path: root/src/drivers/meas_airspeed/meas_airspeed.cpp

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/**
 * @file meas_airspeed.cpp
 * @author Lorenz Meier
 * @author Sarthak Kaingade
 * @author Simon Wilks
 * @author Thomas Gubler
 *
 * Driver for the MEAS Spec series connected via I2C.
 *
 * Supported sensors:
 *
 *    - MS4525DO (http://www.meas-spec.com/downloads/MS4525DO.pdf)
 *    - untested: MS5525DSO (http://www.meas-spec.com/downloads/MS5525DSO.pdf)
 *
 * Interface application notes:
 *
 *    - Interfacing to MEAS Digital Pressure Modules (http://www.meas-spec.com/downloads/Interfacing_to_MEAS_Digital_Pressure_Modules.pdf)
 */


#include <nuttx/config.h>

#include <drivers/device/i2c.h>

#include <sys/types.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdbool.h>
#include <semaphore.h>
#include <string.h>
#include <fcntl.h>
#include <poll.h>
#include <errno.h>
#include <stdio.h>
#include <math.h>
#include <unistd.h>

#include <nuttx/arch.h>
#include <nuttx/wqueue.h>
#include <nuttx/clock.h>

#include <board_config.h>

#include <systemlib/airspeed.h>
#include <systemlib/err.h>
#include <systemlib/param/param.h>
#include <systemlib/perf_counter.h>

#include <mathlib/math/filter/LowPassFilter2p.hpp>

#include <drivers/drv_airspeed.h>
#include <drivers/drv_hrt.h>

#include <uORB/uORB.h>
#include <uORB/topics/differential_pressure.h>
#include <uORB/topics/subsystem_info.h>
#include <uORB/topics/system_power.h>

#include <drivers/airspeed/airspeed.h>

/* I2C bus address is 1010001x */
#define I2C_ADDRESS_MS4525DO	0x28	//0x51 /* 7-bit address. */
#define PATH_MS4525		"/dev/ms4525"
/* The MS5525DSO address is 111011Cx, where C is the complementary value of the pin CSB */
#define I2C_ADDRESS_MS5525DSO	0x77	//0x77/* 7-bit address, addr. pin pulled low */
#define PATH_MS5525		"/dev/ms5525"

/* Register address */
#define ADDR_READ_MR			0x00	/* write to this address to start conversion */

/* Measurement rate is 100Hz */
#define MEAS_RATE 100.0f
#define MEAS_DRIVER_FILTER_FREQ 3.0f
#define CONVERSION_INTERVAL	(1000000 / 100)	/* microseconds */

class MEASAirspeed : public Airspeed
{
public:
	MEASAirspeed(int bus, int address = I2C_ADDRESS_MS4525DO, const char *path = PATH_MS4525);

protected:

	/**
	* Perform a poll cycle; collect from the previous measurement
	* and start a new one.
	*/
	virtual void	cycle();
	virtual int	measure();
	virtual int	collect();

	math::LowPassFilter2p	_filter;

	/**
	 * Correct for 5V rail voltage variations
	 */
	void voltage_correction(float &diff_pres_pa, float &temperature);

	int _t_system_power;
	struct system_power_s system_power;
};

/*
 * Driver 'main' command.
 */
extern "C" __EXPORT int meas_airspeed_main(int argc, char *argv[]);

MEASAirspeed::MEASAirspeed(int bus, int address, const char *path) : Airspeed(bus, address,
	CONVERSION_INTERVAL, path),
	_filter(MEAS_RATE, MEAS_DRIVER_FILTER_FREQ),
	_t_system_power(-1)
{
	memset(&system_power, 0, sizeof(system_power));
}

int
MEASAirspeed::measure()
{
	int ret;

	/*
	 * Send the command to begin a measurement.
	 */
	uint8_t cmd = 0;
	ret = transfer(&cmd, 1, nullptr, 0);

	if (OK != ret) {
		perf_count(_comms_errors);
	}

	return ret;
}

int
MEASAirspeed::collect()
{
	int	ret = -EIO;

	/* read from the sensor */
	uint8_t val[4] = {0, 0, 0, 0};


	perf_begin(_sample_perf);

	ret = transfer(nullptr, 0, &val[0], 4);

	if (ret < 0) {
		perf_count(_comms_errors);
		perf_end(_sample_perf);
		return ret;
	}

	uint8_t status = (val[0] & 0xC0) >> 6;

	switch (status) {
	case 0:
		break;

	case 1:
		/* fallthrough */
	case 2:
		/* fallthrough */
	case 3:
		perf_count(_comms_errors);
		perf_end(_sample_perf);
		return -EAGAIN;
	}

	int16_t dp_raw = 0, dT_raw = 0;
	dp_raw = (val[0] << 8) + val[1];
	/* mask the used bits */
	dp_raw = 0x3FFF & dp_raw;
	dT_raw = (val[2] << 8) + val[3];
	dT_raw = (0xFFE0 & dT_raw) >> 5;
	float temperature = ((200.0f * dT_raw) / 2047) - 50;

