ardupilot/libraries/AP_Baro/AP_Baro_KellerLD.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_Baro_KellerLD.h"

#if AP_BARO_KELLERLD_ENABLED

#include <stdio.h>

#include <AP_Math/AP_Math.h>

#define KELLER_DEBUG 0

#if KELLER_DEBUG
# define Debug(fmt, args ...)  do {printf(fmt "\n", ## args);} while(0)
#else
# define Debug(fmt, args ...)
#endif

extern const AP_HAL::HAL &hal;

// sensor metadata register
static const uint8_t CMD_METADATA_PMODE = 0x12;
// Measurement range registers
static const uint8_t CMD_PRANGE_MIN_MSB = 0x13;
static const uint8_t CMD_PRANGE_MIN_LSB = 0x14;
static const uint8_t CMD_PRANGE_MAX_MSB = 0x15;
static const uint8_t CMD_PRANGE_MAX_LSB = 0x16;

// write to this address to start pressure measurement
static const uint8_t CMD_REQUEST_MEASUREMENT = 0xAC;

// Status byte handling, per Keller LD "Communication Protocol 4LD-9LD" (v2.6, pg 7)
//   bits 7-6 : reserved, must be 01
//   bit 5    : ignored, known to be unreliable in block reads
//   bits 4-3 : operating mode (00 = normal measurement)
//   bit 2    : checksum error? (0 = ok, 1 = error)
//   bits 1-0 : don't care
static const uint8_t STATUS_REQUIRED_MASK = 0b11011100;
static const uint8_t STATUS_REQUIRED_BITS = 0b01000000;

AP_Baro_KellerLD::AP_Baro_KellerLD(AP_Baro &baro, AP_HAL::Device &dev)
    : AP_Baro_Backend(baro)
    , _dev(&dev)
{
}

// Look for the device on the bus and see if it responds appropriately
AP_Baro_Backend *AP_Baro_KellerLD::probe(AP_Baro &baro, AP_HAL::Device &dev)
{
    AP_Baro_KellerLD *sensor = NEW_NOTHROW AP_Baro_KellerLD(baro, dev);
    if (!sensor || !sensor->_init()) {
        delete sensor;
        return nullptr;
    }
    return sensor;
}


// convenience function to work around device transfer oddities
bool AP_Baro_KellerLD::transfer_with_delays(uint8_t *send, uint8_t sendlen, uint8_t *recv, uint8_t recvlen)
{
    if (!_dev->transfer(send, sendlen, nullptr, 0)) {
        return false;
    }
    hal.scheduler->delay(1);

    if(!_dev->transfer(nullptr, 0, recv, recvlen)) {
        return false;
    }
    hal.scheduler->delay(1);
    return true;
}

// This device has some undocumented finicky quirks and requires
// delays when reading out the measurement range, but for some reason
// this isn't an issue when requesting measurements.  This is why we
// need to split the transfers with delays like this.  (Using
// AP_HAL::I2CDevice::set_split_transfers will not work with these
// sensors)
bool AP_Baro_KellerLD::read_measurement_limit(float *limit, uint8_t msb_addr, uint8_t lsb_addr)
{
    uint8_t data[3];

    if (!transfer_with_delays(&msb_addr, 1, data, ARRAY_SIZE(data))) {
        return false;
    }

    const uint16_t ms_word = (data[1] << 8) | data[2];
    Debug("0x%02x: %d [%d, %d, %d]", msb_addr, ms_word, data[0], data[1], data[2]);

    if (!transfer_with_delays(&lsb_addr, 1, data, ARRAY_SIZE(data))) {
        return false;
    }

    const uint16_t ls_word = (data[1] << 8) | data[2];
    Debug("0x%02x: %d [%d, %d, %d]", lsb_addr, ls_word, data[0], data[1], data[2]);

    const uint32_t cal_data = (ms_word << 16) | ls_word;
    memcpy(limit, &cal_data, sizeof(*limit));

    if (isinf(*limit) || isnan(*limit)) {
        return false;
    }

    Debug("data: %d, float: %.2f", cal_data, _p_min);
    return true;
}

bool AP_Baro_KellerLD::read_cal()
{
    // Read out pressure measurement range
    if (!read_measurement_limit(&_p_min, CMD_PRANGE_MIN_MSB, CMD_PRANGE_MIN_LSB)) {
        return false;
    }

    if (!read_measurement_limit(&_p_max, CMD_PRANGE_MAX_MSB, CMD_PRANGE_MAX_LSB)) {
        return false;
    }

    if (_p_max <= _p_min) {
        return false;
    }

    return true;
}

// Read sensor P-Mode type and set pressure reference offset
// This determines the pressure offset based on the type of sensor
// vented to atmosphere, gauged to vacuum, or gauged to standard sea-level pressure
bool AP_Baro_KellerLD::read_mode_type()
{
    uint8_t cmd = CMD_METADATA_PMODE;
    uint8_t data[3];
    if (!transfer_with_delays(&cmd, 1, data, ARRAY_SIZE(data))) {
        return false;
    }

    // Byte 3, Bit 0 & 1: Represents P-Mode
    // "Communication Protocol 4 LD…9 LD", Version 2.6 pg 12 of 25
    // https://keller-druck.com/?d=VeMYAQBxgoSNjUSHbdnBTU
    _p_mode = (SensorMode)(data[2] & 0b11);

