Plane: Modified last_valid_rc_ms AFS failsafe input to work when standard failsafe is on

Ran into a bug on our physical plane where failsafe.last_valid_rc_ms was not recognizing that the transmitter had failed. This is likely due to how the standard failsafe works in receiving lower-than-possible throttle values. So in order to account for this, I added a new variable to the failsafe, AFS_last_valid_rc_ms, and I update it only if the ch3_failsafe (the throttle failsafe) is not on. If the throttle failsafe is on, that means that the plane has indeed lost transmitter input, so the AFS needs to recognize that.

ArduPlane/ArduPlane.cpp

@@ -294,7 +294,7 @@ void Plane::obc_fs_check(void)
 {
 #if OBC_FAILSAFE == ENABLED
     // perform OBC failsafe checks
-    obc.check(OBC_MODE(control_mode), failsafe.last_heartbeat_ms, geofence_breached(), failsafe.last_valid_rc_ms);
+    obc.check(OBC_MODE(control_mode), failsafe.last_heartbeat_ms, geofence_breached(), failsafe.AFS_last_valid_rc_ms);
 #endif
 }
 

ArduPlane/GCS_Mavlink.cpp

@@ -1848,6 +1848,7 @@ void GCS_MAVLINK::handleMessage(mavlink_message_t* msg)
 
         if (hal.rcin->set_overrides(v, 8)) {
             plane.failsafe.last_valid_rc_ms = AP_HAL::millis();
+            plane.failsafe.AFS_last_valid_rc_ms =  plane.failsafe.last_valid_rc_ms;
         }
 
         // a RC override message is consiered to be a 'heartbeat' from

ArduPlane/Plane.h

@@ -345,6 +345,10 @@ private:
         uint32_t ch3_timer_ms;
         
         uint32_t last_valid_rc_ms;
+
+        //keeps track of the last valid rc as it relates to the AFS system
+        //Does not count rc inputs as valid if the standard failsafe is on
+        uint32_t AFS_last_valid_rc_ms;
     } failsafe;
 
     // A counter used to count down valid gps fixes to allow the gps estimate to settle

ArduPlane/radio.cpp

@@ -162,6 +162,11 @@ void Plane::read_radio()
         return;
     }
 
+    if(!failsafe.ch3_failsafe)
+    {
+        failsafe.AFS_last_valid_rc_ms = millis();
+    }
+
     failsafe.last_valid_rc_ms = millis();
 
     elevon.ch1_temp = channel_roll->read();