[rotorcraft] separate KILL_ON_GROUND_DETECT with higher default threshold

- if KILL_ON_GROUND_DETECT is TRUE, enable killing of motors on ground detection
  used in default land block, add to your airframe file:
  <define name="KILL_ON_GROUND_DETECT" value="TRUE"/>
- THRESHOLD_GROUND_DETECT is now in m/s^2 and defaults to 25 m/s^2

conf/airframes/fraser_lisa_m_rotorcraft.xml

@@ -32,6 +32,8 @@
 
     <!-- print the configuration during compiling -->
     <define name="PRINT_CONFIG"/>
+
+	<define name="KILL_ON_GROUND_DETECT" value="TRUE"/>
   </firmware>
 
   <firmware name="setup">
@@ -238,7 +240,7 @@
   <section name="AUTOPILOT">
     <define name="MODE_MANUAL" value="AP_MODE_ATTITUDE_DIRECT"/>
     <define name="MODE_AUTO1"  value="AP_MODE_ATTITUDE_Z_HOLD"/>
-    <define name="MODE_AUTO2"  value="AP_MODE_HOVER_Z_HOLD"/>
+    <define name="MODE_AUTO2"  value="AP_MODE_NAV"/>
   </section>
 
   <section name="BAT">

sw/airborne/firmwares/rotorcraft/autopilot.c

@@ -95,7 +95,8 @@ void autopilot_init(void) {
 void autopilot_periodic(void) {
 
   RunOnceEvery(NAV_PRESCALER, nav_periodic_task());
-#ifdef FAILSAFE_GROUND_DETECT
+#if FAILSAFE_GROUND_DETECT
+INFO("Using FAILSAFE_GROUND_DETECT")
   if (autopilot_mode == AP_MODE_FAILSAFE && autopilot_detect_ground) {
     autopilot_set_mode(AP_MODE_KILL);
     autopilot_detect_ground = FALSE;
@@ -103,7 +104,7 @@ void autopilot_periodic(void) {
 #endif
 
   /* set failsafe commands, if in FAILSAFE or KILL mode */
-#ifndef FAILSAFE_GROUND_DETECT
+#if !FAILSAFE_GROUND_DETECT
   if (autopilot_mode == AP_MODE_KILL ||
       autopilot_mode == AP_MODE_FAILSAFE) {
 #else

sw/airborne/firmwares/rotorcraft/autopilot.h

@@ -139,14 +139,15 @@ extern uint16_t autopilot_flight_time;
 }
 #endif
 
-/** Ground detection based on accelerometers.
- */
+/** Z-acceleration threshold to detect ground in m/s^2 */
 #ifndef THRESHOLD_GROUND_DETECT
-#define THRESHOLD_GROUND_DETECT ACCEL_BFP_OF_REAL(15.)
+#define THRESHOLD_GROUND_DETECT 25.0
 #endif
+/** Ground detection based on vertical acceleration.
+ */
 static inline void DetectGroundEvent(void) {
   if (autopilot_mode == AP_MODE_FAILSAFE || autopilot_detect_ground_once) {
-    struct NedCoor_i* accel = stateGetAccelNed_i();
+    struct NedCoor_f* accel = stateGetAccelNed_f();
     if (accel->z < -THRESHOLD_GROUND_DETECT ||
         accel->z > THRESHOLD_GROUND_DETECT) {
       autopilot_detect_ground = TRUE;

sw/airborne/firmwares/rotorcraft/main.c

@@ -241,8 +241,7 @@ STATIC_INLINE void main_event( void ) {
   GpsEvent(on_gps_event);
 #endif
 
-#ifdef FAILSAFE_GROUND_DETECT
-INFO("Using FAILSAFE_GROUND_DETECT")
+#if FAILSAFE_GROUND_DETECT || KILL_ON_GROUND_DETECT
   DetectGroundEvent();
 #endif