organizations]]<br />
* [[Book of Records]]</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Peer_Transfer_Object&diff=13737Peer Transfer Object2026-09-04T14:49:27Z<p>BACnetEd: </p>
<hr />
<div>This is a proof-of-concept project in preparation for submitting a new "Peer Transfer Object" proposal to the BACnet Steering Committee<br />
<br />
See the Wiki overview of [[Diagnostic Features]], and related [[Diagnostic Services]]<br />
<br />
{| class="wikitable"<br />
|+ Peer Transfer Object (one per device)<br />
|-<br />
! Property !! Req !! New !! Datatype !! Description<br />
|-<br />
| ObjectID ID || R || N || BACnetObjectID || Mandatory for every BACnet Object<br />
|-<br />
| Compression Enabled || O || Y || Boolean || Schema based / Varint choices of on the wire packets<br />
|-<br />
|}<br />
<br />
<br />
'''Initial Ideas'''<br />
<br />
'''Site-wide'''<br />
<br />
<!--<br />
<br />
bpr1304 - https://drive.google.com/drive/u/0/folders/1QCOeVpfFPL4KIZbRWUXPr2NqbKo5qrOQ <br />
<br />
--></div>BACnetEdhttp://bacnetwiki.com/index.php?title=BACnet_MS/TP&diff=13736BACnet MS/TP2026-09-04T14:48:05Z<p>BACnetEd: Created page with "BACnet MS/TP - or "Mulitdrop Serial Bus / Token Passing" is a RS-485 physical layer designed to support multiple devices sharing a RS-485 bus. It is primarily used for small controllers such as for VAVs, RTUs, sensors or actuators. The language has changed to avoid the derogatory Master-Slave/Token Passing used in the past, but it will take a while for the industry to migrate from this embedded use of the language."</p>
<hr />
<div>BACnet MS/TP - or "Mulitdrop Serial Bus / Token Passing" is a RS-485 physical layer designed to support multiple devices sharing a RS-485 bus. It is primarily used for small controllers such as for VAVs, RTUs, sensors or actuators.<br />
<br />
The language has changed to avoid the derogatory Master-Slave/Token Passing used in the past, but it will take a while for the industry to migrate from this embedded use of the language.</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BACnet_Datalinks&diff=13735BACnet Datalinks2026-09-04T14:43:43Z<p>BACnetEd: </p>
<hr />
<div>{| class="wikitable"<br />
|+ BACnet Datalinks<br />
|-<br />
! Datalink !! Physical Medium !! Description !! Status<br />
|-<br />
| [[BACnet MS/TP]] || RS-485 || Master Slave / Token Passing || Active<br />
|-<br />
| BACnet/IP|| TCP/IP over Ethernet || || Active<br />
|-<br />
| PTP || RS-232 || Peer-to-Peer || <br />
|-<br />
| Ethernet || Ethernet || Note - "Ethernet", not IP || Active<br />
|-<br />
| AB || IP || BACnet Secure Connect / BACnet/SC || <br />
|-<br />
| 8 || ARCNET || ARCNET (ATA 878.1) || <br />
|-<br />
| 10 || RS-232 || PTP (Peer-to-Peer) || <br />
|-<br />
| 11 || Lon || LonTalk (ISO/IEC 14908.1) || <br />
|-<br />
| U || IPv6 || BACnet/IPv6 || <br />
|-<br />
| O || Zigbee || ZigBee || <br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BACnet_Vendor_ID_List&diff=13734BACnet Vendor ID List2026-08-18T10:44:11Z<p>BACnetEd: Created page with "The official BACnet Vendor ID list can be found on the BACnet.org website [https://bacnet.org/assigned-vendor-ids/ link]"</p>
<hr />
<div>The official BACnet Vendor ID list can be found on the BACnet.org website [https://bacnet.org/assigned-vendor-ids/ link]</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Peer_Transfer_Object&diff=13733Peer Transfer Object2026-08-18T08:55:29Z<p>BACnetEd: </p>
<hr />
<div>This is a proof-of-concept project in preparation for submitting a new "Peer Transfer Object" proposal to the BACnet Steering Committee<br />
<br />
See the Wiki overview of [[Diagnostic Features]], and related [[Diagnostic Services]]<br />
<br />
{| class="wikitable"<br />
|+ Peer Transfer Object (one per device)<br />
|-<br />
! Property !! Req !! New !! Datatype !! Description<br />
|-<br />
| ObjectID ID || R || N || BACnetObjectID || Mandatory for every BACnet Object<br />
|-<br />
| Compression Enabled || O || Y || Boolean || Schema based / Varint choices of on the wire packets<br />
|-<br />
|}<br />
<br />
<br />
'''Initial Ideas'''<br />
<br />
'''Site-wide'''</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BTL_Procedure&diff=13732BTL Procedure2026-08-16T13:26:36Z<p>BACnetEd: </p>
<hr />
<div>Here is a summary/checklist to get your device through the BTL certification process:<br />
<br />
* Pre-test your device using our BACnet Test Suite<br />
* Contact the 4 labs, ([https://btl.org/device-testing/#provider-section link here]) let them know that you are interested, confirm they can test your IUT (Implementation Under Test)<br />
* Confirm they will test to Protocol Revision 26 (or perhaps higher)<br />
* Confirm they will provide an estimate (quote) based on the "BTL Functionality Checklist" that you will fill in<br />
* Find out when they can start testing, and estimate how long will it take<br />
* Confirm Payment terms<br />
* Ask for any other requirements they may have<br />
* Complete the "BTL Functionality Checklist". The original is in the "BTL Test Package-26" which can be downloaded from the BTL website<br />
* Send this to the candidate lab(s) and get a final estimate of the costs<br />
* Contact BTL themselves and let them know your intent to start testing with the selected Lab, and ask them to initiate procedures for eventual registration. Someone, not sure who, I think BTL, will issue a TCxxxxxx number for tracking purposes.<br />
* Pay the $750 (?) registration fee.<br />
* Ask BTL for additional guidance<br />
* There will be additional fees for the "Certification" and "Listing". (You probably do want to be "Listed" on the BTL website (link) for marketing purposes (this link is well referenced by users). But you are able to proceed with just the certificate if desired).<br />
* Select a Lab, proceed<br />
* [https://www.bac-test.com/ BITS] can assist you with this process.<br />
* (Optional) submit Test Results to [https://wspcert.de/en/welcome WSPCert] for certification.<br />
<br />
<br />
<!--<br />
