ms4525_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)
 *
 * Interface application notes:
 *
 *    - Interfacing to MEAS Digital Pressure Modules (http://www.meas-spec.com/downloads/Interfacing_to_MEAS_Digital_Pressure_Modules.pdf)
 */

#include <mathlib/math/filter/LowPassFilter2p.hpp>
#include <px4_platform_common/getopt.h>
#include <uORB/topics/system_power.h>

#include <drivers/airspeed/airspeed.h>

enum MS_DEVICE_TYPE {
    DEVICE_TYPE_MS4515  = 4515,
    DEVICE_TYPE_MS4525  = 4525
};

/* I2C bus address is 1010001x */
#define I2C_ADDRESS_MS4515DO    0x46
#define I2C_ADDRESS_MS4525DO    0x28    /**< 7-bit address. Depends on the order code (this is for code "I") */
#define PATH_MS4525     "/dev/ms4525"

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

/* Measurement rate is 100Hz */
#define MEAS_RATE 100
#define MEAS_DRIVER_FILTER_FREQ 1.2f
#define CONVERSION_INTERVAL (1000000 / MEAS_RATE)   /* 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.
    */
    void    Run() override;
    int measure() override;
    int collect() override;

    math::LowPassFilter2p   _filter{MEAS_RATE, MEAS_DRIVER_FILTER_FREQ};

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

    int _t_system_power{-1};
    system_power_s system_power{};
};

/*
 * Driver 'main' command.
 */
extern "C" __EXPORT int ms4525_airspeed_main(int argc, char *argv[]);

MEASAirspeed::MEASAirspeed(int bus, int address, const char *path) : Airspeed(bus, address, CONVERSION_INTERVAL, path)
{
    _device_id.devid_s.devtype = DRV_DIFF_PRESS_DEVTYPE_MS4525;
}

int
MEASAirspeed::measure()
{
    // Send the command to begin a measurement.
    uint8_t cmd = 0;
    int ret = transfer(&cmd, 1, nullptr, 0);

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

    return ret;
}

int
MEASAirspeed::collect()
{
    /* read from the sensor */
    uint8_t val[4] = {0, 0, 0, 0};

    perf_begin(_sample_perf);

    int 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:
        // Normal Operation. Good Data Packet
        break;

    case 1:
        // Reserved
        return -EAGAIN;

    case 2:
        // Stale Data. Data has been fetched since last measurement cycle.
        return -EAGAIN;

    case 3:
        // Fault Detected
        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;

    // dT max is almost certainly an invalid reading
    if (dT_raw == 2047) {
        perf_count(_comms_errors);
        return -EAGAIN;
    }

    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);

    /*
      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
     */

    struct differential_pressure_s report;

    report.timestamp = hrt_absolute_time();
    report.error_count = perf_event_count(_comms_errors);
    report.temperature = temperature;
    report.differential_pressure_filtered_pa =  _filter.apply(diff_press_pa_raw) - _diff_pres_offset;
    report.differential_pressure_raw_pa = diff_press_pa_raw - _diff_pres_offset;
    report.device_id = _device_id.devid;

    if (_airspeed_pub != nullptr && !(_pub_blocked)) {
        /* publish it */
        orb_publish(ORB_ID(differential_pressure), _airspeed_pub, &report);
    }

    ret = OK;

    perf_end(_sample_perf);

    return ret;
}

void
MEASAirspeed::Run()
{
    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_interval > CONVERSION_INTERVAL) {

            /* schedule a fresh cycle call when we are ready to measure again */
            ScheduleDelayed(_measure_interval - CONVERSION_INTERVAL);

            return;
        }
    }

    /* measurement phase */
    ret = measure();

    if (OK != ret) {
        DEVICE_DEBUG("measure error");
    }

    _sensor_ok = (ret == OK);

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

    /* schedule a fresh cycle call when the measurement is done */
    ScheduleDelayed(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)
{
#if defined(ADC_SCALED_V5_SENSE)

    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 // defined(ADC_SCALED_V5_SENSE)
}

