Support cmd over serial

source/main.cpp

@@ -274,6 +274,13 @@ void loop() {
     }
   #endif
 
+  // Serial commands: 'c' = calibrate, 'r' = factory reset
+  while (Serial.available()) {
+    char cmd = Serial.read();
+    if (cmd == 'c') { Serial.println("[SERIAL] Calibrate"); pendingCal   = true; }
+    if (cmd == 'r') { Serial.println("[SERIAL] Reset");     pendingReset = true; }
+  }
+
   if (pendingCal)   { pendingCal   = false; calibrateGyroBias(); }
   if (pendingReset) { pendingReset = false; factoryReset(); }