Sensirion SDP3X airspeed / differential pressure sensor driver

cmake/configs/nuttx_px4fmu-v2_default.cmake

@@ -37,6 +37,7 @@ set(config_module_list
 	#drivers/hott/hott_sensors
 	#drivers/blinkm
 	drivers/airspeed
+	drivers/sdp3x_airspeed
 	drivers/ets_airspeed
 	drivers/meas_airspeed
 	drivers/frsky_telemetry

src/drivers/sdp3x_airspeed/CMakeLists.txt

@@ -0,0 +1,44 @@
+############################################################################
+#
+#   Copyright (c) 2017 PX4 Development Team. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+#
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in
+#    the documentation and/or other materials provided with the
+#    distribution.
+# 3. Neither the name PX4 nor the names of its contributors may be
+#    used to endorse or promote products derived from this software
+#    without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+# COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+############################################################################
+px4_add_module(
+	MODULE drivers__sdp3x_airspeed
+	MAIN sdp3x_airspeed
+	STACK_MAIN 1200
+	COMPILE_FLAGS
+	SRCS
+		SDP3X.cpp
+		SDP3X_main.cpp
+	DEPENDS
+		platforms__common
+	)
+# vim: set noet ft=cmake fenc=utf-8 ff=unix :

src/drivers/sdp3x_airspeed/SDP3X.cpp

@@ -0,0 +1,208 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2017 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#include "SDP3X.hpp"
+
+/**
+ * @file SDP3X.hpp
+ *
+ * Driver for Sensirion SDP3X Differential Pressure Sensor
+ *
+ */
+
+int
+SDP3X::probe()
+{
+	return !init_sdp3x();
+}
+
+int SDP3X::write_command(uint16_t command)
+{
+	uint8_t cmd[2];
+	cmd[0] = static_cast<uint8_t>(command >> 8);
+	cmd[1] = static_cast<uint8_t>(command & 0xff);
+	return transfer(&cmd[0], 2, nullptr, 0);
+}
+
+bool
+SDP3X::init_sdp3x()
+{
+	// step 1 - reset on broadcast
+	uint16_t prev_addr = get_address();
+	set_address(SDP3X_RESET_ADDR);
+	uint8_t reset_cmd = SDP3X_RESET_CMD;
+	int ret = transfer(&reset_cmd, 1, nullptr, 0);
+	set_address(prev_addr);
+
+	if (ret != PX4_OK) {
+		perf_count(_comms_errors);
+		PX4_ERR("reset failed");
+		return false;
+	}
+
+	// wait until sensor is ready
+	usleep(20000);
+
+	// step 2 - configure
+	ret = write_command(SDP3X_CONT_MEAS_AVG_MODE);
+
+	if (ret != PX4_OK) {
+		perf_count(_comms_errors);
+		PX4_ERR("config failed");
+		return false;
+	}
+
+	usleep(10000);
+
+	// step 3 - get scale
+	uint8_t val[9];
+	ret = transfer(nullptr, 0, &val[0], 9);
+
+	if (ret != PX4_OK) {
+		perf_count(_comms_errors);
+		PX4_ERR("get scale failed");
+		return false;
+	}
+
+	// Check the CRC
+	if (!crc(&val[0], 2, val[2]) || !crc(&val[3], 2, val[5]) || !crc(&val[6], 2, val[8])) {
+		perf_count(_comms_errors);
+		return false;
+	}
+
+	_scale = (((uint16_t)val[6]) << 8) | val[7];
+
+	return true;
+}
+
+int
+SDP3X::collect()
+{
+	perf_begin(_sample_perf);
+
+	// read 6 bytes from the sensor
+	uint8_t val[6];
+	int ret = transfer(nullptr, 0, &val[0], 6);
+
+	if (ret != PX4_OK) {
+		perf_count(_comms_errors);
+		return ret;
+	}
+
+	// Check the CRC
+	if (!crc(&val[0], 2, val[2]) || !crc(&val[3], 2, val[5])) {
+		perf_count(_comms_errors);
+		return EAGAIN;
+
+	} else {
+		ret = 0;
+	}
+
+	int16_t P = (((uint16_t)val[0]) << 8) | val[1];
+	int16_t temp = (((uint16_t)val[3]) << 8) | val[4];
+
+	float diff_press_pa_raw = static_cast<float>(P) / static_cast<float>(_scale);
+	float temperature_c = temp / static_cast<float>(SDP3X_SCALE_TEMPERATURE);
+
+	// the raw value still should be compensated for the known offset
+	diff_press_pa_raw -= _diff_pres_offset;
+
+	differential_pressure_s report;
+
+	// track maximum differential pressure measured (so we can work out top speed).
+	if (diff_press_pa_raw > _max_differential_pressure_pa) {
+		_max_differential_pressure_pa = diff_press_pa_raw;
+	}
+
+	report.timestamp = hrt_absolute_time();
+	report.error_count = perf_event_count(_comms_errors);
+	report.temperature = temperature_c;
+	report.differential_pressure_filtered_pa = _filter.apply(diff_press_pa_raw);
+	report.differential_pressure_raw_pa = diff_press_pa_raw;
+	report.max_differential_pressure_pa = _max_differential_pressure_pa;
+
+	if (_airspeed_pub != nullptr && !(_pub_blocked)) {
+		// publish it
+		orb_publish(ORB_ID(differential_pressure), _airspeed_pub, &report);
+	}
+
+	new_report(report);
+
+	// notify anyone waiting for data
+	poll_notify(POLLIN);
+
+	ret = OK;
+
+	perf_end(_sample_perf);
+
+	return ret;
+}
+
+void
+SDP3X::cycle()
+{
+	int ret = PX4_ERROR;
+
+	// measurement phase
+	ret = collect();
+
+	if (PX4_OK != ret) {
+		_sensor_ok = false;
+		DEVICE_DEBUG("measure error");
+	}
+
+	// schedule a fresh cycle call when the measurement is done
+	work_queue(HPWORK, &_work, (worker_t)&Airspeed::cycle_trampoline, this, USEC2TICK(CONVERSION_INTERVAL));
+}
+
+bool SDP3X::crc(const uint8_t data[], unsigned size, uint8_t checksum)
+{
+	uint8_t crc = 0xff;
+
+	// calculate 8-bit checksum with polynomial 0x31 (x^8 + x^5 + x^4 + 1)
+	for (unsigned i = 0; i < size; i++) {
+		crc ^= (data[i]);
+
+		for (int bit = 8; bit > 0; --bit) {
+			if (crc & 0x80) {
+				crc = (crc << 1) ^ 0x31;
+
+			} else {
+				crc = (crc << 1);
+			}
+		}
+	}
+
+	// verify checksum
+	return (crc == checksum);
+}

