ardupilot/libraries/AP_Baro/AP_Baro_MS5611.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_MS5611.h"

#include <utility>
#include <stdio.h>

#include <AP_Math/AP_Math.h>

extern const AP_HAL::HAL &hal;

static const uint8_t CMD_MS56XX_RESET = 0x1E;
static const uint8_t CMD_MS56XX_READ_ADC = 0x00;

/* PROM start address */
static const uint8_t CMD_MS56XX_PROM = 0xA0;

/* write to one of these addresses to start pressure conversion */
#define ADDR_CMD_CONVERT_D1_OSR256  0x40
#define ADDR_CMD_CONVERT_D1_OSR512  0x42
#define ADDR_CMD_CONVERT_D1_OSR1024 0x44
#define ADDR_CMD_CONVERT_D1_OSR2048 0x46
#define ADDR_CMD_CONVERT_D1_OSR4096 0x48

/* write to one of these addresses to start temperature conversion */
#define ADDR_CMD_CONVERT_D2_OSR256  0x50
#define ADDR_CMD_CONVERT_D2_OSR512  0x52
#define ADDR_CMD_CONVERT_D2_OSR1024 0x54
#define ADDR_CMD_CONVERT_D2_OSR2048 0x56
#define ADDR_CMD_CONVERT_D2_OSR4096 0x58

/*
  use an OSR of 1024 to reduce the self-heating effect of the
  sensor. Information from MS tells us that some individual sensors
  are quite sensitive to this effect and that reducing the OSR can
  make a big difference
 */
static const uint8_t ADDR_CMD_CONVERT_PRESSURE = ADDR_CMD_CONVERT_D1_OSR1024;
static const uint8_t ADDR_CMD_CONVERT_TEMPERATURE = ADDR_CMD_CONVERT_D2_OSR1024;

/*
  constructor
 */
AP_Baro_MS56XX::AP_Baro_MS56XX(AP_Baro &baro, AP_HAL::OwnPtr<AP_HAL::Device> dev)
    : AP_Baro_Backend(baro)
    , _dev(std::move(dev))
{
}

void AP_Baro_MS56XX::_init()
{
    if (!_dev) {
        printf("MS5611: no device available");
        return;
    }

    if (!_dev->get_semaphore()->take(10)) {
        AP_HAL::panic("PANIC: AP_Baro_MS56XX: failed to take serial semaphore for init");
    }

    uint16_t prom[8];
    if (!_read_prom(prom)) {
        printf("MS5611: Can't read PROM on bus %d", _dev->get_bus_id());
        _dev->get_semaphore()->give();
        return;
    }

    _dev->transfer(&CMD_MS56XX_RESET, 1, nullptr, 0);
    hal.scheduler->delay(4);

    // Save factory calibration coefficients
    _cal_reg.c1 = prom[1];
    _cal_reg.c2 = prom[2];
    _cal_reg.c3 = prom[3];
    _cal_reg.c4 = prom[4];
    _cal_reg.c5 = prom[5];
    _cal_reg.c6 = prom[6];

    // Send a command to read temperature first
    _dev->transfer(&ADDR_CMD_CONVERT_TEMPERATURE, 1, nullptr, 0);
    _state = 0;

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

    _instance = _frontend.register_sensor();

    _dev->get_semaphore()->give();

    /* Request 100Hz update */
    _dev->register_periodic_callback(10 * USEC_PER_MSEC,
                                     FUNCTOR_BIND_MEMBER(&AP_Baro_MS56XX::_timer, bool));
}

/**
 * MS56XX crc4 method from datasheet for 16 bytes (8 short values)
 */
static uint16_t crc4(uint16_t *data)
{
    uint16_t n_rem = 0;
    uint8_t n_bit;

    for (uint8_t cnt = 0; cnt < 16; cnt++) {
        /* uneven bytes */
        if (cnt & 1) {
            n_rem ^= (uint8_t)((data[cnt >> 1]) & 0x00FF);
        } else {
            n_rem ^= (uint8_t)(data[cnt >> 1] >> 8);
        }

        for (n_bit = 8; n_bit > 0; n_bit--) {
            if (n_rem & 0x8000) {
                n_rem = (n_rem << 1) ^ 0x3000;
            } else {
                n_rem = (n_rem << 1);
            }
        }
    }

    return (n_rem >> 12) & 0xF;
}

uint16_t AP_Baro_MS56XX::_read_prom_word(uint8_t word)
{
    const uint8_t reg = CMD_MS56XX_PROM + (word << 1);
    uint8_t val[2];

    if (!_dev->transfer(&reg, 1, val, 2)) {
        return 0;
    }
    return (val[0] << 8) | val[1];
}

uint32_t AP_Baro_MS56XX::_read_adc()
{
    uint8_t val[3];