    // update pressure offset based on P-Mode
    switch (_p_mode) {
        case SensorMode::PR_MODE:
            // PR-Mode vented gauge sensor
            // pressure reads zero when the pressure outside is equal to the pressure inside the enclosure
            _p_mode_offset = _frontend.get_pressure(0);
            break;
        case SensorMode::PA_MODE:
            // PA-Mode sealed gauge sensor
            // pressure reads zero when the pressure outside is equal to 1.0 bar
            // i.e., the pressure at which the vent is sealed
            _p_mode_offset = 1.0;
            break;
        case SensorMode::PAA_MODE:
            // PAA-mode Absolute sensor (zero at vacuum)
            _p_mode_offset = 0.0;
            break;
        case SensorMode::UNDEFINED:
            // we should give an error here
            printf("KellerLD Device Mode UNDEFINED\n");
            return false;
    }

    return true;
}

// We read out the measurement range to be used in raw value conversions
bool AP_Baro_KellerLD::_init()
{
    if (!_dev) {
        return false;
    }

    WITH_SEMAPHORE(_dev->get_semaphore());

    // high retries for init
    _dev->set_retries(10);

    if (!read_cal()) {
        printf("Cal read bad!\n");
        return false;
    }

    if (!read_mode_type()) {
        printf("Mode_Type read bad!\n");
        return false;
    }

    printf("Keller LD found on bus %u address 0x%02x\n", _dev->bus_num(), _dev->get_bus_address());

    // Send a command to take a measurement
    _dev->transfer(&CMD_REQUEST_MEASUREMENT, 1, nullptr, 0);

    memset(&_accum, 0, sizeof(_accum));

    _instance = _frontend.register_sensor();

    _dev->set_device_type(DEVTYPE_BARO_KELLERLD);
    set_bus_id(_instance, _dev->get_bus_id());
    
    _frontend.set_type(_instance, AP_Baro::BARO_TYPE_WATER);

    // lower retries for run
    _dev->set_retries(3);

    // The sensor needs time to take a deep breath after reading out the calibration...
    hal.scheduler->delay(150);

    // Request 50Hz update
    // The sensor really struggles with any jitter in timing at 100Hz, and will sometimes start reading out all zeros
    _dev->register_periodic_callback(20 * AP_USEC_PER_MSEC,
                                     FUNCTOR_BIND_MEMBER(&AP_Baro_KellerLD::_timer, void));
    return true;
}

// Read out most recent measurement from sensor hw
bool AP_Baro_KellerLD::_read()
{
    uint8_t data[5];
    if (!_dev->transfer(nullptr, 0, data, sizeof(data))) {
        Debug("Keller LD read failed!");
        return false;
    }

    const uint8_t status = data[0];
    uint16_t pressure_raw = (data[1] << 8) | data[2];
    uint16_t temperature_raw = (data[3] << 8) | data[4];

#if KELLER_DEBUG
    static uint8_t samples = 0;
    if (samples < 3) {
        samples++;
        Debug("data: [%d, %d, %d, %d, %d]", data[0], data[1], data[2], data[3], data[4]);
        Debug("pressure_raw: %d\ttemperature_raw: %d", pressure_raw, temperature_raw);
    }
#endif

    // Reject if the sensor is not in the normal measurement state, or is reporting an error.
    if ((status & STATUS_REQUIRED_MASK) != STATUS_REQUIRED_BITS) {
        Debug("Keller: bad status 0x%02x", status);
        return false;
    }

    if (pressure_raw == 0 || temperature_raw == 0) {
        Debug("Keller: bad read");
        return false;
    }

    if (!pressure_ok(pressure_raw)) {
        return false;
    }
    
    WITH_SEMAPHORE(_sem);
    
    _update_and_wrap_accumulator(pressure_raw, temperature_raw, 128);
    
    return true;
}

// Periodic callback, regular update at 50Hz
// Read out most recent measurement, and request another
// Max conversion time according to datasheet is ~8ms, so
// max update rate is ~125Hz, yet we struggle to get consistent
// performance/data at 100Hz
void AP_Baro_KellerLD::_timer(void)
{
    _read();
    _dev->transfer(&CMD_REQUEST_MEASUREMENT, 1, nullptr, 0);
}

// Accumulate a reading, shrink if necessary to prevent overflow
void AP_Baro_KellerLD::_update_and_wrap_accumulator(uint16_t pressure, uint16_t temperature, uint8_t max_count)
{
    _accum.sum_pressure += pressure;
    _accum.sum_temperature += temperature;
    _accum.num_samples += 1;

    if (_accum.num_samples == max_count) {
        _accum.sum_pressure /= 2;
        _accum.sum_temperature /= 2;
        _accum.num_samples /= 2;
    }
}

// Take the average of accumulated values and push to frontend
void AP_Baro_KellerLD::update()
{
    float sum_pressure, sum_temperature;
    float num_samples;

    // update _p_mode_offset if vented guage 
    if (_p_mode == SensorMode::PR_MODE) {
        // we need to get the pressure from on-board barometer
        _p_mode_offset = _frontend.get_pressure(0);
    }

    {
        WITH_SEMAPHORE(_sem);

        if (_accum.num_samples == 0) {
            return;
        }

        sum_pressure = _accum.sum_pressure;
        sum_temperature = _accum.sum_temperature;
        num_samples = _accum.num_samples;
        memset(&_accum, 0, sizeof(_accum));
    }

    uint16_t raw_pressure_avg = sum_pressure / num_samples;
    uint16_t raw_temperature_avg = sum_temperature / num_samples;

    // per datasheet
    float pressure = (raw_pressure_avg - 16384) * (_p_max - _p_min) / 32768 + _p_min + _p_mode_offset;
    pressure *= 100000; // bar -> Pascal
    float temperature = ((raw_temperature_avg >> 4) - 24) * 0.05f - 50;

    _copy_to_frontend(_instance, pressure, temperature);
}

#endif  // AP_BARO_KELLERLD_ENABLED