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