diff --git a/libraries/AP_Compass/AP_Compass.cpp b/libraries/AP_Compass/AP_Compass.cpp
index b7132a3518..ddbdf6d7ca 100644
--- a/libraries/AP_Compass/AP_Compass.cpp
+++ b/libraries/AP_Compass/AP_Compass.cpp
@@ -494,15 +494,30 @@ void Compass::_detect_backends(void)
 #elif HAL_COMPASS_DEFAULT == HAL_COMPASS_PX4 || HAL_COMPASS_DEFAULT == HAL_COMPASS_VRBRAIN
     if (AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_TEST_V1 ||
         AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_TEST_V2 ||
+        AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_TEST_V3 ||
         AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_TEST_V4) {
-        // use in-tree driver
+        // external i2c bus
         _add_backend(AP_Compass_HMC5843::probe(*this, hal.i2c_mgr->get_device(1, HAL_COMPASS_HMC5843_I2C_ADDR), true),
                          AP_Compass_HMC5843::name, true);
+        // internal i2c bus
+        _add_backend(AP_Compass_HMC5843::probe(*this, hal.i2c_mgr->get_device(0, HAL_COMPASS_HMC5843_I2C_ADDR), false),
+                         AP_Compass_HMC5843::name, false);
+        // try for SPI device too
+        _add_backend(AP_Compass_HMC5843::probe(*this, hal.spi->get_device(HAL_COMPASS_HMC5843_NAME), false),
+                     AP_Compass_HMC5843::name, false);
     }
     if (AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_TEST_V2) {
         _add_backend(AP_Compass_LSM303D::probe(*this, hal.spi->get_device(HAL_INS_LSM9DS0_A_NAME)),
                      AP_Compass_LSM303D::name, false);
     }
+    if (AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_TEST_V3) {
+        _add_backend(AP_Compass_LSM303D::probe(*this, hal.spi->get_device(HAL_INS_LSM9DS0_EXT_A_NAME)),
+                     AP_Compass_LSM303D::name, false);
+        _add_backend(AP_Compass_AK8963::probe_mpu9250(*this, 0),
+                     AP_Compass_AK8963::name, false);
+        _add_backend(AP_Compass_AK8963::probe_mpu9250(*this, 1),
+                     AP_Compass_AK8963::name, false);
+    }
     if (AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_TEST_V4) {
         _add_backend(AP_Compass_AK8963::probe_mpu9250(*this, 0),
                      AP_Compass_AK8963::name, false);
diff --git a/libraries/AP_Compass/AP_Compass_HMC5843.cpp b/libraries/AP_Compass/AP_Compass_HMC5843.cpp
index f17d4298f5..76c450aa7c 100644
--- a/libraries/AP_Compass/AP_Compass_HMC5843.cpp
+++ b/libraries/AP_Compass/AP_Compass_HMC5843.cpp
@@ -102,7 +102,7 @@ AP_Compass_HMC5843::~AP_Compass_HMC5843()
 }
 
 AP_Compass_Backend *AP_Compass_HMC5843::probe(Compass &compass,
-                                              AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev,
+                                              AP_HAL::OwnPtr<AP_HAL::Device> dev,
                                               bool force_external)
 {
     AP_HMC5843_BusDriver *bus = new AP_HMC5843_BusDriver_HALDevice(std::move(dev));
@@ -475,8 +475,8 @@ bool AP_Compass_HMC5843::_calibrate()
     return success;
 }
 
-/* AP_HAL::I2CDevice implementation of the HMC5843 */
-AP_HMC5843_BusDriver_HALDevice::AP_HMC5843_BusDriver_HALDevice(AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev)
+/* AP_HAL::Device implementation of the HMC5843 */
+AP_HMC5843_BusDriver_HALDevice::AP_HMC5843_BusDriver_HALDevice(AP_HAL::OwnPtr<AP_HAL::Device> dev)
     : _dev(std::move(dev))
 {
 }
diff --git a/libraries/AP_Compass/AP_Compass_HMC5843.h b/libraries/AP_Compass/AP_Compass_HMC5843.h
index bb510c4e88..8086bd86be 100644
--- a/libraries/AP_Compass/AP_Compass_HMC5843.h
+++ b/libraries/AP_Compass/AP_Compass_HMC5843.h
@@ -2,7 +2,7 @@
 
 #include <AP_Common/AP_Common.h>
 #include <AP_HAL/AP_HAL.h>
-#include <AP_HAL/I2CDevice.h>
+#include <AP_HAL/Device.h>
 #include <AP_Math/AP_Math.h>
 
 #include "AP_Compass.h"
@@ -17,7 +17,7 @@ class AP_Compass_HMC5843 : public AP_Compass_Backend
 {
 public:
     static AP_Compass_Backend *probe(Compass &compass,
-                                     AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev,
+                                     AP_HAL::OwnPtr<AP_HAL::Device> dev,
                                      bool force_external = false);
 
     static AP_Compass_Backend *probe_mpu6000(Compass &compass);
@@ -88,7 +88,7 @@ public:
 class AP_HMC5843_BusDriver_HALDevice : public AP_HMC5843_BusDriver
 {
 public:
-    AP_HMC5843_BusDriver_HALDevice(AP_HAL::OwnPtr<AP_HAL::I2CDevice> dev);
+    AP_HMC5843_BusDriver_HALDevice(AP_HAL::OwnPtr<AP_HAL::Device> dev);
 
     bool block_read(uint8_t reg, uint8_t *buf, uint32_t size) override;
     bool register_read(uint8_t reg, uint8_t *val) override;
@@ -99,7 +99,7 @@ public:
     AP_HAL::Device::PeriodicHandle register_periodic_callback(uint32_t period_usec, AP_HAL::Device::PeriodicCb) override;
     
 private:
-    AP_HAL::OwnPtr<AP_HAL::I2CDevice> _dev;
+    AP_HAL::OwnPtr<AP_HAL::Device> _dev;
 };
 
 class AP_HMC5843_BusDriver_Auxiliary : public AP_HMC5843_BusDriver