Implement BLE OTA

web/app.js

@@ -1015,3 +1015,35 @@ if (!navigator.bluetooth) {
 } else {
   log('Web Bluetooth ready. Click CONNECT to pair your IMU Mouse.','info');
 }
+
+// ─────────────────────────────────────────────────────────────────────────────
+//  OTA firmware update
+//
+//  The OTAFIX bootloader uses Nordic Legacy DFU (service 00001530-...) which is
+//  blocklisted in Chrome's Web Bluetooth implementation.  Browser-side upload is
+//  therefore not possible without special flags or a native app wrapper.
+//
+//  What the UI does instead:
+//    • "Enter DFU Mode" sends command 0x02 via BLE → device reboots as XIAO_DFU
+//    • User then uploads firmware_dfu.zip via nRF Connect (mobile or desktop)
+// ─────────────────────────────────────────────────────────────────────────────
+
+function otaLog(msg, type = 'info') {
+  log('[OTA] ' + msg, type);
+  const el = document.getElementById('otaStatus');
+  if (el) { el.textContent = msg; el.className = 'ota-status' + (type !== 'info' ? ' ota-' + type : ''); }
+}
+
+// Send command 0x02 → firmware reboots into XIAO_DFU bootloader mode.
+// User then uploads firmware_dfu.zip via nRF Connect.
+async function sendOTATrigger() {
+  if (!chars.command) { otaLog('Not connected', 'err'); return; }
+  document.getElementById('btnOTA').disabled = true;
+  try {
+    await chars.command.writeValueWithResponse(new Uint8Array([0x02]));
+    otaLog('Device rebooting into DFU mode — connect to XIAO_DFU in nRF Connect', 'ok');
+  } catch (e) {
+    otaLog('Failed: ' + e.message, 'err');
+    document.getElementById('btnOTA').disabled = false;
+  }
+}