ardupilot/libraries/AP_Baro/AP_Baro_PX4.cpp

/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-

#include <AP_HAL.h>

#if CONFIG_HAL_BOARD == HAL_BOARD_PX4
#include <AP_Baro.h>
#include "AP_Baro_PX4.h"

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

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

extern const AP_HAL::HAL& hal;

// Public Methods //////////////////////////////////////////////////////////////
bool AP_Baro_PX4::init(void)
{
    if (_baro_fd <= 0) {
        _baro_fd = open(BARO_DEVICE_PATH, O_RDONLY);
        if (_baro_fd < 0) {
            hal.scheduler->panic("Unable to open " BARO_DEVICE_PATH);
        }

        /* set the driver to poll at 150Hz */
        ioctl(_baro_fd, SENSORIOCSPOLLRATE, SENSOR_POLLRATE_MAX);

        // average over up to 20 samples
        ioctl(_baro_fd, SENSORIOCSQUEUEDEPTH, 20);

        // give the timer a chance to run and gather one sample
        hal.scheduler->delay(40);
        _accumulate();
    }

    return true;
}

// Read the sensor
uint8_t AP_Baro_PX4::read(void)
{
    // try to accumulate one more sample, so we have the latest data
    _accumulate();

    // consider the baro healthy if we got a reading in the last 0.2s
    healthy = (hrt_absolute_time() - _last_timestamp < 200000);
    if (!healthy || _sum_count == 0) {
        return healthy;
    }

    _pressure    = (_pressure_sum / _sum_count) * 100.0f;
    _temperature = _temperature_sum / _sum_count;
    _pressure_samples = _sum_count;
    _last_update = (uint32_t)_last_timestamp/1000;
    _pressure_sum = 0;
    _temperature_sum = 0;
    _sum_count = 0;

    return 1;
}

// accumulate sensor values
void AP_Baro_PX4::_accumulate(void)
{
    struct baro_report baro_report;
    while (::read(_baro_fd, &baro_report, sizeof(baro_report)) == sizeof(baro_report) &&
           baro_report.timestamp != _last_timestamp) {
		_pressure_sum += baro_report.pressure; // Pressure in mbar
		_temperature_sum += baro_report.temperature; // degrees celcius
        _sum_count++;
        _last_timestamp = baro_report.timestamp;
    }
}

float AP_Baro_PX4::get_pressure() {
    return _pressure;
}

float AP_Baro_PX4::get_temperature() {
    return _temperature;
}

#endif // CONFIG_HAL_BOARD