AP_Compass: BeagleBone Blue add external compass HMC5843

libraries/AP_Compass/AP_Compass.cpp

@@ -659,6 +659,11 @@ void Compass::_detect_backends(void)
                  AP_Compass_AK8963::name, false);
     ADD_BACKEND(AP_Compass_HMC5843::probe(*this, hal.i2c_mgr->get_device(HAL_COMPASS_HMC5843_I2C_BUS, HAL_COMPASS_HMC5843_I2C_ADDR), true),
                  AP_Compass_HMC5843::name, true);
+#elif CONFIG_HAL_BOARD_SUBTYPE == HAL_BOARD_SUBTYPE_LINUX_BLUE
+    ADD_BACKEND(AP_Compass_AK8963::probe_mpu9250(*this, hal.i2c_mgr->get_device(HAL_COMPASS_AK8963_I2C_BUS, HAL_COMPASS_AK8963_I2C_ADDR)),
+                 AP_Compass_AK8963::name, false);
+    ADD_BACKEND(AP_Compass_HMC5843::probe(*this, hal.i2c_mgr->get_device(HAL_COMPASS_HMC5843_I2C_BUS, HAL_COMPASS_HMC5843_I2C_ADDR), true),
+                 AP_Compass_HMC5843::name, true);
 #elif HAL_COMPASS_DEFAULT == HAL_COMPASS_AK8963_MPU9250
     ADD_BACKEND(AP_Compass_AK8963::probe_mpu9250(*this, 0),
                  AP_Compass_AK8963::name, false);