Copter: Auto Yaw variable names and comments

ArduCopter/autoyaw.cpp

@@ -97,18 +97,14 @@ void Mode::AutoYaw::set_mode(autopilot_yaw_mode yaw_mode)
 // set_fixed_yaw - sets the yaw look at heading for auto mode
 void Mode::AutoYaw::set_fixed_yaw(float angle_deg, float turn_rate_ds, int8_t direction, bool relative_angle)
 {
-    fixed_last_update = millis();
+    _last_update_ms = millis();
 
     _yaw_angle_cd = copter.attitude_control->get_att_target_euler_cd().z;
     _yaw_rate_cds = 0.0;
 
     // calculate final angle as relative to vehicle heading or absolute
     if (relative_angle) {
-        if (direction == 0) {
-            _fixed_yaw_offset_cd = angle_deg;
-        } else {
-            _fixed_yaw_offset_cd = angle_deg * direction;
-        }
+        _fixed_yaw_offset_cd = angle_deg * 100.0 * (direction >= 0 ? 1.0 : -1.0);
     } else {
         // absolute angle
         _fixed_yaw_offset_cd = wrap_180_cd(angle_deg * 100.0 - _yaw_angle_cd);
@@ -134,7 +130,7 @@ void Mode::AutoYaw::set_fixed_yaw(float angle_deg, float turn_rate_ds, int8_t di
 // set_fixed_yaw - sets the yaw look at heading for auto mode
 void Mode::AutoYaw::set_yaw_angle_rate(float yaw_angle_d, float yaw_rate_ds)
 {
-    fixed_last_update = millis();
+    _last_update_ms = millis();
 
     _yaw_angle_cd = yaw_angle_d * 100.0;
     _yaw_rate_cds = yaw_rate_ds * 100.0;
@@ -201,8 +197,9 @@ float Mode::AutoYaw::yaw()
     case AUTO_YAW_FIXED: {
         // keep heading pointing in the direction held in fixed_yaw
         // with no pilot input allowed
-        float dt = millis() - fixed_last_update;
-        fixed_last_update = millis();
+        const uint32_t now_ms = millis();
+        float dt = now_ms - _last_update_ms;
+        _last_update_ms = now_ms;
         float yaw_angle_step = constrain_float(_fixed_yaw_offset_cd, - dt * _fixed_yaw_slewrate_cds, dt * _fixed_yaw_slewrate_cds);
         _fixed_yaw_offset_cd -= yaw_angle_step;
         _yaw_angle_cd += yaw_angle_step;
@@ -227,8 +224,9 @@ float Mode::AutoYaw::yaw()
         return wrap_360_cd(copter.attitude_control->get_att_target_euler_cd().z);
 
     case AUTO_YAW_ANGLE_RATE:{
-        float dt = millis() - fixed_last_update;
-        fixed_last_update = millis();
+        const uint32_t now_ms = millis();
+        float dt = now_ms - _last_update_ms;
+        _last_update_ms = now_ms;
         _yaw_angle_cd += _yaw_rate_cds * dt;
         return _yaw_angle_cd;
     }

ArduCopter/mode.h

@@ -226,7 +226,8 @@ public:
         // Deg/s we should turn
         float _fixed_yaw_slewrate_cds;
 
-        uint32_t fixed_last_update;
+        // time of the last yaw update
+        uint32_t _last_update_ms;
 
         // heading when in yaw_look_ahead_yaw
         float _look_ahead_yaw;