ardupilot/libraries/AP_Airspeed/AP_Airspeed_DLVR.cpp

/*
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "AP_Airspeed_DLVR.h"
#include <AP_Math/AP_Math.h>

extern const AP_HAL::HAL &hal;

#define DLVR_I2C_ADDR 0x28

#ifdef DLVR_DEBUGGING
 # define Debug(fmt, args ...)  do {hal.console->printf("%s:%d: " fmt "\n", __FUNCTION__, __LINE__, ## args); hal.scheduler->delay(1); } while(0)
#else
 # define Debug(fmt, args ...)
#endif


AP_Airspeed_DLVR::AP_Airspeed_DLVR(AP_Airspeed &_frontend, uint8_t _instance) :
    AP_Airspeed_Backend(_frontend, _instance)
{}

// probe and initialise the sensor
bool AP_Airspeed_DLVR::init()
{
    dev = hal.i2c_mgr->get_device(get_bus(), DLVR_I2C_ADDR);
    if (!dev) {
        return false;
    }
    dev->get_semaphore()->take_blocking();
    dev->set_speed(AP_HAL::Device::SPEED_LOW);
    dev->set_retries(2);
    dev->get_semaphore()->give();
    dev->register_periodic_callback(1000000UL/50U,
                                    FUNCTOR_BIND_MEMBER(&AP_Airspeed_DLVR::timer, void));
    return true;
}

#define STATUS_SHIFT 30
#define TEMPERATURE_SHIFT 5
#define TEMPERATURE_MASK ((1 << 11) - 1)
#define PRESSURE_SHIFT 16
#define PRESSURE_MASK ((1 << 14) - 1)

#define DLVR_FSS       5.0f // assumes 5 inch H2O sensor
#define DLVR_OFFSET 8192.0f
#define DLVR_SCALE 16384.0f

// 50Hz timer
void AP_Airspeed_DLVR::timer()
{
    uint8_t raw_bytes[4];
    if (!dev->read((uint8_t *)&raw_bytes, sizeof(raw_bytes))) {
        return;
    }

    uint32_t data = (raw_bytes[0] << 24) |
                    (raw_bytes[1] << 16) |
                    (raw_bytes[2] << 8)  |
                    raw_bytes[3];

    if ((data >> STATUS_SHIFT)) {
        // anything other then 00 in the status bits is an error
        Debug("DLVR: Bad status read %d", data >> STATUS_SHIFT);
        return;
    }

    uint32_t pres_raw = (data >> PRESSURE_SHIFT)    & PRESSURE_MASK;
    uint32_t temp_raw = (data >> TEMPERATURE_SHIFT) & TEMPERATURE_MASK;

    float press_h2o = 1.25f * 2.0f * DLVR_FSS * ((pres_raw - DLVR_OFFSET) / DLVR_SCALE);
    float temp = temp_raw * (200.0f / 2047.0f) - 50.0f;

    sem->take_blocking();
    pressure_sum += INCH_OF_H2O_TO_PASCAL * press_h2o;
    temperature_sum += temp;
    press_count++;
    temp_count++;
    last_sample_time_ms = AP_HAL::millis();
    sem->give();
}

// return the current differential_pressure in Pascal
bool AP_Airspeed_DLVR::get_differential_pressure(float &_pressure)
{
    if ((AP_HAL::millis() - last_sample_time_ms) > 100) {
        return false;
    }
    if (sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        if (press_count > 0) {
            pressure = pressure_sum / press_count;
            press_count = 0;
            pressure_sum = 0;
        }
        sem->give();
    }
    _pressure = pressure;
    return true;
}

// return the current temperature in degrees C, if available
bool AP_Airspeed_DLVR::get_temperature(float &_temperature)
{
    if ((AP_HAL::millis() - last_sample_time_ms) > 100) {
        return false;
    }
    if (sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        if (temp_count > 0) {
            temperature = temperature_sum / temp_count;
            temp_count = 0;
            temperature_sum = 0;
        }
        sem->give();
    }
    _temperature = temperature;
    return true;
}