Then the BTL paperwork has to be prepared and submitted. <br />
<br />
This process can take a few days of effort. <br />
<br />
However, in less than a day enough paperwork can be completed to submit a "Checklist" for the BACnet Profile (B-ASC) (BACnet Application Specific Controller) - this Checklist will allow the 4 candidate test laboratories (RBTO) to submit an estimate of time and cost to test, as well as a schedule for start and completion.<br />
<br />
BTL FeesYou will need to pay an application fee ($750) to get going. <br />
<br />
Testing for a B-ASC typically can be done in about 3 weeks. <br />
<br />
So the RBTOs will quote, at a wild guess, about $10-20K, (with Onicon's BACnet International membership discount), final estimate will be provided per the procedure above, and final amount will be how well we do in testing.<br />
<br />
Preparation<br />
<br />
Pay the application fee ($750)<br />
Prepare the Checklist<br />
Get 4 estimatesSelect RBTO (test lab) and enter into a contract with them. <br />
This sets the start date and is a good idea to get this settled quickly. It can always slide later, but the queue can be from 0 to 3 months.<br />
Prepare final paperwork (Test Plan, PICS, EPICS)Prepare equipment and ship to test lab<br />
Help RBTO get set upInteract with RBTO and supply firmware updates when problems found - according to RBTO scheduleFinalize testing<br />
Finalize paperworkSubmit final test report to BTL and WSPCert for formal certification.<br />
<br />
Total cost, Rough order of Magnitude will be:<br />
Prep (me) approx $7500<br />
BI Membership $5500 - but you are already members so $0<br />
RBTO fees $10-20<br />
KMy debugging support, hopefully minimal, but I will put in a week, approx $7500<br />
Finalization of paperwork, certs, my time, approx $3000<br />
Final BTL fees for listing, WSPCert, approx $2000 (from memory)<br />
<br />
So, total, both BITS and BTL fees included, somewhere between $20K if all goes well to $39K if there are bumps in the road. and 1 to 4 months elapsed.<br />
--></div>BACnetEdhttp://bacnetwiki.com/index.php?title=BTL_Procedure&diff=13731BTL Procedure2026-08-16T13:15:55Z<p>BACnetEd: </p>
<hr />
<div>Here is a summary/checklist to get your device through the BTL certification process:<br />
<br />
* Pre-test your device using our BACnet Test Suite<br />
* Contact the 4 labs, ([https://btl.org/device-testing/#provider-section link here]) let them know that you are interested, confirm they can test your IUT (Implementation Under Test)<br />
* Confirm they will test to Protocol Revision 26 (or perhaps higher)<br />
* Confirm they will provide an estimate (quote) based on the "BTL Functionality Checklist" that you will fill in<br />
* Find out when they can start testing, and estimate how long will it take<br />
* Confirm Payment terms<br />
* Ask for any other requirements they may have<br />
* Complete the "BTL Functionality Checklist". The original is in the "BTL Test Package-26" which can be downloaded from the BTL website<br />
* Send this to the candidate lab(s) and get a final estimate of the costs<br />
* Contact BTL themselves and let them know your intent to start testing with the selected Lab, and ask them to initiate procedures for eventual registration. Someone, not sure who, I think BTL, will issue a TCxxxxxx number for tracking purposes.<br />
* Pay the $750 (?) registration fee.<br />
* Ask BTL for additional guidance<br />
* There will be additional fees for the "Certification" and "Listing". (You probably do want to be "Listed" on the BTL website (link) for marketing purposes (this link is well referenced by users). But you are able to proceed with just the certificate if desired).<br />
* Select a Lab, proceed<br />
* [https://www.bac-test.com/ BITS] can assist you with this process.<br />
* (Optional) submit Test Results to [https://wspcert.de/en/welcome WSPCert] for certification.</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BTL_Procedure&diff=13730BTL Procedure2026-08-16T13:12:10Z<p>BACnetEd: </p>
<hr />
<div>Here is a summary/checklist to get your device through the BTL certification process:<br />
<br />
* Pre-test your device using our BACnet Test Suite<br />
* Contact the 4 labs, ([https://btl.org/device-testing/#provider-section link here]) let them know that you are interested, confirm they can test your IUT (Implementation Under Test)<br />
* Confirm they will test to Protocol Revision 26 (or perhaps higher)<br />
* Confirm they will provide an estimate (quote) based on the "BTL Functionality Checklist" that you will fill in<br />
* Find out when they can start testing, and estimate how long will it take<br />
* Confirm Payment terms<br />
* Ask for any other requirements they may have<br />
* Complete the "BTL Functionality Checklist". The original is in the "BTL Test Package-26" which can be downloaded from the BTL website<br />
* Send this to the candidate lab(s) and get a final estimate of the costs<br />
* Contact BTL themselves and let them know your intent to start testing with the selected Lab, and ask them to initiate procedures for eventual registration. Someone, not sure who, I think BTL, will issue a TCxxxxxx number for tracking purposes.<br />
* Ask BTL for additional guidance<br />
* There will be additional fees for the "Certification" and "Listing". (You probably do want to be "Listed" on the BTL website (link) for marketing purposes (this link is well referenced by users). But you are able to proceed with just the certificate if desired).<br />
* Select a Lab, proceed<br />
* [https://www.bac-test.com/ BITS] can assist you with this process.<br />
* (Optional) submit Test Results to [https://wspcert.de/en/welcome WSPCert] for certification.</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Peer_Transfer_Object&diff=13729Peer Transfer Object2026-08-15T13:15:20Z<p>BACnetEd: Created page with "This is a proof-of-concept project in preparation for submitting a new "Peer Transfer Object" proposal to the BACnet Steering Committee See the Wiki overview of Diagnostic Features, and related Diagnostic Services {| class="wikitable" |+ Peer Transfer Object (one per device) |- ! Property !! Req !! New !! Datatype !! Description |- | BACnet Stack Vendor ID || O || || Unsigned || Different to the Vendor ID of the device itself if 3rd party stack |- | BACnet Stac..."</p>