    if (!_dev->transfer(&CMD_MS56XX_READ_ADC, 1, val, 3)) {
        return 0;
    }
    return (val[0] << 16) | (val[1] << 8) | val[2];
}

bool AP_Baro_MS56XX::_read_prom(uint16_t prom[8])
{
    /*
     * MS5611-01BA datasheet, CYCLIC REDUNDANCY CHECK (CRC): "MS5611-01BA
     * contains a PROM memory with 128-Bit. A 4-bit CRC has been implemented
     * to check the data validity in memory."
     *
     * CRC field must me removed for CRC-4 calculation.
     */
    for (uint8_t i = 0; i < 8; i++) {
        prom[i] = _read_prom_word(i);
    }

    /* save the read crc */
    const uint16_t crc_read = prom[7] & 0xf;

    /* remove CRC byte */
    prom[7] &= 0xff00;

    return crc_read == crc4(prom);
}

bool AP_Baro_MS5637::_read_prom(uint16_t prom[8])
{
    /*
     * MS5637-02BA03 datasheet, CYCLIC REDUNDANCY CHECK (CRC): "MS5637
     * contains a PROM memory with 112-Bit. A 4-bit CRC has been implemented
     * to check the data validity in memory."
     *
     * 8th PROM word must be zeroed and CRC field removed for CRC-4
     * calculation.
     */
    for (uint8_t i = 0; i < 7; i++) {
        prom[i] = _read_prom_word(i);
    }

    prom[7] = 0;

    /* save the read crc */
    const uint16_t crc_read = (prom[0] & 0xf000) >> 12;

    /* remove CRC byte */
    prom[0] &= ~0xf000;

    return crc_read == crc4(prom);
}

/*
 * Read the sensor with a state machine
 * We read one time temperature (state=0) and then 4 times pressure (states 1-4)
 *
 * Temperature is used to calculate the compensated pressure and doesn't vary
 * as fast as pressure. Hence we reuse the same temperature for 4 samples of
 * pressure.
*/
bool AP_Baro_MS56XX::_timer(void)
{
    uint8_t next_cmd;
    uint8_t next_state;
    uint32_t adc_val = _read_adc();

    /*
     * If read fails, re-initiate a read command for current state or we are
     * stuck
     */
    if (adc_val == 0) {
        next_state = _state;
    } else {
        next_state = (_state + 1) % 5;
    }

    next_cmd = next_state == 0 ? ADDR_CMD_CONVERT_TEMPERATURE
                               : ADDR_CMD_CONVERT_PRESSURE;
    _dev->transfer(&next_cmd, 1, nullptr, 0);

    /* if we had a failed read we are all done */
    if (adc_val == 0) {
        return true;
    }

    if (_sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        if (_state == 0) {
            _update_and_wrap_accumulator(&_accum.s_D2, adc_val,
                                         &_accum.d2_count, 32);
        } else {
            _update_and_wrap_accumulator(&_accum.s_D1, adc_val,
                                         &_accum.d1_count, 128);
        }
        _sem->give();
        _state = next_state;
    }

    return true;
}

void AP_Baro_MS56XX::_update_and_wrap_accumulator(uint32_t *accum, uint32_t val,
                                                  uint8_t *count, uint8_t max_count)
{
    *accum += val;
    *count += 1;
    if (*count == max_count) {
        *count = max_count / 2;
        *accum = *accum / 2;
    }
}

void AP_Baro_MS56XX::update()
{
    uint32_t sD1, sD2;
    uint8_t d1count, d2count;

    if (!_sem->take_nonblocking()) {
        return;
    }

    if (_accum.d1_count == 0) {
        _sem->give();
        return;
    }

    sD1 = _accum.s_D1;
    sD2 = _accum.s_D2;
    d1count = _accum.d1_count;
    d2count = _accum.d2_count;
    memset(&_accum, 0, sizeof(_accum));

    _sem->give();

    if (d1count != 0) {
        _D1 = ((float)sD1) / d1count;
    }
    if (d2count != 0) {
        _D2 = ((float)sD2) / d2count;
    }
    _calculate();
}

/* MS5611 class */
AP_Baro_MS5611::AP_Baro_MS5611(AP_Baro &baro, AP_HAL::OwnPtr<AP_HAL::Device> dev)
    : AP_Baro_MS56XX(baro, std::move(dev))
{
    _init();
}

// Calculate Temperature and compensated Pressure in real units (Celsius degrees*100, mbar*100).
void AP_Baro_MS5611::_calculate()
{
    float dT;
    float TEMP;
    float OFF;
    float SENS;

    // Formulas from manufacturer datasheet
    // sub -15c temperature compensation is not included

