diff --git a/ROMFS/px4fmu_common/init.d/rc.sensors b/ROMFS/px4fmu_common/init.d/rc.sensors
index a764dfa5a0..2413933c69 100644
--- a/ROMFS/px4fmu_common/init.d/rc.sensors
+++ b/ROMFS/px4fmu_common/init.d/rc.sensors
@@ -107,8 +107,11 @@ fi
 
 if ver hwcmp NXPHLITE_V3
 then
-	# Internal I2C (baro)
-	mpl3115a2 -I start
+	# External I2C bus
+	hmc5883 -C -X start
+
+	# Onboard I2C (baro) but an external bus on V3 RC15
+	mpl3115a2 -X start
 
 	# Internal SPI (accel + mag)
 	fxos8701cq start -a 8 -R 0
diff --git a/src/drivers/boards/nxphlite-v3/board_config.h b/src/drivers/boards/nxphlite-v3/board_config.h
index 894ef99e24..a58b4f8987 100644
--- a/src/drivers/boards/nxphlite-v3/board_config.h
+++ b/src/drivers/boards/nxphlite-v3/board_config.h
@@ -259,9 +259,9 @@ __BEGIN_DECLS
 /* I2C busses */
 
 #define PX4_I2C_BUS_EXPANSION               PX4_BUS_NUMBER_TO_PX4(0)
-#define PX4_I2C_BUS_ONBOARD                 PX4_BUS_NUMBER_TO_PX4(1)
-
-#define PX4_I2C_BUS_LED                     PX4_I2C_BUS_EXPANSION
+#define PX4_I2C_BUS_EXPANSION1              PX4_BUS_NUMBER_TO_PX4(1) // V3 RC15 has mpl3115a2 on onboard but this goes to a connector
+// So it is treated as external.
+#define PX4_I2C_BUS_LED                     PX4_I2C_BUS_EXPANSION1
 
 /*
  * ADC channels