<hr />
<div>This is a proof-of-concept project in preparation for submitting a new "Peer Transfer Object" proposal to the BACnet Steering Committee<br />
<br />
See the Wiki overview of [[Diagnostic Features]], and related [[Diagnostic Services]]<br />
<br />
{| class="wikitable"<br />
|+ Peer Transfer Object (one per device)<br />
|-<br />
! Property !! Req !! New !! Datatype !! Description<br />
|-<br />
| BACnet Stack Vendor ID || O || || Unsigned || Different to the Vendor ID of the device itself if 3rd party stack<br />
|-<br />
| BACnet Stack Library Version || O || Y || String || This is the version of the 3rd party library<br />
|-<br />
| BACnet Stack Version || R || Y || String || OEM may modify the above, this needs to be versioned. Else if OEM custom, that version<br />
|-<br />
| Controller Firmware Version || R || N || String || This is the version of controllers 'business logic'<br />
|-<br />
| Application Version || O || N || String || This is the version of user configurable programs, scripts or logic'<br />
|-<br />
| BTL Certificate # || O || Y || String || <br />
|-<br />
| BTL Issue Date || O || Y || BACnetDate ||<br />
|-<br />
| RAM % || || || || <br />
|-<br />
| Program memory % || || || || <br />
|-<br />
| CPU load % || || || || <br />
|-<br />
| Temperature || || || || <br />
|-<br />
| Certificate expiration dates || || || || <br />
|}<br />
<br />
<br />
'''Initial Ideas'''<br />
<br />
'''Site-wide'''<br />
<br />
* Duplicate Device ID detected<br />
* Looped Route (Jen’s words)<br />
<br />
<br />
'''System'''<br />
<br />
* An array/list of strings (and values) to display error messages<br />
* - repetition count<br />
* - priority<br />
* - non-repeating<br />
* - suppressible<br />
* - ack required<br />
* - delete (once, forever)<br />
* - filters (same as suppressible?)<br />
* - features similar to existing alarms/event buffers/remote destinations (code-share)<br />
* ESE ?<br />
* flasherr ?<br />
* Enforced version numbering (including bug/feature/eng/market)<br />
<br />
<br />
'''Control'''<br />
<br />
* Debug / production mode at runtime<br />
* Debug verbosity levels<br />
* ‘C or ‘F system-wide<br />
* Developer mode flag (with password?)<br />
<br />
<br />
'''Routing'''<br />
<br />
* High-water queue usage<br />
* Duplicate Network Numbers<br />
* Broadcast storm (loop) detected / suppressed ([[Circular Route Detection]])<br />
* Monitoring remote connections (devices)<br />
* Attempts made<br />
* Passes / fails / MTTR etc.<br />
<br />
<br />
'''General Datalink'''<br />
<br />
* Messages per second (minute/hour)<br />
* queue sizes, high-water, choked/ message rate<br />
<br />
<br />
'''IP Datalinks'''<br />
<br />
* Duplicate IP address<br />
* Netmask Error<br />
<br />
'''MS/TP Datalinks'''<br />
<br />
* Measure Tusage (token handling time)<br />
<br />
'''Justifications'''<br />
<br />
* Enhanced Monitoring and Troubleshooting: A standardized way to monitor the health and status of devices, systems, and networks. It allows for real-time visibility into potential issues, which can aid in troubleshooting and reducing downtime.<br />
* Proactive Maintenance: By collecting and analyzing diagnostic data, building managers can identify issues before they escalate into significant problems. This proactive approach to maintenance can minimize disruptions, extend the lifespan of equipment, and reduce repair costs.<br />
* Integration and Interoperability: BACnet is designed to facilitate interoperability between various building automation systems and devices. By defining a standardized diagnostic object, different devices and systems can share diagnostic information more effectively, regardless of the manufacturer.<br />
* Reduced Downtime: Swift identification and resolution of issues through diagnostic data can significantly reduce downtime of critical systems, leading to improved operational continuity and tenant satisfaction.</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Diagnostic_Object&diff=13728Diagnostic Object2026-08-15T13:13:43Z<p>BACnetEd: </p>
<hr />
<div>This is a proof-of-concept project in preparation for submitting a new "BACnet Diagnostic Object" proposal to the BACnet Steering Committee<br />
<br />
See the Wiki overview of [[Diagnostic Features]], and related [[Diagnostic Services]]<br />
<br />
{| class="wikitable"<br />
|+ BACnet Diagnostic Object (one per device)<br />
|-<br />
! Property !! Req !! New !! Datatype !! Description<br />
|-<br />
| BACnet Stack Vendor ID || O || || Unsigned || Different to the Vendor ID of the device itself if 3rd party stack<br />
|-<br />
| BACnet Stack Library Version || O || Y || String || This is the version of the 3rd party library<br />
|-<br />
| BACnet Stack Version || R || Y || String || OEM may modify the above, this needs to be versioned. Else if OEM custom, that version<br />
|-<br />
| Controller Firmware Version || R || N || String || This is the version of controllers 'business logic'<br />
|-<br />
| Application Version || O || N || String || This is the version of user configurable programs, scripts or logic'<br />
|-<br />
| BTL Certificate # || O || Y || String || <br />
|-<br />
| BTL Issue Date || O || Y || BACnetDate ||<br />
|-<br />
| RAM % || || || || <br />
|-<br />
| Program memory % || || || || <br />
|-<br />
| CPU load % || || || || <br />
|-<br />
| Temperature || || || || <br />
|-<br />
| Certificate expiration dates || || || || <br />
|}<br />
<br />
<br />
'''Initial Ideas'''<br />
<br />
'''Site-wide'''<br />
<br />
* Duplicate Device ID detected<br />
* Looped Route (Jen’s words)<br />
<br />
<br />
'''System'''<br />
<br />