src/drivers/sdp3x_airspeed/SDP3X.hpp

@@ -0,0 +1,110 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2017 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file SDP3X.hpp
+ *
+ * Driver for Sensirion SDP3X Differential Pressure Sensor
+ *
+ * Datasheet: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/8_Differential_Pressure/Sensirion_Differential_Pressure_Sensors_SDP3x_Digital_Datasheet_V0.8.pdf
+ */
+
+#ifndef DRIVERS_SDP3X_AIRSPEED_HPP_
+#define DRIVERS_SDP3X_AIRSPEED_HPP_
+
+#include <drivers/airspeed/airspeed.h>
+#include <drivers/device/i2c.h>
+#include <drivers/drv_airspeed.h>
+#include <math.h>
+#include <mathlib/math/filter/LowPassFilter2p.hpp>
+#include <px4_config.h>
+#include <sys/types.h>
+#include <systemlib/airspeed.h>
+#include <systemlib/perf_counter.h>
+#include <uORB/topics/differential_pressure.h>
+#include <uORB/uORB.h>
+
+#define I2C_ADDRESS_1_SDP3X		0x21
+#define I2C_ADDRESS_2_SDP3X		0x22
+#define I2C_ADDRESS_3_SDP3X		0x23
+
+#define SDP3X_SCALE_TEMPERATURE		200.0f
+#define SDP3X_RESET_ADDR		0x00
+#define SDP3X_RESET_CMD			0x06
+#define SDP3X_CONT_MEAS_AVG_MODE	0x3615
+
+#define PATH_SDP3X "/dev/sdp3x"
+
+// Measurement rate is 20Hz
+#define SPD3X_MEAS_RATE 100
+#define SDP3X_MEAS_DRIVER_FILTER_FREQ 1.5f
+#define CONVERSION_INTERVAL	(1000000 / SPD3X_MEAS_RATE)	/* microseconds */
+
+class SDP3X : public Airspeed
+{
+public:
+	SDP3X(int bus, int address = I2C_ADDRESS_1_SDP3X, const char *path = PATH_SDP3X) :
+		Airspeed(bus, address, CONVERSION_INTERVAL, path)
+	{
+	}
+
+private:
+
+	/**
+	 * Perform a poll cycle; collect from the previous measurement
+	 * and start a new one.
+	 */
+	void	cycle() override;
+	int	measure() override { return 0; }
+	int	collect() override;
+	int	probe() override;
+
+	math::LowPassFilter2p _filter{SPD3X_MEAS_RATE, SDP3X_MEAS_DRIVER_FILTER_FREQ};
+
+	bool init_sdp3x();
+
+	/**
+	 * Calculate the CRC8 for the sensor payload data
+	 */
+	bool crc(const uint8_t data[], unsigned size, uint8_t checksum);
+
+	/**
+	 * Write a command in Sensirion specific logic
+	 */
+	int write_command(uint16_t command);
+
+	bool _inited{false};
+	int16_t _scale{0};
+};
+
+#endif /* DRIVERS_SDP3X_AIRSPEED_HPP_ */

