Plane: move support for inverted flight to rc-aux-switch

Functional change here; if someone de-configures the rc aux switch in
flight they will remain inverted

ArduPlane/Parameters.cpp

@@ -821,13 +821,6 @@ const AP_Param::Info Plane::var_info[] = {
     GSCALAR(override_safety,      "OVERRIDE_SAFETY",  1),
 #endif
 
-    // @Param: INVERTEDFLT_CH
-    // @DisplayName: Inverted flight channel
-    // @Description: A RC input channel number to enable inverted flight. If this is non-zero then the APM will monitor the corresponding RC input channel and will enable inverted flight when the channel goes above 1750.
-    // @Values: 0:Disabled,1:Channel1,2:Channel2,3:Channel3,4:Channel4,5:Channel5,6:Channel6,7:Channel7,8:Channel8
-    // @User: Standard
-    GSCALAR(inverted_flight_ch,     "INVERTEDFLT_CH", 0),
-
 #if HIL_SUPPORT
     // @Param: HIL_MODE
     // @DisplayName: HIL mode enable

ArduPlane/Parameters.h

@@ -215,7 +215,7 @@ public:
         k_param_pitch_limit_min_cd,
         k_param_airspeed_cruise_cm,
         k_param_RTL_altitude_cm,
-        k_param_inverted_flight_ch,
+        k_param_inverted_flight_ch_unused, // unused
         k_param_min_gndspeed_cm,
         k_param_crosstrack_use_wind, // unused
 
@@ -467,7 +467,6 @@ public:
     AP_Int8 flap_2_percent;
     AP_Int8 flap_2_speed;
     AP_Int8 takeoff_flap_percent;  
-    AP_Int8 inverted_flight_ch;             // 0=disabled, 1-8 is channel for inverted flight trigger
     AP_Int8 stick_mixing;
     AP_Float takeoff_throttle_min_speed;
     AP_Float takeoff_throttle_min_accel;

ArduPlane/RC_Channel.cpp

@@ -33,6 +33,7 @@ void RC_Channel_Plane::init_aux_function(const RC_Channel::aux_func_t ch_option,
     switch(ch_option) {
     // the following functions do not need to be initialised:
     case ARMDISARM:
+    case INVERTED:
         break;
     default:
         RC_Channel::init_aux_function(ch_option, ch_flag);
@@ -58,6 +59,9 @@ void RC_Channel_Plane::do_aux_function(const aux_func_t ch_option, const aux_swi
             break;
         }
         break;
+    case INVERTED:
+        plane.inverted_flight = (ch_flag == HIGH);
+        break;
     default:
         RC_Channel::do_aux_function(ch_option, ch_flag);
         break;

ArduPlane/config.h

@@ -292,10 +292,6 @@
  # define USE_CURRENT_ALT FALSE
 #endif
 
-#ifndef INVERTED_FLIGHT_PWM
- # define INVERTED_FLIGHT_PWM 1750
-#endif
-
 #ifndef PX4IO_OVERRIDE_PWM
  # define PX4IO_OVERRIDE_PWM 1750
 #endif

ArduPlane/control_modes.cpp

@@ -52,12 +52,6 @@ void Plane::read_control_switch()
 
     switch_debouncer = false;
 
-    if (g.inverted_flight_ch != 0) {
-        // if the user has configured an inverted flight channel, then
-        // fly upside down when that channel goes above INVERTED_FLIGHT_PWM
-        inverted_flight = (control_mode != MANUAL && RC_Channels::get_radio_in(g.inverted_flight_ch-1) > INVERTED_FLIGHT_PWM);
-    }
-
 #if PARACHUTE == ENABLED
     if (g.parachute_channel > 0) {
         if (RC_Channels::get_radio_in(g.parachute_channel-1) >= 1700) {
@@ -151,8 +145,11 @@ void Plane::autotune_enable(bool enable)
  */
 bool Plane::fly_inverted(void)
 {
-    if (g.inverted_flight_ch != 0 && inverted_flight) {
-        // controlled with INVERTED_FLIGHT_CH
+    if (control_mode == MANUAL) {
+        return false;
+    }
+    if (inverted_flight) {
+        // controlled with aux switch
         return true;
     }
     if (control_mode == AUTO && auto_state.inverted_flight) {