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UART Communication Plan
Overview
The first hardware version will use plain UART over CAT5 between the Pico dashboard and the ESP32 cargo controller.
UART is simpler than RS-485 and should be reliable enough for the short cable run inside the Xterra.
RS-485 remains a fallback if UART proves unreliable.
Architecture
Pico Dashboard ↓ UART over CAT5 ↓ ESP32 Controller
Backup: WiFi HTTP API
Fallback: RS-485 over CAT5
UART Wiring
Pico TX -> ESP32 RX Pico RX <- ESP32 TX Ground <-> Ground
Planned Baud Rate
Initial: 115200 baud
Future testing:
- 57600 baud if noise becomes an issue
- 230400 baud if higher update rates are needed
Message Format
Messages will use newline-delimited JSON.
Example request:
{"type":"status_request"}
Example response:
{"type":"status_response","data":{"battery":{"soc":82}}}
Each message ends with a newline character.
Failure Handling
If no valid response is received within the timeout:
- Dashboard shows communication warning
- Last known values remain visible
- Relay commands fail safely
- WiFi backup may be attempted if enabled
Why UART First
Advantages:
- Fewer parts
- Easier wiring
- Easier debugging
- No direction-control pin
- No transceiver modules required
- Works well over short distances
Why RS-485 Is Still Available
RS-485 may be used later if UART has issues caused by:
- Alternator noise
- Relay switching noise
- Fridge compressor noise
- Inverter noise
- Long cable run
- Ground noise
The software should keep a transport abstraction so UART and RS-485 can be swapped without changing the application protocol.