    // we do the calculations using floating point allows us to take advantage
    // of the averaging of D1 and D1 over multiple samples, giving us more
    // precision
    dT = _D2-(((uint32_t)_cal_reg.c5)<<8);
    TEMP = (dT * _cal_reg.c6)/8388608;
    OFF = _cal_reg.c2 * 65536.0f + (_cal_reg.c4 * dT) / 128;
    SENS = _cal_reg.c1 * 32768.0f + (_cal_reg.c3 * dT) / 256;

    if (TEMP < 0) {
        // second order temperature compensation when under 20 degrees C
        float T2 = (dT*dT) / 0x80000000;
        float Aux = TEMP*TEMP;
        float OFF2 = 2.5f*Aux;
        float SENS2 = 1.25f*Aux;
        TEMP = TEMP - T2;
        OFF = OFF - OFF2;
        SENS = SENS - SENS2;
    }

    float pressure = (_D1*SENS/2097152 - OFF)/32768;
    float temperature = (TEMP + 2000) * 0.01f;
    _copy_to_frontend(_instance, pressure, temperature);
}

/* MS5607 Class */
AP_Baro_MS5607::AP_Baro_MS5607(AP_Baro &baro, AP_HAL::OwnPtr<AP_HAL::Device> dev)
    : AP_Baro_MS56XX(baro, std::move(dev))
{
    _init();
}

// Calculate Temperature and compensated Pressure in real units (Celsius degrees*100, mbar*100).
void AP_Baro_MS5607::_calculate()
{
    float dT;
    float TEMP;
    float OFF;
    float SENS;

    // Formulas from manufacturer datasheet
    // sub -15c temperature compensation is not included

    // we do the calculations using floating point allows us to take advantage
    // of the averaging of D1 and D1 over multiple samples, giving us more
    // precision
    dT = _D2-(((uint32_t)_cal_reg.c5)<<8);
    TEMP = (dT * _cal_reg.c6)/8388608;
    OFF = _cal_reg.c2 * 131072.0f + (_cal_reg.c4 * dT) / 64;
    SENS = _cal_reg.c1 * 65536.0f + (_cal_reg.c3 * dT) / 128;

    if (TEMP < 0) {
        // second order temperature compensation when under 20 degrees C
        float T2 = (dT*dT) / 0x80000000;
        float Aux = TEMP*TEMP;
        float OFF2 = 61.0f*Aux/16.0f;
        float SENS2 = 2.0f*Aux;
        TEMP = TEMP - T2;
        OFF = OFF - OFF2;
        SENS = SENS - SENS2;
    }

    float pressure = (_D1*SENS/2097152 - OFF)/32768;
    float temperature = (TEMP + 2000) * 0.01f;
    _copy_to_frontend(_instance, pressure, temperature);
}

/* MS5637 Class */
AP_Baro_MS5637::AP_Baro_MS5637(AP_Baro &baro, AP_HAL::OwnPtr<AP_HAL::Device> dev)
    : AP_Baro_MS56XX(baro, std::move(dev))
{
    _init();
}

// Calculate Temperature and compensated Pressure in real units (Celsius degrees*100, mbar*100).
void AP_Baro_MS5637::_calculate()
{
    int32_t dT, TEMP;
    int64_t OFF, SENS;
    int32_t raw_pressure = _D1;
    int32_t raw_temperature = _D2;

    // Formulas from manufacturer datasheet
    // sub -15c temperature compensation is not included

    dT = raw_temperature - (((uint32_t)_cal_reg.c5) << 8);
    TEMP = 2000 + ((int64_t)dT * (int64_t)_cal_reg.c6) / 8388608;
    OFF = (int64_t)_cal_reg.c2 * (int64_t)131072 + ((int64_t)_cal_reg.c4 * (int64_t)dT) / (int64_t)64;
    SENS = (int64_t)_cal_reg.c1 * (int64_t)65536 + ((int64_t)_cal_reg.c3 * (int64_t)dT) / (int64_t)128;

    if (TEMP < 2000) {
        // second order temperature compensation when under 20 degrees C
        int32_t T2 = ((int64_t)3 * ((int64_t)dT * (int64_t)dT) / (int64_t)8589934592);
        int64_t aux = (TEMP - 2000) * (TEMP - 2000);
        int64_t OFF2 = 61 * aux / 16;
        int64_t SENS2 = 29 * aux / 16;

        TEMP = TEMP - T2;
        OFF = OFF - OFF2;
        SENS = SENS - SENS2;
    }

    int32_t pressure = ((int64_t)raw_pressure * SENS / (int64_t)2097152 - OFF) / (int64_t)32768;
    float temperature = TEMP * 0.01f;
    _copy_to_frontend(_instance, (float)pressure, temperature);
}