* An array/list of strings (and values) to display error messages<br />
* - repetition count<br />
* - priority<br />
* - non-repeating<br />
* - suppressible<br />
* - ack required<br />
* - delete (once, forever)<br />
* - filters (same as suppressible?)<br />
* - features similar to existing alarms/event buffers/remote destinations (code-share)<br />
* ESE ?<br />
* flasherr ?<br />
* Enforced version numbering (including bug/feature/eng/market)<br />
<br />
<br />
'''Control'''<br />
<br />
* Debug / production mode at runtime<br />
* Debug verbosity levels<br />
* ‘C or ‘F system-wide<br />
* Developer mode flag (with password?)<br />
<br />
<br />
'''Routing'''<br />
<br />
* High-water queue usage<br />
* Duplicate Network Numbers<br />
* Broadcast storm (loop) detected / suppressed ([[Circular Route Detection]])<br />
* Monitoring remote connections (devices)<br />
* Attempts made<br />
* Passes / fails / MTTR etc.<br />
<br />
<br />
'''General Datalink'''<br />
<br />
* Messages per second (minute/hour)<br />
* queue sizes, high-water, choked/ message rate<br />
<br />
<br />
'''IP Datalinks'''<br />
<br />
* Duplicate IP address<br />
* Netmask Error<br />
<br />
'''MS/TP Datalinks'''<br />
<br />
* Measure Tusage (token handling time)<br />
<br />
'''Justifications'''<br />
<br />
* Enhanced Monitoring and Troubleshooting: A standardized way to monitor the health and status of devices, systems, and networks. It allows for real-time visibility into potential issues, which can aid in troubleshooting and reducing downtime.<br />
* Proactive Maintenance: By collecting and analyzing diagnostic data, building managers can identify issues before they escalate into significant problems. This proactive approach to maintenance can minimize disruptions, extend the lifespan of equipment, and reduce repair costs.<br />
* Integration and Interoperability: BACnet is designed to facilitate interoperability between various building automation systems and devices. By defining a standardized diagnostic object, different devices and systems can share diagnostic information more effectively, regardless of the manufacturer.<br />
* Reduced Downtime: Swift identification and resolution of issues through diagnostic data can significantly reduce downtime of critical systems, leading to improved operational continuity and tenant satisfaction.</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Test&diff=13727Test2026-08-01T16:42:53Z<p>BACnetEd: Created page with "{| class="wikitable sortable filterable" ! Product ! Manufacturer ! Category ! Status ! Priority ! Date reported |- | ASI IntelliFront | ASI Controls | Controller | Open | High | 2026-07-21 |- | PXC4 | Siemens | Controller | Closed | Medium | 2026-06-15 |- | CIPer 50 | Honeywell | Controller | Investigating | High | 2026-07-30 |- | Automation Server | Schneider Electric | Supervisor | Open | Low | 2026-05-12 |- | JACE 9000 | Tridium | Supervisor | Closed | Medium | 2026-..."</p>
<hr />
<div>{| class="wikitable sortable filterable"<br />
! Product<br />
! Manufacturer<br />
! Category<br />
! Status<br />
! Priority<br />
! Date reported<br />
|-<br />
| ASI IntelliFront<br />
| ASI Controls<br />
| Controller<br />
| Open<br />
| High<br />
| 2026-07-21<br />
|-<br />
| PXC4<br />
| Siemens<br />
| Controller<br />
| Closed<br />
| Medium<br />
| 2026-06-15<br />
|-<br />
| CIPer 50<br />
| Honeywell<br />
| Controller<br />
| Investigating<br />
| High<br />
| 2026-07-30<br />
|-<br />
| Automation Server<br />
| Schneider Electric<br />
| Supervisor<br />
| Open<br />
| Low<br />
| 2026-05-12<br />
|-<br />
| JACE 9000<br />
| Tridium<br />
| Supervisor<br />
| Closed<br />
| Medium<br />
| 2026-04-09<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=135.1_-_13.1.2_TD_Initiated_Unsegmented_Request_and_Segmented_Response_(Non-Window)&diff=13726135.1 - 13.1.2 TD Initiated Unsegmented Request and Segmented Response (Non-Window)2026-07-23T12:47:41Z<p>BACnetEd: Created page with "This test is considered invalid. Test 13.1.2 from 135.1 contradicts the BACnet standard. According to Clause 5.4.5.4 of the BACnet standard: === UnexpectedPDU_Received If an unexpected PDU (BACnet-Confirmed-Request-PDU) that is secured with the same settings as the original PDU is received from the network layer, then stop SegmentTimer; issue an N-UNITDATA.request with 'data_expecting_reply' = FALSE to transmit a BACnet-Abort-PDU with 'server' = TRUE; and enter the ID..."</p>
<hr />
<div>This test is considered invalid.<br />
<br />
<br />
Test 13.1.2 from 135.1 contradicts the BACnet standard. According<br />
to Clause 5.4.5.4 of the BACnet standard:<br />
===<br />
UnexpectedPDU_Received<br />
If an unexpected PDU (BACnet-Confirmed-Request-PDU) that is secured with<br />
the same settings as the original PDU is received from the network<br />
layer,<br />
<br />
then stop SegmentTimer; issue an N-UNITDATA.request with<br />
'data_expecting_reply' = FALSE to transmit a<br />
BACnet-Abort-PDU with 'server' = TRUE; and enter the IDLE state.<br />
===<br />
<br />
Note that the standard does not have the DuplicateRequestReceived event<br />
in the SEGMENTED_RESPONSE state, so it is UnexpectedPDU_Received, which<br />
sends BACnet-Abort-PDU.</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BTL_Test_Commentary&diff=13725BTL Test Commentary2026-07-23T12:47:23Z<p>BACnetEd: </p>
<hr />
<div>{| class="wikitable"<br />
|+ 135.1 Tests and comments <br />
|-<br />
! 135.1 Test !! BTL Test !! Description !! Notes !! Detail<br />
|-<br />
| 13.1.2 || || TD Initiated Unsegmented Request and Segmented Response (Non-Window) || This test does not reflect the 135 standard, and is invalid. || [[135.1 - 13.1.2 TD Initiated Unsegmented Request and Segmented Response (Non-Window) | link ]]<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BTL_Test_Commentary&diff=13724BTL Test Commentary2026-07-23T12:41:58Z<p>BACnetEd: </p>
<hr />
<div>{| class="wikitable"<br />
|+ 135.1 Tests and comments<br />
|-<br />
! 135.1 Test !! BTL Test !! Description !! Notes<br />
