RS-485 Polarity
RS-485 comprises two signals, one that 'tracks' the logic levels (high voltage == 1, low voltage == 0). The other signal does the opposite. The labeling of these two signals has been polluted by chip and box vendors, which leads to a lot of confusion. This article attempts to resolve the status without adding to the confusion
Our terminology:
| Our Terminology | Description | Logic levels | Data Representation |
|---|---|---|---|
| T+ | Tracking | High voltage (typically +5 or +3.3) | 1 |
| T- | Non-tracking | Low voltage (close to 0v) | 0 |
Labeling found in the field
| Comment | Tracking | Non-tracking | Class | Manufacturer examples |
|---|---|---|---|---|
| Our terminology | T+ | T- | Nominal | BITS |
| + | - | Symbol | FT-Click, BASRouterLX | |
| B+ | A- | MBS UBR-01 MkII | ||
| U+ | U- | Wikipedia | ||
| Example | Example | Example | Example | |
| Example | Example | Example | Example | |
| Example | Example | Example | Example | |
| Example | Example | Example | Example | |
| Example | Example | Example | Example | |
| Example | Example | Example | Example |