	// Calculate differential pressure. As its centered around 8000
	// and can go positive or negative
	const float P_min = -1.0f;
	const float P_max = 1.0f;
	const float PSI_to_Pa = 6894.757f;
	/*
	  this equation is an inversion of the equation in the
	  pressure transfer function figure on page 4 of the datasheet

	  We negate the result so that positive differential pressures
	  are generated when the bottom port is used as the static
	  port on the pitot and top port is used as the dynamic port
	 */
	float diff_press_PSI = -((dp_raw - 0.1f*16383) * (P_max-P_min)/(0.8f*16383) + P_min);
	float diff_press_pa_raw = diff_press_PSI * PSI_to_Pa;

        // correct for 5V rail voltage if possible
        voltage_correction(diff_press_pa_raw, temperature);

	// the raw value still should be compensated for the known offset
	diff_press_pa_raw -= _diff_pres_offset;

	float diff_press_pa = fabsf(diff_press_pa_raw);
	
	/*
	  note that we return both the absolute value with offset
	  applied and a raw value without the offset applied. This
	  makes it possible for higher level code to detect if the
	  user has the tubes connected backwards, and also makes it
	  possible to correctly use offsets calculated by a higher
	  level airspeed driver.

	  With the above calculation the MS4525 sensor will produce a
	  positive number when the top port is used as a dynamic port
	  and bottom port is used as the static port

	  Also note that the _diff_pres_offset is applied before the
	  fabsf() not afterwards. It needs to be done this way to
	  prevent a bias at low speeds, but this also means that when
	  setting a offset you must set it based on the raw value, not
	  the offset value
	 */
	
	struct differential_pressure_s report;

	/* track maximum differential pressure measured (so we can work out top speed). */
	if (diff_press_pa > _max_differential_pressure_pa) {
		_max_differential_pressure_pa = diff_press_pa;
	}

	report.timestamp = hrt_absolute_time();
	report.error_count = perf_event_count(_comms_errors);
	report.temperature = temperature;
	report.differential_pressure_pa = diff_press_pa;
	report.differential_pressure_filtered_pa =  _filter.apply(diff_press_pa);

	/* the dynamics of the filter can make it overshoot into the negative range */
	if (report.differential_pressure_filtered_pa < 0.0f) {
		report.differential_pressure_filtered_pa = _filter.reset(diff_press_pa);
	}

	report.differential_pressure_raw_pa = diff_press_pa_raw;
	report.max_differential_pressure_pa = _max_differential_pressure_pa;

	if (_airspeed_pub > 0 && !(_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
MEASAirspeed::cycle()
{
	int ret;

	/* collection phase? */
	if (_collect_phase) {

		/* perform collection */
		ret = collect();
		if (OK != ret) {
			/* restart the measurement state machine */
			start();
			_sensor_ok = false;
			return;
		}

		/* next phase is measurement */
		_collect_phase = false;

		/*
		 * Is there a collect->measure gap?
		 */
		if (_measure_ticks > USEC2TICK(CONVERSION_INTERVAL)) {

			/* schedule a fresh cycle call when we are ready to measure again */
			work_queue(HPWORK,
				   &_work,
				   (worker_t)&Airspeed::cycle_trampoline,
				   this,
				   _measure_ticks - USEC2TICK(CONVERSION_INTERVAL));

			return;
		}
	}

	/* measurement phase */
	ret = measure();
	if (OK != ret) {
		debug("measure error");
	}

	_sensor_ok = (ret == OK);

	/* next phase is collection */
	_collect_phase = true;

	/* schedule a fresh cycle call when the measurement is done */
	work_queue(HPWORK,
		   &_work,
		   (worker_t)&Airspeed::cycle_trampoline,
		   this,
		   USEC2TICK(CONVERSION_INTERVAL));
}

/**
   correct for 5V rail voltage if the system_power ORB topic is
   available
   
   See http://uav.tridgell.net/MS4525/MS4525-offset.png for a graph of
   offset versus voltage for 3 sensors
 */
void
MEASAirspeed::voltage_correction(float &diff_press_pa, float &temperature)
{
#ifdef CONFIG_ARCH_BOARD_PX4FMU_V2
	if (_t_system_power == -1) {
		_t_system_power = orb_subscribe(ORB_ID(system_power));
	}
	if (_t_system_power == -1) {
		// not available
		return;
	}
	bool updated = false;
	orb_check(_t_system_power, &updated);
	if (updated) {
		orb_copy(ORB_ID(system_power), _t_system_power, &system_power);
	}
	if (system_power.voltage5V_v < 3.0f || system_power.voltage5V_v > 6.0f) {
		// not valid, skip correction
		return;
	}

	const float slope = 65.0f;
	/*
	  apply a piecewise linear correction, flattening at 0.5V from 5V
	 */
	float voltage_diff = system_power.voltage5V_v - 5.0f;
	if (voltage_diff > 0.5f) {
		voltage_diff = 0.5f;
	}
	if (voltage_diff < -0.5f) {
		voltage_diff = -0.5f;
	}
	diff_press_pa -= voltage_diff * slope;

