diff --git a/src/drivers/boards/px4fmu-v4/board_config.h b/src/drivers/boards/px4fmu-v4/board_config.h
index d57396a8fd..d464c8af2a 100644
--- a/src/drivers/boards/px4fmu-v4/board_config.h
+++ b/src/drivers/boards/px4fmu-v4/board_config.h
@@ -215,7 +215,7 @@ __BEGIN_DECLS
 #define HRT_PPM_CHANNEL		3	/* use capture/compare channel 2 */
 #define GPIO_PPM_IN			(GPIO_ALT|GPIO_AF2|GPIO_PULLUP|GPIO_PORTB|GPIO_PIN0)
 
-#define SBUS_SERIAL_PORT	"/dev/ttyS4"
+#define RC_SERIAL_PORT		"/dev/ttyS4"
 
 /* PWM input driver. Use FMU AUX5 pins attached to timer4 channel 2 */
 #define PWMIN_TIMER			4
@@ -226,7 +226,10 @@ __BEGIN_DECLS
 #define GPIO_LED_SAFETY			(GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_CLEAR|GPIO_PORTC|GPIO_PIN3)
 #define GPIO_BTN_SAFETY			(GPIO_INPUT|GPIO_PULLUP|GPIO_PORTC|GPIO_PIN4)
 #define GPIO_PERIPH_3V3_EN		(GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_SET|GPIO_PORTC|GPIO_PIN5)
+/* for R07, this signal is active low */
 #define GPIO_SBUS_INV			(GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_CLEAR|GPIO_PORTC|GPIO_PIN13)
+/* for R12, this signal is active high */
+//#define GPIO_SBUS_INV			(GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_SET|GPIO_PORTC|GPIO_PIN13)
 
 #define GPIO_8266_GPIO0			(GPIO_INPUT|GPIO_PULLUP|GPIO_PORTE|GPIO_PIN2)
 #define GPIO_SPEKTRUM_PWR_EN		(GPIO_OUTPUT|GPIO_PUSHPULL|GPIO_SPEED_2MHz|GPIO_OUTPUT_CLEAR|GPIO_PORTE|GPIO_PIN4)
diff --git a/src/drivers/px4fmu/fmu.cpp b/src/drivers/px4fmu/fmu.cpp
index 05d7047c97..9747cd660c 100644
--- a/src/drivers/px4fmu/fmu.cpp
+++ b/src/drivers/px4fmu/fmu.cpp
@@ -631,19 +631,9 @@ PX4FMU::cycle()
 
 		update_pwm_rev_mask();
 
-#ifdef SBUS_SERIAL_PORT
-		_sbus_fd = sbus_init(SBUS_SERIAL_PORT, false);
-#endif
-
-#ifdef DSM_SERIAL_PORT
-		// XXX rather than opening it we need to cycle between protocols until one is locked in
-		//_dsm_fd = dsm_init(DSM_SERIAL_PORT);
-#endif
-
 		_initialized = true;
 	}
 
-
 	if (_groups_subscribed != _groups_required) {
 		subscribe();
 		_groups_subscribed = _groups_required;
@@ -811,15 +801,18 @@ PX4FMU::cycle()
 
 	bool rc_updated = false;
 
-#ifdef SBUS_SERIAL_PORT
+#ifdef RC_SERIAL_PORT
 	bool sbus_failsafe, sbus_frame_drop;
 	uint16_t raw_rc_values[input_rc_s::RC_INPUT_MAX_CHANNELS];
 	uint16_t raw_rc_count;
-	bool sbus_updated = sbus_input(_sbus_fd, &raw_rc_values[0], &raw_rc_count, &sbus_failsafe, &sbus_frame_drop,
+
+	// read port
+	bool sbus_updated = sbus_input(_sbus_fd, &raw_rc_values[0], &raw_rc_count,
+				       &sbus_failsafe, &sbus_frame_drop,
 				       input_rc_s::RC_INPUT_MAX_CHANNELS);
 
 	if (sbus_updated) {
-		// we have a new PPM frame. Publish it.
+		// we have a new SBUS frame. Publish it.
 		_rc_in.channel_count = raw_rc_count;
 
 		if (_rc_in.channel_count > input_rc_s::RC_INPUT_MAX_CHANNELS) {
@@ -848,8 +841,8 @@ PX4FMU::cycle()
 #ifdef HRT_PPM_CHANNEL
 
 	// see if we have new PPM input data
-	if ((ppm_last_valid_decode != _rc_in.timestamp_last_signal) &&
-	    ppm_decoded_channels > 3) {
+	if ((ppm_last_valid_decode != _rc_in.timestamp_last_signal)
+	    && ppm_decoded_channels > 3) {
 		// we have a new PPM frame. Publish it.
 		_rc_in.channel_count = ppm_decoded_channels;
 
@@ -2224,7 +2217,7 @@ fmu_main(int argc, char *argv[])
 	}
 
 	if (!strcmp(verb, "info")) {
-#ifdef SBUS_SERIAL_PORT
+#ifdef RC_SERIAL_PORT
 		warnx("frame drops: %u", sbus_dropped_frames());
 #endif
 		return 0;