diff --git a/src/drivers/drv_pwm_output.h b/src/drivers/drv_pwm_output.h
index c3eea310ff..7a93e513ed 100644
--- a/src/drivers/drv_pwm_output.h
+++ b/src/drivers/drv_pwm_output.h
@@ -160,7 +160,7 @@ ORB_DECLARE(output_pwm);
 
 #define DSM2_BIND_PULSES 3	/* DSM_BIND_START ioctl parameter, pulses required to start dsm2 pairing */
 #define DSMX_BIND_PULSES 7	/* DSM_BIND_START ioctl parameter, pulses required to start dsmx pairing */
-#define DSMX8_BIND_PULSES 10	/* DSM_BIND_START ioctl parameter, pulses required to start 8 or more channel dsmx pairing */
+#define DSMX8_BIND_PULSES 10 	/* DSM_BIND_START ioctl parameter, pulses required to start 8 or more channel dsmx pairing */
 
 /** power up DSM receiver */
 #define DSM_BIND_POWER_UP _IOC(_PWM_SERVO_BASE, 11)
diff --git a/src/drivers/px4io/px4io.cpp b/src/drivers/px4io/px4io.cpp
index efcf4d12b9..7c7b3dcb7d 100644
--- a/src/drivers/px4io/px4io.cpp
+++ b/src/drivers/px4io/px4io.cpp
@@ -244,8 +244,7 @@ private:
 	volatile int		_task;			///< worker task id
 	volatile bool		_task_should_exit;	///< worker terminate flag
 
-	int			_mavlink_fd;		///< mavlink file descriptor. This is opened by class instantiation and Doesn't appear to be usable in main thread.
-	int			_thread_mavlink_fd;	///< mavlink file descriptor for thread.
+	int			_mavlink_fd;		///< mavlink file descriptor.
 
 	perf_counter_t		_perf_update;		///<local performance counter for status updates
 	perf_counter_t		_perf_write;		///<local performance counter for PWM control writes
@@ -474,7 +473,6 @@ PX4IO::PX4IO(device::Device *interface) :
 	_task(-1),
 	_task_should_exit(false),
 	_mavlink_fd(-1),
-	_thread_mavlink_fd(-1),
 	_perf_update(perf_alloc(PC_ELAPSED, "io update")),
 	_perf_write(perf_alloc(PC_ELAPSED, "io write")),
 	_perf_chan_count(perf_alloc(PC_COUNT, "io rc #")),
@@ -507,9 +505,6 @@ PX4IO::PX4IO(device::Device *interface) :
 	/* we need this potentially before it could be set in task_main */
 	g_dev = this;
 
-	/* open MAVLink text channel */
-	_mavlink_fd = ::open(MAVLINK_LOG_DEVICE, 0);
-
 	_debug_enabled = false;
 	_servorail_status.rssi_v = 0;
 }
@@ -785,7 +780,7 @@ PX4IO::task_main()
 	hrt_abstime poll_last = 0;
 	hrt_abstime orb_check_last = 0;
 
-	_thread_mavlink_fd = ::open(MAVLINK_LOG_DEVICE, 0);
+	_mavlink_fd = ::open(MAVLINK_LOG_DEVICE, 0);
 
 	/*
 	 * Subscribe to the appropriate PWM output topic based on whether we are the
@@ -880,6 +875,10 @@ PX4IO::task_main()
 			/* run at 5Hz */
 			orb_check_last = now;
 
+			/* try to claim the MAVLink log FD */
+			if (_mavlink_fd < 0)
+				_mavlink_fd = ::open(MAVLINK_LOG_DEVICE, 0);
+
 			/* check updates on uORB topics and handle it */
 			bool updated = false;
 
