xterra-overland-dashboard/docs/uart.md

UART Communication Plan

Overview

The first hardware version will use UART over CAT5 between the Pico dashboard and the ESP32 controller.

UART is simpler than RS-485 and should be reliable for the short cable run inside the Xterra.

RS-485 remains a future fallback if testing reveals communication issues.

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

Future Options:

• 57600
• 230400

Message Format

Newline-delimited JSON

Request: {"type":"status_request"}

Response: {"type":"status_response"}

Failure Handling

If communication is lost:

• Dashboard shows warning
• Last known values remain visible
• Relay commands fail safely
• WiFi backup may be attempted

Advantages

• Fewer parts
• Easier debugging
• Easier wiring
• No transceivers
• No direction control
• Works well for short runs

Future RS-485 Option

If vehicle electrical noise causes issues, the transport layer can be switched to RS-485 without changing application logic.