diff --git a/nuttx-configs/px4fmu-v4/include/board.h b/nuttx-configs/px4fmu-v4/include/board.h
index 2f7c1189f3..1eb9fc9146 100755
--- a/nuttx-configs/px4fmu-v4/include/board.h
+++ b/nuttx-configs/px4fmu-v4/include/board.h
@@ -215,7 +215,7 @@
 #define GPIO_UART4_RX	GPIO_UART4_RX_1
 #define GPIO_UART4_TX	GPIO_UART4_TX_1
 
-#define GPIO_USART6_RX	GPIO_USART6_RX_1
+#define GPIO_USART6_RX	GPIO_USART6_RX_1	/* RC_INPUT */
 #define GPIO_USART6_TX	GPIO_USART6_TX_1
 
 #define GPIO_UART7_RX	GPIO_UART7_RX_1
diff --git a/src/drivers/boards/px4fmu-v4/board_config.h b/src/drivers/boards/px4fmu-v4/board_config.h
index 03afcda0b4..65d0aa4532 100644
--- a/src/drivers/boards/px4fmu-v4/board_config.h
+++ b/src/drivers/boards/px4fmu-v4/board_config.h
@@ -240,11 +240,14 @@ __BEGIN_DECLS
 
 /* Power switch controls ******************************************************/
 
-#define POWER_SPEKTRUM(_s)		stm32_gpiowrite(GPIO_SPEKTRUM_PWR_EN, (1-_s))
-#define GPIO_USART1_RX_SPEKTRUM		(GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_SET|GPIO_PORTC|GPIO_PIN7)
-#define SPEKTRUM_RX_HIGH(_s)	stm32_gpiowrite(GPIO_USART1_RX_SPEKTRUM, (_s))
+#define POWER_SPEKTRUM(_s)			stm32_gpiowrite(GPIO_SPEKTRUM_PWR_EN, (1-_s))
+//#define GPIO_USART1_RX_SPEKTRUM		(GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_SET|GPIO_PORTC|GPIO_PIN7)
 #define SPEKTRUM_RX_AS_UART()		stm32_configgpio(GPIO_USART1_RX)
-#define SPEKTRUM_RX_AS_GPIO()		stm32_configgpio(GPIO_USART1_RX_SPEKTRUM)
+
+// FMUv4 has a separate GPIO for serial RC output
+#define GPIO_RC_OUT					(GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_CLEAR|GPIO_PORTC|GPIO_PIN6)
+#define SPEKTRUM_RX_AS_GPIO()		stm32_configgpio(GPIO_RC_OUT)
+#define SPEKTRUM_RX_HIGH(_s)		stm32_gpiowrite(GPIO_RC_OUT, (_s))
 
 /****************************************************************************************************
  * Public Types
diff --git a/src/drivers/boards/px4fmu-v4/px4fmu_init.c b/src/drivers/boards/px4fmu-v4/px4fmu_init.c
index d093e47bf4..12f107b308 100644
--- a/src/drivers/boards/px4fmu-v4/px4fmu_init.c
+++ b/src/drivers/boards/px4fmu-v4/px4fmu_init.c
@@ -233,6 +233,10 @@ __EXPORT int nsh_archinitialize(void)
 	stm32_configgpio(GPIO_SPEKTRUM_PWR_EN);
 	stm32_configgpio(GPIO_8266_PD);
 	stm32_configgpio(GPIO_8266_RST);
+#ifdef GPIO_RC_OUT
+	stm32_configgpio(GPIO_RC_OUT);      /* Serial RC output pin */
+	stm32_gpiowrite(GPIO_RC_OUT, 1);    /* set it high to pull RC input up */
+#endif
 
 	/* configure the high-resolution time/callout interface */
 	hrt_init();