@@ -1275,16 +1274,14 @@ void
 PX4IO::dsm_bind_ioctl(int dsmMode)
 {
 	if (!(_status & PX4IO_P_STATUS_FLAGS_SAFETY_OFF)) {
-		/* 0: dsm2, 1:dsmx */
-		if ((dsmMode == 0) || (dsmMode == 1)) {
-			mavlink_log_info(_thread_mavlink_fd, "[IO] binding dsm%s rx", (dsmMode == 0) ? "2" : ((dsmMode == 1) ? "x" : "x8"));
-			ioctl(nullptr, DSM_BIND_START, (dsmMode == 0) ? DSM2_BIND_PULSES : ((dsmMode == 1) ? DSMX_BIND_PULSES : DSMX8_BIND_PULSES));
-		} else {
-			mavlink_log_info(_thread_mavlink_fd, "[IO] invalid dsm bind mode, bind request rejected");
-		}
+		mavlink_log_info(_mavlink_fd, "[IO] binding DSM%s RX", (dsmMode == 0) ? "2" : ((dsmMode == 1) ? "-X" : "-X8"));
+		int ret = ioctl(nullptr, DSM_BIND_START, (dsmMode == 0) ? DSM2_BIND_PULSES : ((dsmMode == 1) ? DSMX_BIND_PULSES : DSMX8_BIND_PULSES));
+
+		if (ret)
+			mavlink_log_critical(_mavlink_fd, "binding failed.");
 
 	} else {
-		mavlink_log_info(_thread_mavlink_fd, "[IO] system armed, bind request rejected");
+		mavlink_log_info(_mavlink_fd, "[IO] system armed, bind request rejected");
 	}
 }
 
@@ -2115,14 +2112,24 @@ PX4IO::ioctl(file * /*filep*/, int cmd, unsigned long arg)
 		break;
 
 	case DSM_BIND_START:
-		io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_power_down);
-		usleep(500000);
-		io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_set_rx_out);
-		io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_power_up);
-		usleep(72000);
-		io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_send_pulses | (arg << 4));
-		usleep(50000);
-		io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_reinit_uart);
+
+		/* only allow DSM2, DSM-X and DSM-X with more than 7 channels */
+		if (arg == DSM2_BIND_PULSES ||
+		    arg == DSMX_BIND_PULSES ||
+		    arg == DSMX8_BIND_PULSES) {
+			io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_power_down);
+			usleep(500000);
+			io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_set_rx_out);
+			io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_power_up);
+			usleep(72000);
+			io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_send_pulses | (arg << 4));
+			usleep(50000);
+			io_reg_set(PX4IO_PAGE_SETUP, PX4IO_P_SETUP_DSM, dsm_bind_reinit_uart);
+
+			ret = OK;
+		} else {
+			ret = -EINVAL;
+		}
 		break;
 
 	case DSM_BIND_POWER_UP:
@@ -2615,7 +2622,7 @@ bind(int argc, char *argv[])
 #endif
 
 	if (argc < 3)
-		errx(0, "needs argument, use dsm2 or dsmx");
+		errx(0, "needs argument, use dsm2, dsmx or dsmx8");
 
 	if (!strcmp(argv[2], "dsm2"))
 		pulses = DSM2_BIND_PULSES;
@@ -2624,7 +2631,7 @@ bind(int argc, char *argv[])
 	else if (!strcmp(argv[2], "dsmx8"))
 		pulses = DSMX8_BIND_PULSES;
 	else 
-		errx(1, "unknown parameter %s, use dsm2 or dsmx", argv[2]);
+		errx(1, "unknown parameter %s, use dsm2, dsmx or dsmx8", argv[2]);
 	// Test for custom pulse parameter
 	if (argc > 3)
 		pulses = atoi(argv[3]);
diff --git a/src/modules/px4iofirmware/registers.c b/src/modules/px4iofirmware/registers.c
index 1335f52e13..97d25bbfa8 100644
--- a/src/modules/px4iofirmware/registers.c
+++ b/src/modules/px4iofirmware/registers.c
@@ -566,7 +566,7 @@ registers_set_one(uint8_t page, uint8_t offset, uint16_t value)
 			break;
 
 		case PX4IO_P_SETUP_DSM:
-			dsm_bind(value & 0x0f, (value >> 4) & 7);
+			dsm_bind(value & 0x0f, (value >> 4) & 0xF);
 			break;
 
 		default: