firmware: add OLED status panel to camera node (C6)

Bring up the 1.3" SH1106 128x64 I2C OLED on the XIAO ESP32-C6
(D4/SDA, D5/SCL @ 0x3C) per the Notion wiring diagram.

- add U8g2 dependency to the seeed_xiao_esp32c6 env
- I2C bus scan at boot (logs responders to serial)
- boot splash + live status screen: camera id, IDLE/REC + session
  timer, battery (raw until calibrated) + video-remaining, hub link
  state (MQTT/wifi/offline), and camera reachability
- refresh runs at the top of loop() so the panel stays live even
  when WiFi/MQTT are down

Verified on hardware: I2C scan finds 0x3C, U8g2 begin ok, panel
shows clean readable text.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

firmware/platformio.ini

@@ -65,7 +65,9 @@ platform = https://github.com/pioarduino/platform-espressif32/releases/download/
 board = seeed_xiao_esp32c6
 framework = arduino
 monitor_speed = 115200
-lib_deps = ${common.lib_deps}
+lib_deps =
+    ${common.lib_deps}
+    olikraus/U8g2 @ ^2.35
 build_flags = ${common.build_flags}
     -D CONFIG_ARDUINO_LOOP_STACK_SIZE=8192
     -D ARDUINO_USB_MODE=1

firmware/src/esp32-mqtt-bridge.cpp

@@ -31,6 +31,8 @@
 #include <PubSubClient.h>
 #include <ArduinoJson.h>
 #include <SPIFFS.h>
+#include <Wire.h>
+#include <U8g2lib.h>
 
 // ────────────────────────────────────────────
 // Configuration (SPIFFS)
@@ -91,9 +93,58 @@ bool saveConfig() {
 #define UART_TX_PIN  D6
 
 // Camera-online indicator → green channel of the RGB STAT LED.
-// (Full RGB/OLED status-panel bring-up is not implemented yet.)
 #define STAT_LED_PIN D1
 
+// ────────────────────────────────────────────
+// Status OLED — 1.3" I2C panel on D4(SDA)/D5(SCL)
+// ────────────────────────────────────────────
+// 1.3" 128x64 modules are SH1106. If the image is shifted ~2px or
+// wrapped, the panel is an SSD1306 — swap the constructor below to
+// U8G2_SSD1306_128X64_NONAME_F_HW_I2C.
+#define OLED_SDA_PIN  D4
+#define OLED_SCL_PIN  D5
+#define OLED_I2C_ADDR 0x3C
+
+U8G2_SH1106_128X64_NONAME_F_HW_I2C oled(U8G2_R0, U8X8_PIN_NONE);
+bool oledReady = false;
+
+// Last-known camera status, mirrored for the display.
+int  dispBatteryRaw  = 0;
+bool dispRecording   = false;
+int  dispVideoRemain = 0;          // seconds
+unsigned long recStartMs = 0;      // 0 = not recording
+
+// Walk the bus and log every responder — confirms the OLED address
+// (and wiring) independent of the display driver.
+void i2cScan() {
+  Serial.println("[I2C] Scanning...");
+  byte found = 0;
+  for (byte a = 1; a < 127; a++) {
+    Wire.beginTransmission(a);
+    if (Wire.endTransmission() == 0) {
+      Serial.printf("[I2C]   device @ 0x%02X\n", a);
+      found++;
+    }
+  }
+  if (!found) Serial.println("[I2C]   none found — check wiring/power");
+}
+
+void displayInit() {
+  Wire.begin(OLED_SDA_PIN, OLED_SCL_PIN);
+  i2cScan();
+  oled.setI2CAddress(OLED_I2C_ADDR << 1);
+  oledReady = oled.begin();
+  Serial.printf("[OLED] begin %s\n", oledReady ? "ok" : "FAILED");
+  if (!oledReady) return;
+  oled.clearBuffer();
+  oled.setFont(u8g2_font_7x14B_tr);
+  oled.drawStr(0, 14, "RemoteRig");
+  oled.setFont(u8g2_font_6x10_tr);
+  oled.drawStr(0, 32, "Camera node");
+  oled.drawStr(0, 46, "booting...");
+  oled.sendBuffer();
+}
+
 void sendCmdToESP8266(const String& command) {
   JsonDocument doc;
   doc["type"]    = "cmd";
@@ -201,6 +252,48 @@ bool connectMQTT() {
   return true;
 }
 
+// ────────────────────────────────────────────
+// Status screen
+// ────────────────────────────────────────────
+
+void renderStatus() {
+  if (!oledReady) return;
+  oled.clearBuffer();
+
+  // Camera id (top, bold)
+  oled.setFont(u8g2_font_7x14B_tr);
+  String id = cfg.camera_id.length() ? cfg.camera_id : clientID();
+  oled.drawStr(0, 13, id.c_str());
+
+  oled.setFont(u8g2_font_6x10_tr);
+  char line[24];
+
+  // REC state + session timer
+  if (dispRecording) {
+    unsigned long s = recStartMs ? (millis() - recStartMs) / 1000 : 0;
+    oled.drawBox(0, 19, 6, 6);                       // filled square = REC
+    snprintf(line, sizeof(line), "REC  %02lu:%02lu", s / 60, s % 60);
+    oled.drawStr(10, 26, line);
+  } else {
+    oled.drawStr(0, 26, "IDLE");
+  }
+
+  // Battery (raw until calibrated) + video remaining (minutes)
+  snprintf(line, sizeof(line), "BAT %d  VID %dm", dispBatteryRaw, dispVideoRemain / 60);
+  oled.drawStr(0, 38, line);
+
+  // Uplink to the hub
+  const char* link = mqtt.connected()              ? "LINK: MQTT ok"
+                   : WiFi.status() == WL_CONNECTED  ? "LINK: wifi only"
+                                                    : "LINK: offline";
+  oled.drawStr(0, 50, link);
+
+  // Camera reachability
+  oled.drawStr(0, 62, cameraOnline ? "CAM: online" : "CAM: --");
+
+  oled.sendBuffer();
+}
+
 // ────────────────────────────────────────────
 // Setup
 // ────────────────────────────────────────────
@@ -214,6 +307,8 @@ void setup() {
   pinMode(STAT_LED_PIN, OUTPUT); // RGB STAT LED — green = camera online
   digitalWrite(STAT_LED_PIN, LOW);
 
+  displayInit(); // I2C scan + OLED splash
+
   loadConfig();
 
   // UART to ESP-01S
@@ -251,6 +346,10 @@ void loop() {
   static unsigned long lastBeat = 0, lastRecon = 0;
   static int reconDelay = 1;
 
+  // ── OLED refresh (always — keep the panel live even when offline) ──
+  static unsigned long lastDisp = 0;
+  if (now - lastDisp > 500) { lastDisp = now; renderStatus(); }
+
   // ── Wi-Fi watchdog ──
   if (WiFi.status() != WL_CONNECTED) {
     if (now - lastRecon > 5000) { lastRecon = now; WiFi.reconnect(); }
@@ -288,6 +387,14 @@ void loop() {
         digitalWrite(STAT_LED_PIN, online ? HIGH : LOW);
       }
 
+      // Mirror status onto the OLED fields
+      dispBatteryRaw  = doc["battery_raw"] | 0;
+      dispVideoRemain = doc["video_remaining_sec"] | 0;
+      bool rec = doc["recording"] | false;
+      if (rec && !dispRecording) recStartMs = millis();
+      if (!rec)                  recStartMs = 0;
+      dispRecording = rec;
+
       if (cfg.camera_id.length() > 0) {
         // Build the MQTT status payload per contract
         JsonDocument mqttDoc;