|-<br />
| 13.1.2 || || TD Initiated Unsegmented Request and Segmented Response (Non-Window) || This test does not reflect the 135 standard, and is invalid.<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BTL_Test_Commentary&diff=13723BTL Test Commentary2026-07-23T12:41:16Z<p>BACnetEd: Created page with "{| class="wikitable" |+ 135.1 Tests and comments |- ! 135.1 Test !! BTL Test !! Notes |- | 13.1.2 TD Initiated Unsegmented Request and Segmented Response (Non-Window) || || This test does not reflect the 135 standard, and is invalid. |}"</p>
<hr />
<div>{| class="wikitable"<br />
|+ 135.1 Tests and comments<br />
|-<br />
! 135.1 Test !! BTL Test !! Notes<br />
|-<br />
| 13.1.2 TD Initiated Unsegmented Request and Segmented Response (Non-Window) || || This test does not reflect the 135 standard, and is invalid.<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Main_Page&diff=13722Main Page2026-07-23T12:39:38Z<p>BACnetEd: </p>
<hr />
<div><big>'''The new BACnetWiki'''</big><br />
<br />
This is a reboot of the BACnet Wiki for consolidating thoughts and discussions around BACnet. Email me at '''edward@bac-test.com''' if needed<br />
<br />
'''Resources'''<br />
* [[BACnet Product Gallery]] - Equipment, tools, services<br />
* [[BACnet Developer Resources]] - for BACnet Stack programmers<br />
* [[BACnet User Resources]] - for those of us who use BACnet devices<br />
* [[Facilities Manager Resources]] - for those responsible for a site containing hundreds or thousands of BACnet devices<br />
* [[Resources for Beginners]]<br />
* [[Installer Resources]] - help with installing BACnet systems<br />
<!--- * [https://forum.bac-test.com/ BACnet discussion forum] --><br />
* The [[BACnet Standard]]<br />
* [https://www.linkedin.com/groups/13566440/ BACnet Developers Group on LinkedIn]<br />
* [[BACnet Protocol]]<br />
* [[BIBBS - BACnet Interoperability Building Blocks]]<br />
* [[BACnet Services Supported]]<br />
* [[BACnet Addenda 135]]<br />
* [[BACnet Addenda 135.1]]<br />
* [[BACnet BTL Tests to final 135.1 Tracking]]<br />
* [[BACnet Interpretations]]<br />
* [[BTL Procedure | BTL Submittal Process]]<br />
* [[BTL Resources]]<br />
* [[BTL Test Commentary]]<br />
* [[BTL Implementation Guideline]]<br />
* Proposed [[Diagnostic Object]]<br />
* [[BACnet Best Practices]]<br />
* [[BACnet Protocol Wish List]]<br />
* [[BACnet MS/TP Best Practices]]<br />
* [[BACnet/T1L]]<br />
* [[RS-485 Polarity]]<br />
* [[BACnet Organizations]]<br />
* [[Book of Records]]</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BACnet/T1L&diff=13721BACnet/T1L2026-07-03T08:44:00Z<p>BACnetEd: Created page with ""BACnet/T1L is NOT a BACnet standard, it is simply BACnet/IP (or BACnet/SC) over a 10BASE-T1L datalink. 10BASE-T1L is also "simple" Ethernet over a twisted pair, or SPE (Single Pair Ethernet) 10BASE-T1L has great potential in Building Automation due to the fact that twisted pair is common, well known in the industry, and there is the possibility of re-using in-place or legacy network wiring. As such, here is a list of Building Automation / BACnet resources that are r..."</p>
<hr />
<div>"BACnet/T1L is NOT a BACnet standard, it is simply BACnet/IP (or BACnet/SC) over a 10BASE-T1L datalink. 10BASE-T1L is also "simple" Ethernet over a twisted pair, or SPE (Single Pair Ethernet)<br />
<br />
<br />
10BASE-T1L has great potential in Building Automation due to the fact that twisted pair is common, well known in the industry, and there is the possibility of re-using in-place or legacy network wiring.<br />
<br />
<br />
As such, here is a list of Building Automation / BACnet resources that are relevant to BACnet<br />
<br />
<br />
{| class="wikitable"<br />
|+ Caption text<br />
|-<br />
! Header text !! Header text !! Header text !! Header text<br />
|-<br />
| Example || Example || Example || Example<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Main_Page&diff=13720Main Page2026-07-03T08:39:15Z<p>BACnetEd: </p>
<hr />
<div><big>'''The new BACnetWiki'''</big><br />
<br />
This is a reboot of the BACnet Wiki for consolidating thoughts and discussions around BACnet. Email me at '''edward@bac-test.com''' if needed<br />
<br />
'''Resources'''<br />
* [[BACnet Product Gallery]] - Equipment, tools, services<br />
* [[BACnet Developer Resources]] - for BACnet Stack programmers<br />
* [[BACnet User Resources]] - for those of us who use BACnet devices<br />
* [[Facilities Manager Resources]] - for those responsible for a site containing hundreds or thousands of BACnet devices<br />
* [[Resources for Beginners]]<br />
* [[Installer Resources]] - help with installing BACnet systems<br />
<!--- * [https://forum.bac-test.com/ BACnet discussion forum] --><br />
* The [[BACnet Standard]]<br />
* [https://www.linkedin.com/groups/13566440/ BACnet Developers Group on LinkedIn]<br />
* [[BACnet Protocol]]<br />
* [[BIBBS - BACnet Interoperability Building Blocks]]<br />
* [[BACnet Services Supported]]<br />
* [[BACnet Addenda 135]]<br />
* [[BACnet Addenda 135.1]]<br />
* [[BACnet BTL Tests to final 135.1 Tracking]]<br />
* [[BACnet Interpretations]]<br />
* [[BTL Procedure | BTL Submittal Process]]<br />
* [[BTL Resources]]<br />
* [[BTL Test Plan]]<br />
* [[BTL Implementation Guideline]]<br />
* Proposed [[Diagnostic Object]]<br />
* [[BACnet Best Practices]]<br />
* [[BACnet Protocol Wish List]]<br />
* [[BACnet MS/TP Best Practices]]<br />
* [[BACnet/T1L]]<br />
* [[RS-485 Polarity]]<br />
* [[BACnet Organizations]]<br />
* [[Book of Records]]</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Vendors_-_BACnet_Routers&diff=13719Vendors - BACnet Routers2026-07-01T09:44:53Z<p>BACnetEd: Created page with "{| class="wikitable" |+ BACnet Router Vendors |- ! Vendor !! Model !! Description !! BACnet/SC Hub !! Link |- | Contemporarty Controls || BASrouterSX || || [https://www.ccontrols.com/basautomation/basroutersx.php link] |- | Contemporarty Controls || BASrouter || || [https://www.ccontrols.com/basautomation/basrouter.php link] |- | MSA || FS-ROUTER-BAC2 || || [https://gb.msasafety.com/IIoT-Gateways/System-Integrators/BACnet-Router/p/bacnet-router?locale=en link] |- | KMC..."</p>
