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esp32-c_its-companion/docs/uart-protocol.md
Jannik Beyerstedt 29a5d86e43 docs: Add BLE and UART protocol specification
2026-07-22 15:14:15 +02:00

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UART Protocol

If enabled using the TODO feature flag, all received messages are transmitted on UART using the protocol described in this document. The serial communication can also be used to send V2X data.

Message Format

The UART communication is using a custom framing protocol to encapsulate binary messages. The payload is:

  • a SerialOutputMsg for transmissions from the ESP to the host or
  • a SerialInputMsg for transmissions from the host to the ESP

in binary Proto serialization according to the c_its-messages.proto definition.

Each transmission:

  • starts with a Start of Frame (SOF) sequence: 0x56, 0x32, 0x58, 0x2B ("V2X+")
  • followed by a 16-bit big-endian length field
  • followed by the payload
  • followed by an End of Frame (EOF) sequence 0x0d, 0x0a