Plane: reset last heartbeat time on startup completion

this gives more time for the GCS to send its first heartbeat

ArduPlane/ArduPlane.pde

@@ -301,8 +301,6 @@ static bool ch3_failsafe;
 // A timer used to help recovery from unusual attitudes.  If we enter an unusual attitude
 // while in autonomous flight this variable is used  to hold roll at 0 for a recovery period
 static uint8_t crash_timer;
-// A timer used to track how long since we have received the last GCS heartbeat or rc override message
-static uint32_t rc_override_fs_timer = 0;
 
 // the time when the last HEARTBEAT message arrived from a GCS
 static uint32_t last_heartbeat_ms;

ArduPlane/GCS_Mavlink.pde

@@ -1775,15 +1775,18 @@ mission_failed:
 
         hal.rcin->set_overrides(v, 8);
 
-        rc_override_fs_timer = millis();
+        // a RC override message is consiered to be a 'heartbeat' from
+        // the ground station for failsafe purposes
+        last_heartbeat_ms = millis();
         break;
     }
 
     case MAVLINK_MSG_ID_HEARTBEAT:
     {
-        // We keep track of the last time we received a heartbeat from our GCS for failsafe purposes
-        if(msg->sysid != g.sysid_my_gcs) break;
-        last_heartbeat_ms = rc_override_fs_timer = millis();
+        // We keep track of the last time we received a heartbeat from
+        // our GCS for failsafe purposes
+        if (msg->sysid != g.sysid_my_gcs) break;
+        last_heartbeat_ms = millis();
         pmTest1++;
         break;
     }

ArduPlane/radio.pde

@@ -134,7 +134,7 @@ static void control_failsafe(uint16_t pwm)
 
     // Check for failsafe condition based on loss of GCS control
     if (rc_override_active) {
-        if(millis() - rc_override_fs_timer > FAILSAFE_SHORT_TIME) {
+        if (millis() - last_heartbeat_ms > FAILSAFE_SHORT_TIME) {
             ch3_failsafe = true;
         } else {
             ch3_failsafe = false;

ArduPlane/system.pde

@@ -304,6 +304,10 @@ static void startup_ground(void)
     // -----------------------
     demo_servos(3);
 
+    // reset last heartbeat time, so we don't trigger failsafe on slow
+    // startup
+    last_heartbeat_ms = millis();
+
     // we don't want writes to the serial port to cause us to pause
     // mid-flight, so set the serial ports non-blocking once we are
     // ready to fly
@@ -371,23 +375,31 @@ static void set_mode(enum FlightMode mode)
 
 static void check_long_failsafe()
 {
+    uint32_t tnow = millis();
     // only act on changes
     // -------------------
     if(failsafe != FAILSAFE_LONG  && failsafe != FAILSAFE_GCS) {
-        if(rc_override_active && millis() - rc_override_fs_timer > FAILSAFE_LONG_TIME) {
+        if (rc_override_active && tnow - last_heartbeat_ms > FAILSAFE_LONG_TIME) {
             failsafe_long_on_event(FAILSAFE_LONG);
         }
-        if(!rc_override_active && failsafe == FAILSAFE_SHORT && millis() - ch3_failsafe_timer > FAILSAFE_LONG_TIME) {
+        if(!rc_override_active && failsafe == FAILSAFE_SHORT && 
+           (tnow - ch3_failsafe_timer) > FAILSAFE_LONG_TIME) {
             failsafe_long_on_event(FAILSAFE_LONG);
         }
-        if(g.gcs_heartbeat_fs_enabled && millis() - rc_override_fs_timer > FAILSAFE_LONG_TIME) {
+        if (g.gcs_heartbeat_fs_enabled && 
+            (tnow - last_heartbeat_ms) > FAILSAFE_LONG_TIME) {
             failsafe_long_on_event(FAILSAFE_GCS);
         }
     } else {
         // We do not change state but allow for user to change mode
-        if(failsafe == FAILSAFE_GCS && millis() - rc_override_fs_timer < FAILSAFE_SHORT_TIME) failsafe = FAILSAFE_NONE;
-        if(failsafe == FAILSAFE_LONG && rc_override_active && millis() - rc_override_fs_timer < FAILSAFE_SHORT_TIME) failsafe = FAILSAFE_NONE;
-        if(failsafe == FAILSAFE_LONG && !rc_override_active && !ch3_failsafe) failsafe = FAILSAFE_NONE;
+        if (failsafe == FAILSAFE_GCS && 
+            (tnow - last_heartbeat_ms) < FAILSAFE_SHORT_TIME) 
+            failsafe = FAILSAFE_NONE;
+        if (failsafe == FAILSAFE_LONG && rc_override_active && 
+            (tnow - last_heartbeat_ms) < FAILSAFE_SHORT_TIME) 
+            failsafe = FAILSAFE_NONE;
+        if (failsafe == FAILSAFE_LONG && !rc_override_active && !ch3_failsafe) 
+            failsafe = FAILSAFE_NONE;
     }
 }