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

MEASAirspeed    *g_dev = nullptr;

int start();
int start_bus(int i2c_bus, int address);
int stop();
int reset();

/**
* Attempt to start driver on all available I2C busses.
*
* This function will return as soon as the first sensor
* is detected on one of the available busses or if no
* sensors are detected.
*
*/
int
start()
{
    for (unsigned i = 0; i < NUM_I2C_BUS_OPTIONS; i++) {
        if (start_bus(i2c_bus_options[i], I2C_ADDRESS_MS4525DO) == PX4_OK) {
            return PX4_OK;
        }
    }

    return PX4_ERROR;

}

/**
 * Start the driver on a specific bus.
 *
 * This function call only returns once the driver is up and running
 * or failed to detect the sensor.
 */
int
start_bus(int i2c_bus, int address)
{
    int fd;

    if (g_dev != nullptr) {
        PX4_ERR("already started");
        return PX4_ERROR;
    }

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

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

    if (OK != g_dev->init()) {
        goto fail;
    }

    /* set the poll rate to default, starts automatic data collection */
    fd = px4_open(PATH_MS4525, O_RDONLY);

    if (fd < 0) {
        goto fail;
    }

    if (px4_ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) {
        goto fail;
    }

    return PX4_OK;

fail:

    if (g_dev != nullptr) {
        delete g_dev;
        g_dev = nullptr;
    }

    return PX4_ERROR;
}

/**
 * Stop the driver
 */
int
stop()
{
    if (g_dev != nullptr) {
        delete g_dev;
        g_dev = nullptr;

    } else {
        PX4_ERR("driver not running");
        return PX4_ERROR;
    }

    return PX4_OK;
}

/**
 * Reset the driver.
 */
int
reset()
{
    int fd = px4_open(PATH_MS4525, O_RDONLY);

    if (fd < 0) {
        PX4_ERR("failed");
        return PX4_ERROR;
    }

    if (px4_ioctl(fd, SENSORIOCRESET, 0) < 0) {
        PX4_ERR("driver reset failed");
        return PX4_ERROR;
    }

    if (px4_ioctl(fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_DEFAULT) < 0) {
        PX4_ERR("driver poll restart failed");
        return PX4_ERROR;
    }

    return PX4_OK;
}

} // namespace


static void
meas_airspeed_usage()
{
    PX4_INFO("usage: ms4525 command [options]");
    PX4_INFO("options:");
    PX4_INFO("\t-b --bus i2cbus (%d)", PX4_I2C_BUS_DEFAULT);
    PX4_INFO("\t-a --all");
    PX4_INFO("command:");
    PX4_INFO("\tstart|stop|reset");
}

int
ms4525_airspeed_main(int argc, char *argv[])
{
    int i2c_bus = PX4_I2C_BUS_DEFAULT;

    int myoptind = 1;
    int ch;
    const char *myoptarg = nullptr;

    int device_type = DEVICE_TYPE_MS4525;

    bool start_all = false;

    while ((ch = px4_getopt(argc, argv, "ab:T:", &myoptind, &myoptarg)) != EOF) {
        switch (ch) {
        case 'b':
            i2c_bus = atoi(myoptarg);
            break;

        case 'a':
            start_all = true;
            break;

        case 'T':
            device_type = atoi(myoptarg);
            break;

        default:
            meas_airspeed_usage();
            return 0;
        }
    }

    if (myoptind >= argc) {
        meas_airspeed_usage();
        return -1;
    }

    /*
     * Start/load the driver.
     */
    if (!strcmp(argv[myoptind], "start")) {
        if (start_all) {
            return meas_airspeed::start();

        } else if (device_type == DEVICE_TYPE_MS4515) {
            return meas_airspeed::start_bus(i2c_bus, I2C_ADDRESS_MS4515DO);

        } else if (device_type == DEVICE_TYPE_MS4525) {
            return meas_airspeed::start_bus(i2c_bus, I2C_ADDRESS_MS4525DO);
        }
    }

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

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

    meas_airspeed_usage();
    return 0;
}