<hr />
<div>{| class="wikitable"<br />
|+ BACnet Router Vendors<br />
|-<br />
! Vendor !! Model !! Description !! BACnet/SC Hub !! Link<br />
|-<br />
| Contemporarty Controls || BASrouterSX || || [https://www.ccontrols.com/basautomation/basroutersx.php link]<br />
|-<br />
| Contemporarty Controls || BASrouter || || [https://www.ccontrols.com/basautomation/basrouter.php link]<br />
|-<br />
| MSA || FS-ROUTER-BAC2 || || [https://gb.msasafety.com/IIoT-Gateways/System-Integrators/BACnet-Router/p/bacnet-router?locale=en link]<br />
|-<br />
| KMC || BAC-5051AE || || [https://www.kmccontrols.com/product/62509/ link]<br />
|-<br />
| MBS || UBR-01 Mk II || || [https://en.mbs-solutions.de/ubr-01-mk-ii-bacnet-router link]<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BACnet_Product_Gallery&diff=13718BACnet Product Gallery2026-07-01T09:35:03Z<p>BACnetEd: </p>
<hr />
<div>{| class="wikitable"<br />
|+ Caption text<br />
|-<br />
! Model !! Description !! BTL !! Vendor !! Contact (email)<br />
|-<br />
| BTS || BACnet Test Suite - aimed at manufacturers || No || BITS || edward at bac-test.com<br />
|-<br />
| BSA || BACnet Site Auditor - Scans a site, identifying problems || No || BITS || edward at bac-test.com<br />
|-<br />
| [[Vendors - BACnet Routers|BACnet Routers]] || Links to a new page || Yes || Various || <br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13717RS-485 Polarity2026-06-26T20:37:43Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Class !! Manufacturer examples !!<br />
|-<br />
| A || B || Nominal || BITS, FieldServer<br />
|-<br />
| + || - || Symbol || BACnet Specification || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| RT+ || RT- || || EnOcean SmartServer IoT<br />
|-<br />
| + || - || Symbol || FT-Click, BASRouter LX, Onicon F-4300<br />
|-<br />
| B+ || A- || || MBS UBR-01 Mk II || This is obviously contrary to everyone else <br />
|-<br />
| 485+ || 485- || Symbol || FieldServer<br />
|-<br />
| U+ || U- || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485], AirBox<br />
|-<br />
| A || B || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || KMC router, A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Binary 0<br />
|-<br />
| 0 || A < B || Space || Off || Binary 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13716RS-485 Polarity2026-06-26T20:32:34Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Specification !! Description !! Terminology !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Class !! Manufacturer examples !!<br />
|-<br />
| A || B || Nominal || BITS, FieldServer<br />
|-<br />
| + || - || Symbol || BACnet Specification || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| RT+ || RT- || || EnOcean SmartServer IoT<br />
|-<br />
| + || - || Symbol || FT-Click, BASRouter LX, Onicon F-4300<br />
|-<br />
| B+ || A- || || MBS UBR-01 Mk II || This is obviously contrary to everyone else <br />
|-<br />
| 485+ || 485- || Symbol || FieldServer<br />
|-<br />
| U+ || U- || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485], AirBox<br />
|-<br />
| A || B || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || KMC router, A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Logic 0<br />
|-<br />
| 0 || A < B || Space || Off || Logic 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13715RS-485 Polarity2026-06-26T20:31:40Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. Further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Quotations directly from the Standerd. Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
* "The logic function of the generator and the receiver is beyond the scope of this standard, and therefore not defined"<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Our Terminology !! Description !! Terminonlogy !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Class !! Manufacturer examples !!<br />
|-<br />
| A || B || Nominal || BITS, FieldServer<br />
|-<br />
| + || - || Symbol || BACnet Specification || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| RT+ || RT- || || EnOcean SmartServer IoT<br />
|-<br />
| + || - || Symbol || FT-Click, BASRouter LX, Onicon F-4300<br />
|-<br />
| B+ || A- || || MBS UBR-01 Mk II || This is obviously contrary to everyone else <br />
|-<br />
| 485+ || 485- || Symbol || FieldServer<br />
|-<br />
| U+ || U- || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485], AirBox<br />
|-<br />
| A || B || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || KMC router, A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Logic 0<br />
|-<br />
| 0 || A < B || Space || Off || Logic 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13714RS-485 Polarity2026-06-22T09:28:33Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. A lot of further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Our Terminology !! Description !! Terminonlogy !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Class !! Manufacturer examples !!<br />
|-<br />
| A || B || Nominal || BITS, FieldServer<br />
|-<br />
| + || - || Symbol || BACnet Specification || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| RT+ || RT- || || EnOcean SmartServer IoT<br />
|-<br />
| + || - || Symbol || FT-Click, BASRouter LX, Onicon F-4300<br />
|-<br />
| B+ || A- || || MBS UBR-01 Mk II || This is obviously contrary to everyone else <br />
|-<br />
| 485+ || 485- || Symbol || FieldServer<br />
|-<br />
| U+ || U- || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485], AirBox<br />
|-<br />
| A || B || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || KMC router, A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Logic 0<br />
|-<br />
| 0 || A < B || Space || Off || Logic 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=RS-485_Polarity&diff=13713RS-485 Polarity2026-06-22T09:28:05Z<p>BACnetEd: </p>
<hr />
