Copter: add WP_YAW_BEHAVE parameter

Allows user to control whether nose points towards next waypoint and/or
home when RTLing.
Replaces YAW_OVR_BEHAVE which had a very similar purpose.  Almost nobody
ever knew about or used this parameter.

ArduCopter/Parameters.h

@@ -78,7 +78,7 @@ public:
         k_param_crosstrack_min_distance,	// deprecated - remove with next eeprom number change
         k_param_rssi_pin,
         k_param_throttle_accel_enabled,
-        k_param_yaw_override_behaviour,
+        k_param_wp_yaw_behavior,
         k_param_acro_trainer_enabled,
         k_param_pilot_velocity_z_max,   // 28
 
@@ -282,7 +282,7 @@ public:
     AP_Int8         battery_curr_pin;
     AP_Int8         rssi_pin;
     AP_Int8         throttle_accel_enabled;      // enable/disable accel based throttle controller
-    AP_Int8         yaw_override_behaviour;     // controls when autopilot takes back normal control of yaw after pilot overrides
+    AP_Int8         wp_yaw_behavior;            // controls how the autopilot controls yaw during missions
 
     // Waypoints
     //

ArduCopter/Parameters.pde

@@ -182,12 +182,12 @@ const AP_Param::Info var_info[] PROGMEM = {
     // @User: Standard
     GSCALAR(throttle_accel_enabled,  "THR_ACC_ENABLE",   1),
 
-    // @Param: YAW_OVR_BEHAVE
-    // @DisplayName: Yaw override behaviour
-    // @Description: Controls when autopilot takes back normal control of yaw after pilot overrides
-    // @Values: 0:At Next WP, 1:On Mission Restart
+    // @Param: WP_YAW_BEHAVIOR
+    // @DisplayName: Yaw behaviour during missions
+    // @Description: Determines how the autopilot controls the yaw during missions and RTL
+    // @Values: 0:Never change yaw, 1:Face next waypoint, 2:Face next waypoint except RTL
     // @User: Advanced
-    GSCALAR(yaw_override_behaviour,  "YAW_OVR_BEHAVE",   YAW_OVERRIDE_BEHAVIOUR_AT_NEXT_WAYPOINT),
+    GSCALAR(wp_yaw_behavior,  "WP_YAW_BEHAVIOR",    WP_YAW_BEHAVIOR_LOOK_AT_NEXT_WP),
 
     // @Param: WP_TOTAL
     // @DisplayName: Waypoint Total

ArduCopter/commands_logic.pde

@@ -279,7 +279,7 @@ static void do_nav_wp()
     loiter_time_max = command_nav_queue.p1;
 
     // reset control of yaw to default
-    if( g.yaw_override_behaviour == YAW_OVERRIDE_BEHAVIOUR_AT_NEXT_WAYPOINT ) {
+    if( g.wp_yaw_behavior == WP_YAW_BEHAVIOR_LOOK_AT_NEXT_WP || g.wp_yaw_behavior == WP_YAW_BEHAVIOR_LOOK_AT_NEXT_WP_EXCEPT_RTL) {
         set_yaw_mode(AUTO_YAW);
     }
 }
@@ -516,8 +516,9 @@ static bool verify_RTL()
                 rtl_state = RTL_STATE_INITIAL_CLIMB;
             }else{
                 // point nose towards home
-                // To-Do: make this user configurable whether RTL points towards home or not
-                set_yaw_mode(RTL_YAW);
+                if(g.wp_yaw_behavior == WP_YAW_BEHAVIOR_LOOK_AT_NEXT_WP) {
+                    set_yaw_mode(RTL_YAW);
+                }
 
                 // Set wp navigation target to above home
                 wp_nav.set_destination(Vector3f(0,0,get_RTL_alt()));

ArduCopter/defines.h

@@ -187,9 +187,10 @@
 #define NAV_WP          3
 #define NAV_WP_INAV     5
 
-// Yaw override behaviours - used for setting yaw_override_behaviour
-#define YAW_OVERRIDE_BEHAVIOUR_AT_NEXT_WAYPOINT     0   // auto pilot takes back yaw control at next waypoint
-#define YAW_OVERRIDE_BEHAVIOUR_AT_MISSION_RESTART   1   // auto pilot tkaes back control only when mission is restarted
+// Yaw behaviours during missions - possible values for WP_YAW_BEHAVIOR parameter
+#define WP_YAW_BEHAVIOR_NONE                          0   // auto pilot will never control yaw during missions or rtl (except for DO_CONDITIONAL_YAW command received)
+#define WP_YAW_BEHAVIOR_LOOK_AT_NEXT_WP               1   // auto pilot will face next waypoint or home during rtl
+#define WP_YAW_BEHAVIOR_LOOK_AT_NEXT_WP_EXCEPT_RTL    2   // auto pilot will face next waypoint except when doing RTL at which time it will stay in it's last 
 
 // TOY mixing options
 #define TOY_LOOKUP_TABLE 0