SITL: support -roll180 option to frames

libraries/SITL/SIM_Aircraft.cpp

@@ -73,6 +73,11 @@ Aircraft::Aircraft(const char *home_str, const char *frame_str) :
     last_wall_time_us = get_wall_time_us();
     frame_counter = 0;
 
+    // support rotated IMUs for testing
+    if (strstr(frame_str, "-roll180")) {
+        imu_rotation = ROTATION_ROLL_180;
+    }
+    
     terrain = (AP_Terrain *)AP_Param::find_object("TERRAIN_");
 }
 
@@ -379,6 +384,20 @@ void Aircraft::fill_fdm(struct sitl_fdm &fdm)
         fdm.altitude  = smoothing.location.alt * 1.0e-2;
     }
 
+    if (imu_rotation != ROTATION_NONE) {
+        Vector3f accel(fdm.xAccel, fdm.yAccel, fdm.zAccel);
+        accel.rotate(imu_rotation);
+        fdm.xAccel    = accel.x;
+        fdm.yAccel    = accel.y;
+        fdm.zAccel    = accel.z;
+
+        Vector3f rgyro(fdm.rollRate, fdm.pitchRate, fdm.yawRate);
+        rgyro.rotate(imu_rotation);
+        fdm.rollRate  = degrees(rgyro.x);
+        fdm.pitchRate = degrees(rgyro.y);
+        fdm.yawRate   = degrees(rgyro.z);
+    }
+    
     if (last_speedup != sitl->speedup && sitl->speedup > 0) {
         set_speedup(sitl->speedup);
         last_speedup = sitl->speedup;

libraries/SITL/SIM_Aircraft.h

@@ -164,6 +164,8 @@ protected:
     bool use_time_sync = true;
     float last_speedup = -1.0f;
 
+    enum Rotation imu_rotation = ROTATION_NONE;
+
     enum {
         GROUND_BEHAVIOR_NONE = 0,
         GROUND_BEHAVIOR_NO_MOVEMENT,