src/drivers/sdp3x_airspeed/SDP3X_main.cpp

@@ -0,0 +1,289 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2017 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#include "SDP3X.hpp"
+
+// Driver 'main' command.
+extern "C" __EXPORT int sdp3x_airspeed_main(int argc, char *argv[]);
+
+// Local functions in support of the shell command.
+namespace sdp3x_airspeed
+{
+SDP3X *g_dev = nullptr;
+
+void start(int i2c_bus);
+void stop();
+void test();
+void reset();
+void info();
+
+// Start the driver.
+// This function call only returns once the driver is up and running
+// or failed to detect the sensor.
+void
+start(int i2c_bus)
+{
+	int fd = -1;
+
+	if (g_dev != nullptr) {
+		errx(1, "already started");
+	}
+
+	g_dev = new SDP3X(i2c_bus, I2C_ADDRESS_1_SDP3X, PATH_SDP3X);
+
+	/* check if the MS4525DO was instantiated */
+	if (g_dev == nullptr) {
+		goto fail;
+	}
+
+	/* try the next SDP3XDSO if init fails */
+	if (OK != g_dev->Airspeed::init()) {
+		delete g_dev;
+
+		PX4_WARN("trying SDP3X 2");
+
+		g_dev = new SDP3X(i2c_bus, I2C_ADDRESS_2_SDP3X, PATH_SDP3X);
+
+		/* check if the SDP3XDSO was instantiated */
+		if (g_dev == nullptr) {
+			PX4_WARN("SDP3X was not instantiated");
+			goto fail;
+		}
+
+		/* both versions failed if the init for the SDP3XDSO fails, give up */
+		if (OK != g_dev->Airspeed::init()) {
+			PX4_WARN("SDP3X init fail");
+			goto fail;
+		}
+	}
+
+	/* set the poll rate to default, starts automatic data collection */
+	fd = open(PATH_SDP3X, O_RDONLY);
+
+	if (fd < 0) {
+		goto fail;
+	}
+
+	if (ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) {
+		goto fail;
+	}
+
+	exit(0);
+
+fail:
+
+	if (g_dev != nullptr) {
+		delete g_dev;
+		g_dev = nullptr;
+	}
+
+	PX4_WARN("no SDP3X airspeed sensor connected");
+	exit(1);
+}
+
+// stop the driver
+void stop()
+{
+	if (g_dev != nullptr) {
+		delete g_dev;
+		g_dev = nullptr;
+
+	} else {
+		errx(1, "driver not running");
+	}
+
+	exit(0);
+}
+
+// perform some basic functional tests on the driver;
+// make sure we can collect data from the sensor in polled
+// and automatic modes.
+void test()
+{
+	int fd = open(PATH_SDP3X, O_RDONLY);
+
+	if (fd < 0) {
+		PX4_WARN("%s open failed (try 'sdp3x_airspeed start' if the driver is not running", PATH_SDP3X);
+		exit(1);
+	}
+
+	// do a simple demand read
+	differential_pressure_s report;
+	ssize_t sz = read(fd, &report, sizeof(report));
+
+	if (sz != sizeof(report)) {
+		PX4_WARN("immediate read failed");
+		exit(1);
+	}
+
+	PX4_WARN("single read");
+	PX4_WARN("diff pressure: %d pa", (int)report.differential_pressure_filtered_pa);
+
+	/* start the sensor polling at 2Hz */
