Copter: added FLTMODE_CH parameter

this allows for the flight mode to be on any RC channel, or no channel
at all to disable RC flight modes

ArduCopter/Parameters.cpp

@@ -336,6 +336,13 @@ const AP_Param::Info Copter::var_info[] = {
     // @User: Standard
     GSCALAR(flight_mode6, "FLTMODE6",               FLIGHT_MODE_6),
 
+    // @Param: FLTMODE_CH
+    // @DisplayName: Flightmode channel
+    // @Description: RC Channel to use for flight mode control
+    // @Values: 0:Disabled,5:Channel5,6:Channel6,7:Channel7,8:Channel8
+    // @User: Advanced
+    GSCALAR(flight_mode_chan, "FLTMODE_CH",         CH_MODE_DEFAULT),
+
     // @Param: SIMPLE
     // @DisplayName: Simple mode bitmask
     // @Description: Bitmask which holds which flight modes use simple heading mode (eg bit 0 = 1 means Flight Mode 0 uses simple mode)

ArduCopter/Parameters.h

@@ -313,6 +313,7 @@ public:
         k_param_flight_mode5,
         k_param_flight_mode6,
         k_param_simple_modes,
+        k_param_flight_mode_chan,
 
         //
         // 210: Waypoint data
@@ -432,6 +433,7 @@ public:
     AP_Int8         flight_mode5;
     AP_Int8         flight_mode6;
     AP_Int8         simple_modes;
+    AP_Int8         flight_mode_chan;
 
     // Misc
     //

ArduCopter/config.h

@@ -586,3 +586,7 @@
 #ifndef ADVANCED_FAILSAFE
 # define ADVANCED_FAILSAFE DISABLED
 #endif
+
+#ifndef CH_MODE_DEFAULT
+#define CH_MODE_DEFAULT CH_5
+#endif

ArduCopter/switches.cpp

@@ -15,16 +15,21 @@ struct {
 
 void Copter::read_control_switch()
 {
+    if (g.flight_mode_chan <= 0) {
+        // no flight mode channel
+        return;
+    }
+    
     uint32_t tnow_ms = millis();
 
     // calculate position of flight mode switch
     int8_t switch_position;
-    uint16_t rc5_in = RC_Channels::rc_channel(CH_5)->get_radio_in();
-    if      (rc5_in < 1231) switch_position = 0;
-    else if (rc5_in < 1361) switch_position = 1;
-    else if (rc5_in < 1491) switch_position = 2;
-    else if (rc5_in < 1621) switch_position = 3;
-    else if (rc5_in < 1750) switch_position = 4;
+    uint16_t mode_in = RC_Channels::rc_channel(g.flight_mode_chan-1)->get_radio_in();
+    if      (mode_in < 1231) switch_position = 0;
+    else if (mode_in < 1361) switch_position = 1;
+    else if (mode_in < 1491) switch_position = 2;
+    else if (mode_in < 1621) switch_position = 3;
+    else if (mode_in < 1750) switch_position = 4;
     else switch_position = 5;
 
     // store time that switch last moved