<div>RS-485 comprises two signals, one that 'tracks' the UART logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The meaning of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. A lot of further confusion arises when one considers the UART logic levels vs signal levels and labels. This article attempts to resolve the status, hopefully without adding to the confusion.<br />
<br />
'''Basic Rule from the specification (and I have the actual specification)<br />
<br />
* A > B means "binary 0 on the bus" or "ON".<br />
* A < B means "binary 1 on the bus" or "OFF".<br />
<br />
And A is non-inverting (and thus B is inverting)<br />
<br />
'''Identifying 'A' and 'B' signals'''<br />
<br />
Remember that UARTs output a logic '1' (high voltage) for idle state! This signal will go to 0v for the start bit. <br />
<br />
The A signal is the wire that, when in the idle state, is at a slightly higher voltage than the 'B' signal. This difference in voltage measurements is the result of the biasing and termination resistors of the circuit. See [https://en.wikipedia.org/wiki/RS-485#/media/File:Rs485-bias-termination.svg Wikipedia]<br />
<br />
<br />
'''Identifying 'Mark/Idle' and 'Space' '''<br />
<br />
Look at the data bits. The idle condition is always the 'mark' condition. The start bit is always a 'space'. Drawings on the internet are in conflict with each other and cannot be relied upon.<br />
<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ Nominal Terminology<br />
|-<br />
! Our Terminology !! Description !! Terminonlogy !! Data (UART) Representation !! When Idle<br />
|-<br />
| A || Tracking UART value || Non-Inverting || A is high when UART emitting 1, A is low when UART emitting 0 || High<br />
|-<br />
| B || Non-tracking || Inverting || B is low when UART emitting 1, B is high when UART emitting 0 || Low<br />
|}<br />
<br />
<br />
<br />
{| class="wikitable" style="text-align: center;" <br />
|+ Manufacturer's Labeling<br />
|-<br />
! Non-inverting !! Inverting !! Class !! Manufacturer examples !!<br />
|-<br />
| A || B || Nominal || BITS, FieldServer<br />
|-<br />
| + || - || Symbol || BACnet Specification || The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" <br />
|-<br />
| RT+ || RT- || || EnOcean SmartServer IoT<br />
|-<br />
| + || - || Symbol || FT-Click, BASRouter LX, Onicon F-4300<br />
|-<br />
| B+ || A- || This is obviously contrary to everyone else || MBS UBR-01 Mk II<br />
|-<br />
| 485+ || 485- || Symbol || FieldServer<br />
|-<br />
| U+ || U- || || [https://en.wikipedia.org/wiki/RS-485#Waveform_example Wikipedia]<br />
|-<br />
| B || A || || [https://en.wikipedia.org/wiki/RS-485#Signals Wikipedia. See, what a fiasco]<br />
|-<br />
| A+ || B- || || [https://www.waveshare.com/product/iot-communication/wired-comm-converter/usb-to-rs485.htm Waveshare USB to RS-485], AirBox<br />
|-<br />
| A || B || || [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf TI Polarity Conventions]<br />
|-<br />
| ? || ? || || KMC router, A- and B+, true polarity TBC<br />
|}<br />
<br />
The BACnet Specification (135 - 9.2.2) says: The non-inverting input of the<br />
EIA-485 transceiver is designated in this specification as "plus" or "+" and the inverting input as "minus" or "-". It is recommended, but not required, that the black or red insulated wire of the twisted pair be designated as "plus" and the white, clear, or green insulated wire be designated as "minus." <br />
<br />
TI has a very definitive [https://e2e.ti.com/cfs-file/__key/telligent-evolution-components-attachments/13-143-00-00-00-26-49-60/RS485-_2D00_-Polarity-Conventions.pdf document], but one that has to be read carefully in terms of terminology. Read this document with the following table in mind. Note, according to TI (and our opinion), the [https://en.wikipedia.org/wiki/RS-485 Wikipedia article] on bus states is WRONG ! :<br />
<br />
{| class="wikitable" style="text-align: center;"<br />
|+ RS-485 Bus State Terminology<br />
|-<br />
! UART input/output !! A vs B !! Legacy !! RS-485 Bus State !! RS-485 Bus Binary state<br />
|-<br />
| 1 || A > B|| Mark/Idle || On || Logic 0<br />
|-<br />
| 0 || A < B || Space || Off || Logic 1<br />
|}</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BACnet_Standard&diff=13712BACnet Standard2026-02-09T19:05:00Z<p>BACnetEd: </p>
<hr />
<div>The BACnet Standard can be purchased from the ASHRAE Bookstore.<br />
<br />
<br />
The official BACnet Website [https://bacnet.org/ is this]. <br />
<br />
For the official BACnet standard go to this link and search for "BACnet 135"<br />
<br />
For the official BACnet *TEST* standard go to this link and search for "BACnet 135.1"<br />
<br />
<br />
<br />
There is an online read-only version available via [https://www.ashrae.org/technical-resources/standards-and-guidelines/read-only-versions-of-ashrae-standards this link]. Go to this link and search for "135-2024"</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BTL_Procedure&diff=13711BTL Procedure2025-11-29T19:34:46Z<p>BACnetEd: </p>
<hr />
<div>Here is a summary/checklist to get your device through the BTL certification process:<br />
<br />
* Pre-test your device using our BACnet Test Suite<br />
* Contact the 4 labs, ([https://btl.org/device-testing/#provider-section link here]) let them know that you are interested, confirm they can test your IUT (Implementation Under Test)<br />
* Confirm they will test to Protocol Revision 26 (or perhaps higher)<br />
* Confirm they will provide an estimate (quote) based on the "BTL Functionality Checklist" that you will fill in<br />
* Find out when they can start testing, and estimate how long will it take<br />
* Confirm Payment terms<br />
* Ask for any other requirements they may have<br />
* Complete the "BTL Functionality Checklist". The original is in the "BTL Test Package-26" which can be downloaded from the BTL website<br />
* Send this to the candidate lab(s) and get a final estimate of the costs<br />
