Copter: report RC receiver health to GCS

ArduCopter/ArduCopter.pde

@@ -395,6 +395,8 @@ static union {
         uint8_t yaw_stopped         : 1; // 16      // Used to manage the Yaw hold capabilities
 
         uint8_t disable_stab_rate_limit : 1; // 17  // disables limits rate request from the stability controller
+
+        uint8_t rc_receiver_present : 1; // 18  // true if we have an rc receiver present (i.e. if we've ever received an update
     };
     uint32_t value;
 } ap;

ArduCopter/GCS_Mavlink.pde

@@ -156,6 +156,9 @@ static NOINLINE void send_extended_status1(mavlink_channel_t chan, uint16_t pack
         control_sensors_present |= MAV_SYS_STATUS_SENSOR_OPTICAL_FLOW;
     }
 #endif
+    if (ap.rc_receiver_present) {
+        control_sensors_present |= MAV_SYS_STATUS_SENSOR_RC_RECEIVER;
+    }
 
     // all present sensors enabled by default except altitude and position control which we will set individually
     control_sensors_enabled = control_sensors_present & (~MAV_SYS_STATUS_SENSOR_Z_ALTITUDE_CONTROL & ~MAV_SYS_STATUS_SENSOR_XY_POSITION_CONTROL);
@@ -180,14 +183,17 @@ static NOINLINE void send_extended_status1(mavlink_channel_t chan, uint16_t pack
         break;
     }
 
-    // default to all healthy except compass and gps which we set individually
-    control_sensors_health = control_sensors_present & (~MAV_SYS_STATUS_SENSOR_3D_MAG & ~MAV_SYS_STATUS_SENSOR_GPS);
+    // default to all healthy except compass, gps and receiver which we set individually
+    control_sensors_health = control_sensors_present & (~MAV_SYS_STATUS_SENSOR_3D_MAG & ~MAV_SYS_STATUS_SENSOR_GPS & ~MAV_SYS_STATUS_SENSOR_RC_RECEIVER);
     if (g.compass_enabled && compass.healthy && ahrs.use_compass()) {
         control_sensors_health |= MAV_SYS_STATUS_SENSOR_3D_MAG;
     }
     if (g_gps != NULL && g_gps->status() > GPS::NO_GPS && !gps_glitch.glitching()) {
         control_sensors_health |= MAV_SYS_STATUS_SENSOR_GPS;
     }
+    if (ap.rc_receiver_present && !failsafe.radio) {
+        control_sensors_health |= MAV_SYS_STATUS_SENSOR_RC_RECEIVER;
+    }
 
     int16_t battery_current = -1;
     int8_t battery_remaining = -1;

ArduCopter/radio.pde

@@ -130,6 +130,11 @@ static void read_radio()
         g.rc_6.set_pwm(periods[5]);
         g.rc_7.set_pwm(periods[6]);
         g.rc_8.set_pwm(periods[7]);
+
+        // flag we must have an rc receiver attached
+        if (!failsafe.rc_override_active) {
+            ap.rc_receiver_present = true;
+        }
     }else{
         uint32_t elapsed = millis() - last_update;
         // turn on throttle failsafe if no update from ppm encoder for 2 seconds