	/*
	  the temperature masurement varies as well
	 */
	const float temp_slope = 0.887f;
	voltage_diff = system_power.voltage5V_v - 5.0f;
	if (voltage_diff > 0.5f) {
		voltage_diff = 0.5f;
	}
	if (voltage_diff < -1.0f) {
		voltage_diff = -1.0f;
	}
	temperature -= voltage_diff * temp_slope;	
#endif // CONFIG_ARCH_BOARD_PX4FMU_V2
}

/**
 * Local functions in support of the shell command.
 */
namespace meas_airspeed
{

/* oddly, ERROR is not defined for c++ */
#ifdef ERROR
# undef ERROR
#endif
const int ERROR = -1;

MEASAirspeed	*g_dev = nullptr;

void	start(int i2c_bus);
void	stop();
void	test();
void	reset();
void	info();

/**
 * Start the driver.
 */
void
start(int i2c_bus)
{
	int fd;

	if (g_dev != nullptr) {
		errx(1, "already started");
	}

	/* create the driver, try the MS4525DO first */
	g_dev = new MEASAirspeed(i2c_bus, I2C_ADDRESS_MS4525DO, PATH_MS4525);

	/* check if the MS4525DO was instantiated */
	if (g_dev == nullptr) {
		goto fail;
	}

	/* try the MS5525DSO next if init fails */
	if (OK != g_dev->Airspeed::init()) {
		delete g_dev;
		g_dev = new MEASAirspeed(i2c_bus, I2C_ADDRESS_MS5525DSO, PATH_MS5525);

		/* check if the MS5525DSO was instantiated */
		if (g_dev == nullptr) {
			goto fail;
		}

		/* both versions failed if the init for the MS5525DSO fails, give up */
		if (OK != g_dev->Airspeed::init()) {
			goto fail;
		}
	}

	/* set the poll rate to default, starts automatic data collection */
	fd = open(AIRSPEED_DEVICE_PATH, 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;
	}

	errx(1, "no MS4525 airspeed sensor connected");
}

/**
 * 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()
{
	struct differential_pressure_s report;
	ssize_t sz;
	int ret;

	int fd = open(AIRSPEED_DEVICE_PATH, O_RDONLY);

	if (fd < 0) {
		err(1, "%s open failed (try 'meas_airspeed start' if the driver is not running", AIRSPEED_DEVICE_PATH);
	}

	/* do a simple demand read */
	sz = read(fd, &report, sizeof(report));

	if (sz != sizeof(report)) {
		err(1, "immediate read failed");
	}

	warnx("single read");
	warnx("diff pressure: %d pa", (int)report.differential_pressure_pa);

	/* start the sensor polling at 2Hz */
	if (OK != ioctl(fd, SENSORIOCSPOLLRATE, 2)) {
		errx(1, "failed to set 2Hz poll rate");
	}

	/* 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;
		ret = poll(&fds, 1, 2000);

		if (ret != 1) {
			errx(1, "timed out waiting for sensor data");
		}

		/* now go get it */
		sz = read(fd, &report, sizeof(report));

		if (sz != sizeof(report)) {
			err(1, "periodic read failed");
		}

		warnx("periodic read %u", i);
		warnx("diff pressure: %d pa", (int)report.differential_pressure_pa);
		warnx("temperature: %d C (0x%02x)", (int)report.temperature, (unsigned) report.temperature);
	}

	/* reset the sensor polling to its default rate */
	if (OK != ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT)) {
		errx(1, "failed to set default rate");
	}

	errx(0, "PASS");
}

/**
 * Reset the driver.
 */
void
reset()
{
	int fd = open(AIRSPEED_DEVICE_PATH, 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


static void
meas_airspeed_usage()
{
	warnx("usage: meas_airspeed command [options]");
	warnx("options:");
	warnx("\t-b --bus i2cbus (%d)", PX4_I2C_BUS_DEFAULT);
	warnx("command:");
	warnx("\tstart|stop|reset|test|info");
}

int
meas_airspeed_main(int argc, char *argv[])
{
	int i2c_bus = PX4_I2C_BUS_DEFAULT;

	int i;

	for (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")) {
		meas_airspeed::start(i2c_bus);
	}

	/*
	 * Stop the driver
	 */
	if (!strcmp(argv[1], "stop")) {
		meas_airspeed::stop();
	}

	/*
	 * Test the driver/device.
	 */
	if (!strcmp(argv[1], "test")) {
		meas_airspeed::test();
	}

	/*
	 * Reset the driver.
	 */
	if (!strcmp(argv[1], "reset")) {
		meas_airspeed::reset();
	}

	/*
	 * Print driver information.
	 */
	if (!strcmp(argv[1], "info") || !strcmp(argv[1], "status")) {
		meas_airspeed::info();
	}

	meas_airspeed_usage();
	exit(0);
}