RC & Communications

WiFi Access Point

The ESP32 starts as a WiFi AP at power-on — in both modes. No router, no internet.

SSID:     RobotAP
Password: enviro123
Robot IP: 192.168.4.1

HTTP Endpoints

Method Endpoint Use
GET / RC page (served from flash — PROGMEM, no SPIFFS upload needed)
POST /rc All commands (JSON body)
GET /data Full run JSON (live; falls back to saved results.json after reboot)

There is no WebSocket and no UDP — plain HTTP is fast enough at D-pad cadence and far simpler to debug.

Command Protocol (POST /rc)

{ "cmd": "FWD" }                          // drive; optional "speed": 0-255
{ "cmd": "BWD" }
{ "cmd": "LEFT" }
{ "cmd": "RIGHT" }
{ "cmd": "STOP" }
{ "cmd": "SAMPLE_WATER", "sector": 2 }    // arm 0° → read → 90°; returns {"ntu": 42.3}
{ "cmd": "SAMPLE_SOIL",  "sector": 2 }    // arm 180° → read → 90°; returns {"pct": 68.5}
{ "cmd": "END_RUN" }                      // finalise + save results.json to SPIFFS
  • sector (1–4) is chosen by the operator on the RC page — this is how samples get accurate sector + terrain labels.
  • Every sample is also printed to serial with units (rulebook-approved output).
  • Drive commands accept an optional speed; default is DRIVE_SPEED from config.

RC Page Interface (192.168.4.1)

Single self-contained HTML page compiled into the firmware (rc_page.h, generated from arduino/rc_page/index.html). No CDN, no external requests.

Element Function
D-pad (hold-to-drive) FWD / BWD / LEFT / RIGHT; STOP centre; releases auto-stop
Sector selector S1–S4 Tags the next sample with the sector the robot is in
💧 Sample Water Deploys arm A, logs NTU, shows reading in the log
🌱 Sample Soil Deploys arm B, logs %, shows reading
🏁 End Run Finalises and persists results.json
Status + log Connection state; last 40 events with timestamps

Editing the page: change arduino/rc_page/index.html, then regenerate the header (command in PLAN.md Phase 2), then re-flash.

Data Retrieval After a Run

  1. Stay connected to RobotAP.
  2. GET 192.168.4.1/data → save JSON (works in both modes; survives reboot via SPIFFS fallback).
  3. Back up to two devices.
  4. Drag-drop into the visualiser for the judges.
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