# 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.