Reverse engineering effort for the UART protocol used between Focan E-Scooter/-Bike displays (GZ3 is the actual test subject) and motor controllers.
The pinout of the connectors can be acquired from the DUs user manual and here are some additional details I deduced with the help of a multimeter and an oscilloscope:
| Pin # | Wire color | Function | Driven by | note |
|---|---|---|---|---|
| 1 | red | battery voltage | MCU | DU draws about 11 mA when MCU is disconnected and 40 mA during normal operation (without lights). |
| 2 | blue | controller power | DU | This supplies power to the MCU including lights. MCU without lights draws about 29 mA during normal operation. |
| 3 | black | ground | common | Swapping this wire with #2 kills the DU. Ask me how I know. |
| 4 | green | UART RX | MCU to 0~3.32 V | |
| 5 | yellow | UART TX | DU to 0~3.48 V | MCU connects 5k6 pullup from 5 V when controller power is supplied by DU |
The protocol analysis and documentation can be found in ./protocolAnalysis/README.md.