* Contact BTL themselves and let them know your intent to start testing with the selected Lab, and ask them to initiate procedures for eventual registration. Someone, not sure who, I think BTL, will issue a TCxxxxxx number for tracking purposes.<br />
* Ask BTL for additional guidance<br />
* There will be additional fees for the "Certification" and "Listing". (You probably do want to be "Listed" on the BTL website (link) for marketing purposes (this link is well referenced by users). But you are able to proceed with just the certificate if desired).<br />
* Select a Lab, proceed<br />
* [https://www.bac-test.com/ BITS] can assist you with this process.</div>BACnetEdhttp://bacnetwiki.com/index.php?title=BTL_Procedure&diff=13710BTL Procedure2025-11-29T19:32:17Z<p>BACnetEd: Created page with "Here is a summary/checklist to get your device through the BTL certification process: * Pre-test your device using our BACnet Test Suite * Contact the 4 labs, (link here) let them know that you are interested, confirm they can test your IUT (Implementation Under Test) * Confirm they will test to Protocol Revision 26 (or perhaps higher) * Confirm they will provide an estimate (quote) based on the "BTL Functionality Checklist" that you will fill in * Find out when they ca..."</p>
<hr />
<div>Here is a summary/checklist to get your device through the BTL certification process:<br />
<br />
* Pre-test your device using our BACnet Test Suite<br />
* Contact the 4 labs, (link here) let them know that you are interested, confirm they can test your IUT (Implementation Under Test)<br />
* Confirm they will test to Protocol Revision 26 (or perhaps higher)<br />
* Confirm they will provide an estimate (quote) based on the "BTL Functionality Checklist" that you will fill in<br />
* Find out when they can start testing, and estimate how long will it take<br />
* Confirm Payment terms<br />
* Ask for any other requirements they may have<br />
* Complete the "BTL Functionality Checklist". The original is in the "BTL Test Package-26" which can be downloaded from the BTL website<br />
* Send this to the candidate lab(s) and get a final estimate of the costs<br />
* Contact BTL themselves and let them know your intent to start testing with the selected Lab, and ask them to initiate procedures for eventual registration. Someone, not sure who, I think BTL, will issue a TCxxxxxx number for tracking purposes.<br />
* Ask BTL for additional guidance<br />
* There will be additional fees for the "Certification" and "Listing". (You probably do want to be "Listed" on the BTL website (link) for marketing purposes (this link is well referenced by users). But you are able to proceed with just the certificate if desired).<br />
* Select a Lab, proceed<br />
* BITS can assist you with this process.</div>BACnetEdhttp://bacnetwiki.com/index.php?title=Main_Page&diff=13709Main Page2025-11-29T19:28:05Z<p>BACnetEd: </p>
<hr />
<div><big>'''The new BACnetWiki'''</big><br />
<br />
This is a reboot of the BACnet Wiki for consolidating thoughts and discussions around BACnet. Email me at '''edward@bac-test.com''' if needed<br />
<br />
'''Resources'''<br />
* [[BACnet Product Gallery]] - Equipment, tools, services<br />
* [[BACnet Developer Resources]] - for BACnet Stack programmers<br />
* [[BACnet User Resources]] - for those of us who use BACnet devices<br />
* [[Facilities Manager Resources]] - for those responsible for a site containing hundreds or thousands of BACnet devices<br />
* [[Resources for Beginners]]<br />
* [[Installer Resources]] - help with installing BACnet systems<br />
<!--- * [https://forum.bac-test.com/ BACnet discussion forum] --><br />
* The [[BACnet Standard]]<br />
* [https://www.linkedin.com/groups/13566440/ BACnet Developers Group on LinkedIn]<br />
* [[BACnet Protocol]]<br />
* [[BIBBS - BACnet Interoperability Building Blocks]]<br />
* [[BACnet Services Supported]]<br />
* [[BACnet Addenda 135]]<br />
* [[BACnet Addenda 135.1]]<br />
* [[BACnet BTL Tests to final 135.1 Tracking]]<br />
* [[BACnet Interpretations]]<br />
* [[BTL Procedure | BTL Submittal Process]]<br />
* [[BTL Resources]]<br />
* [[BTL Test Plan]]<br />
* [[BTL Implementation Guideline]]<br />
* Proposed [[Diagnostic Object]]<br />
* [[BACnet Best Practices]]<br />
* [[BACnet Protocol Wish List]]<br />
* [[BACnet MS/TP Best Practices]]<br />
* [[RS-485 Polarity]]<br />
* [[BACnet Organizations]]<br />
* [[Book of Records]]</div>BACnetEdhttp://bacnetwiki.com/index.php?title=DM-R-B_-_Device_Management_-_Restart&diff=13708DM-R-B - Device Management - Restart2025-11-29T12:20:44Z<p>BACnetEd: Created page with "2025-11-29 I have asked this question My reference: oi00192 Does a device *HAVE* to support sending a UCOV on restart? ... (Clause 19.3) "When a device is powered on, when it restarts due to a ReinitializeDevice service (ACTIVATE_CHANGES, COLDSTART or WARMSTART), or when it restarts for some other reason, the device shall transmit an UnconfirmedCOVNotification request. " (B-ASC and lesser devices are not required to support DM-BR-B, nor is DM-R-B listed, but the text..."</p>
<hr />
<div>2025-11-29 I have asked this question<br />
My reference: oi00192<br />
<br />
Does a device *HAVE* to support sending a UCOV on restart? ... (Clause 19.3)<br />
<br />
"When a device is powered on, when it restarts due to a ReinitializeDevice service (ACTIVATE_CHANGES, COLDSTART<br />
or WARMSTART), or when it restarts for some other reason, the device shall transmit an UnconfirmedCOVNotification<br />
request. "<br />
<br />
(B-ASC and lesser devices are not required to support DM-BR-B, nor is DM-R-B listed, but the text above implies otherwise..., and any Network_Port modification, requiring an ACTIVATE_CHANGES will too)<br />
<br />
Very small devices, if forced to do the above, are not going to maintain a writable, and by definition persistable, Restart_Notification_Recipients list, and thus will fall back to a broadcast UCOV, bringing us back to the "very busy network on site power-up" issue that caused the suppression of I-Ams on startups....</div>BACnetEd