+	if (OK != ioctl(fd, SENSORIOCSPOLLRATE, 2)) {
+		PX4_WARN("failed to set 2Hz poll rate");
+		exit(1);
+	}
+
+	/* read the sensor 5x and report each value */
+	for (unsigned i = 0; i < 5; i++) {
+		struct pollfd fds;
+
+		/* wait for data to be ready */
+		fds.fd = fd;
+		fds.events = POLLIN;
+		int ret = poll(&fds, 1, 2000);
+
+		if (ret != 1) {
+			errx(1, "timed out");
+		}
+
+		/* now go get it */
+		sz = read(fd, &report, sizeof(report));
+
+		if (sz != sizeof(report)) {
+			err(1, "periodic read failed");
+		}
+
+		PX4_WARN("periodic read %u", i);
+		PX4_WARN("diff pressure: %d pa", (int)report.differential_pressure_filtered_pa);
+		PX4_WARN("temperature: %d C (0x%02x)", (int)report.temperature, (unsigned) report.temperature);
+	}
+
+	/* reset the sensor polling to its default rate */
+	if (PX4_OK != ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT)) {
+		PX4_WARN("failed to set default rate");
+		exit(1);
+	}
+
+	exit(0);
+}
+
+// reset the driver
+void reset()
+{
+	int fd = open(PATH_SDP3X, O_RDONLY);
+
+	if (fd < 0) {
+		err(1, "failed ");
+	}
+
+	if (ioctl(fd, SENSORIOCRESET, 0) < 0) {
+		err(1, "driver reset failed");
+	}
+
+	if (ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) {
+		err(1, "driver poll restart failed");
+	}
+
+	exit(0);
+}
+
+// print a little info about the driver
+void
+info()
+{
+	if (g_dev == nullptr) {
+		errx(1, "driver not running");
+	}
+
+	printf("state @ %p\n", g_dev);
+	g_dev->print_info();
+
+	exit(0);
+}
+
+} // namespace sdp3x_airspeed
+
+
+static void
+sdp3x_airspeed_usage()
+{
+	PX4_WARN("usage: sdp3x_airspeed command [options]");
+	PX4_WARN("options:");
+	PX4_WARN("\t-b --bus i2cbus (%d)", PX4_I2C_BUS_DEFAULT);
+	PX4_WARN("command:");
+	PX4_WARN("\tstart|stop|reset|test|info");
+}
+
+int
+sdp3x_airspeed_main(int argc, char *argv[])
+{
+	int i2c_bus = PX4_I2C_BUS_DEFAULT;
+
+	for (int i = 1; i < argc; i++) {
+		if (strcmp(argv[i], "-b") == 0 || strcmp(argv[i], "--bus") == 0) {
+			if (argc > i + 1) {
+				i2c_bus = atoi(argv[i + 1]);
+			}
+		}
+	}
+
+	/*
+	 * Start/load the driver.
+	 */
+	if (!strcmp(argv[1], "start")) {
+		sdp3x_airspeed::start(i2c_bus);
+	}
+
+	/*
+	 * Stop the driver
+	 */
+	if (!strcmp(argv[1], "stop")) {
+		sdp3x_airspeed::stop();
+	}
+
+	/*
+	 * Test the driver/device.
+	 */
+	if (!strcmp(argv[1], "test")) {
+		sdp3x_airspeed::test();
+	}
+
+	/*
+	 * Reset the driver.
+	 */
+	if (!strcmp(argv[1], "reset")) {
+		sdp3x_airspeed::reset();
+	}
+
+	/*
+	 * Print driver information.
+	 */
+	if (!strcmp(argv[1], "info") || !strcmp(argv[1], "status")) {
+		sdp3x_airspeed::info();
+	}
+
+	sdp3x_airspeed_usage();
+	exit(0);
+}