AP_Compass: added AK09918 support

minor update over AK09916

libraries/AP_Compass/AP_Compass_AK09916.cpp

@@ -50,6 +50,7 @@ extern const AP_HAL::HAL &hal;
 #define ICM_WHOAMI_VAL      0xEA
 
 #define AK09916_Device_ID   0x09
+#define AK09918_Device_ID   0x0c
 #define AK09916_MILLIGAUSS_SCALE 10.0f
 
 extern const AP_HAL::HAL &hal;
@@ -227,7 +228,7 @@ bool AP_Compass_AK09916::init()
     _initialized = true;
 
     /* register the compass instance in the frontend */
-    _bus->set_device_type(DEVTYPE_AK09916);
+    _bus->set_device_type(_devtype);
     if (!register_compass(_bus->get_bus_id(), _compass_instance)) {
         goto fail;
     }
@@ -315,9 +316,15 @@ bool AP_Compass_AK09916::_check_id()
         uint8_t deviceid = 0;
 
         /* Read AK09916's id */
-        if (_bus->register_read(REG_DEVICE_ID, &deviceid) &&
-            deviceid == AK09916_Device_ID) {
-            return true;
+        if (_bus->register_read(REG_DEVICE_ID, &deviceid)) {
+            switch (deviceid) {
+            case AK09916_Device_ID:
+                _devtype = DEVTYPE_AK09916;
+                return true;
+            case AK09918_Device_ID:
+                _devtype = DEVTYPE_AK09918;
+                return true;
+            }
         }
     }
 

libraries/AP_Compass/AP_Compass_AK09916.h

@@ -82,6 +82,7 @@ private:
     uint8_t _compass_instance;
     bool _initialized;
     enum Rotation _rotation;
+    enum AP_Compass_Backend::DevTypes _devtype;
 };
 
 

libraries/AP_Compass/AP_Compass_Backend.h

@@ -65,6 +65,7 @@ public:
         DEVTYPE_RM3100 = 0x11,
         DEVTYPE_RM3100_2 = 0x12, // unused, past mistake
         DEVTYPE_MMC5883 = 0x13,
+        DEVTYPE_AK09918 = 0x14,
     };
 
 #if HAL_MSP_COMPASS_ENABLED