diff --git a/src/drivers/px4fmu/fmu.cpp b/src/drivers/px4fmu/fmu.cpp
index abb3a36898..5f5ea7e0a2 100644
--- a/src/drivers/px4fmu/fmu.cpp
+++ b/src/drivers/px4fmu/fmu.cpp
@@ -405,13 +405,15 @@ PX4FMU::init()
 		return ret;
 	}
 
-	/* try to claim the generic PWM output device node as well - it's OK if we fail at this */
-	_class_instance = register_class_devname(PWM_OUTPUT_BASE_DEVICE_PATH);
+	if (_mode != MODE_NONE) {
+		/* try to claim the generic PWM output device node as well - it's OK if we fail at this */
+		_class_instance = register_class_devname(PWM_OUTPUT_BASE_DEVICE_PATH);
 
-	if (_class_instance == CLASS_DEVICE_PRIMARY) {
-		/* lets not be too verbose */
-	} else if (_class_instance < 0) {
-		warnx("FAILED registering class device");
+		if (_class_instance == CLASS_DEVICE_PRIMARY) {
+			/* lets not be too verbose */
+		} else if (_class_instance < 0) {
+			warnx("FAILED registering class device");
+		}
 	}
 
 	_safety_disabled = circuit_breaker_enabled("CBRK_IO_SAFETY", CBRK_IO_SAFETY_KEY);
@@ -422,7 +424,7 @@ PX4FMU::init()
 }
 
 void
-PX4FMU:: safety_check_button(void)
+PX4FMU::safety_check_button(void)
 {
 #ifdef GPIO_BTN_SAFETY
 	static int counter = 0;
@@ -859,10 +861,12 @@ void PX4FMU::rc_io_invert(bool invert)
 {
 	INVERT_RC_INPUT(invert);
 
+#ifdef GPIO_RC_OUT
 	if (!invert) {
 		// set FMU_RC_OUTPUT high to pull RC_INPUT up
 		px4_arch_gpiowrite(GPIO_RC_OUT, 1);
 	}
+#endif
 }
 #endif
 
@@ -907,8 +911,10 @@ PX4FMU::cycle()
 		_rcs_fd = dsm_init(RC_SERIAL_PORT);
 		// assume SBUS input
 		sbus_config(_rcs_fd, false);
+#ifdef GPIO_PPM_IN
 		// disable CPPM input by mapping it away from the timer capture input
 		px4_arch_unconfiggpio(GPIO_PPM_IN);
+#endif
 #endif
 
 		_initialized = true;
@@ -2017,7 +2023,7 @@ PX4FMU::pwm_ioctl(file *filp, int cmd, unsigned long arg)
 			break;
 		}
 
-#ifdef RC_SERIAL_PORT
+#ifdef GPIO_SPEKTRUM_PWR_EN
 
 	case DSM_BIND_START:
 		/* only allow DSM2, DSM-X and DSM-X with more than 7 channels */
@@ -2960,6 +2966,9 @@ fmu_main(int argc, char *argv[])
 	if (!strcmp(verb, "mode_gpio")) {
 		new_mode = PORT_FULL_GPIO;
 
+	} else if (!strcmp(verb, "mode_rcin")) {
+		exit(0);
+
 	} else if (!strcmp(verb, "mode_pwm")) {
 		new_mode = PORT_FULL_PWM;
 
@@ -3050,12 +3059,16 @@ fmu_main(int argc, char *argv[])
 		exit(0);
 	}
 
-	fprintf(stderr, "FMU: unrecognised command %s, try:\n", verb);
+	fprintf(stderr, "FMU: unrecognized command %s, try:\n", verb);
+#if defined(RC_SERIAL_PORT)
+	fprintf(stderr, " mode_rcin");
+#endif
 #if defined(BOARD_HAS_MULTI_PURPOSE_GPIO)
 	fprintf(stderr,
-		"  mode_gpio, mode_serial, mode_pwm, mode_gpio_serial, mode_pwm_serial, mode_pwm_gpio, test, fake, sensor_reset, id\n");
+		" , mode_gpio, mode_serial, mode_pwm, mode_gpio_serial, mode_pwm_serial, mode_pwm_gpio, test, fake, sensor_reset, id\n");
 #elif defined(BOARD_HAS_PWM) && BOARD_HAS_PWM >= 6
-	fprintf(stderr, "  mode_gpio, mode_pwm, mode_pwm4, test, sensor_reset [milliseconds], i2c <bus> <hz>\n");
+	fprintf(stderr, " mode_gpio, mode_pwm, mode_pwm4, test, sensor_reset [milliseconds], i2c <bus> <hz>\n");
 #endif
+	fprintf(stderr, "\n");
 	exit(1);
 }