MPU9250_mag.cpp

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/**
 * @file mag.cpp
 *
 * Driver for the ak8963 magnetometer within the Invensense mpu9250
 *
 * @author Robert Dickenson
 *
 */

#include <px4_platform_common/px4_config.h>
#include <px4_platform_common/log.h>
#include <px4_platform_common/time.h>
#include <lib/perf/perf_counter.h>
#include <drivers/drv_hrt.h>

#include "MPU9250_mag.h"
#include "mpu9250.h"

// If interface is non-null, then it will used for interacting with the device.
// Otherwise, it will passthrough the parent MPU9250
MPU9250_mag::MPU9250_mag(MPU9250 *parent, device::Device *interface, enum Rotation rotation) :
    _interface(interface),
    _px4_mag(parent->_interface->get_device_id(), (parent->_interface->external() ? ORB_PRIO_MAX : ORB_PRIO_HIGH),
         rotation),
    _parent(parent),
    _mag_overruns(perf_alloc(PC_COUNT, MODULE_NAME": mag_overruns")),
    _mag_overflows(perf_alloc(PC_COUNT, MODULE_NAME": mag_overflows")),
    _mag_errors(perf_alloc(PC_COUNT, MODULE_NAME": mag_errors"))
{
    _px4_mag.set_device_type(DRV_MAG_DEVTYPE_MPU9250);
    _px4_mag.set_scale(MPU9250_MAG_RANGE_GA);
}

MPU9250_mag::~MPU9250_mag()
{
    perf_free(_mag_overruns);
    perf_free(_mag_overflows);
    perf_free(_mag_errors);
}

void
MPU9250_mag::measure()
{
    const hrt_abstime timestamp_sample = hrt_absolute_time();

    uint8_t st1 = 0;
    int ret = _interface->read(AK8963REG_ST1, &st1, sizeof(st1));

    if (ret != OK) {
        _px4_mag.set_error_count(perf_event_count(_mag_errors));
        return;
    }

    /* Check if data ready is set.
     * This is not described to be set in continuous mode according to the
     * MPU9250 datasheet. However, the datasheet of the 8963 recommends to
     * check data ready before doing the read and before triggering the
     * next measurement by reading ST2. */
    if (!(st1 & AK09916_ST1_DRDY)) {
        return;
    }

    /* Monitor if data overrun flag is ever set. */
    if (st1 & 0x02) {
        perf_count(_mag_overruns);
    }

    ak8963_regs data{};
    ret = _interface->read(AK8963REG_ST1, &data, sizeof(data));

    if (ret != OK) {
        _px4_mag.set_error_count(perf_event_count(_mag_errors));
        return;
    }

    /* Monitor magnetic sensor overflow flag. */
    if (data.st2 & 0x08) {
        perf_count(_mag_overflows);
    }

    _measure(timestamp_sample, data);
}

void
MPU9250_mag::_measure(hrt_abstime timestamp_sample, ak8963_regs data)
{
    /* Check if data ready is set.
     * This is not described to be set in continuous mode according to the
     * MPU9250 datasheet. However, the datasheet of the 8963 recommends to
     * check data ready before doing the read and before triggering the
     * next measurement by reading ST2.
     *
     * If _measure is used in passthrough mode, all the data is already
     * fetched, however, we should still not use the data if the data ready
     * is not set. This has lead to intermittent spikes when the data was
     * being updated while getting read.
     */
    if (!(data.st1 & AK09916_ST1_DRDY)) {
        return;
    }

    _px4_mag.set_external(_parent->is_external());
    _px4_mag.set_temperature(_parent->_last_temperature);

    /*
     * Align axes - note the accel & gyro are also re-aligned so this
     *              doesn't look obvious with the datasheet
     */
    _px4_mag.update(timestamp_sample, data.x, -data.y, -data.z);
}

void
MPU9250_mag::set_passthrough(uint8_t reg, uint8_t size, uint8_t *out)
{
    uint8_t addr;

    _parent->write_reg(MPUREG_I2C_SLV0_CTRL, 0); // ensure slave r/w is disabled before changing the registers

    if (out) {
        _parent->write_reg(MPUREG_I2C_SLV0_D0, *out);
        addr = AK8963_I2C_ADDR;

    } else {
        addr = AK8963_I2C_ADDR | BIT_I2C_READ_FLAG;
    }

    _parent->write_reg(MPUREG_I2C_SLV0_ADDR, addr);
    _parent->write_reg(MPUREG_I2C_SLV0_REG,  reg);
    _parent->write_reg(MPUREG_I2C_SLV0_CTRL, size | BIT_I2C_SLV0_EN);
}

void
MPU9250_mag::read_block(uint8_t reg, uint8_t *val, uint8_t count)
{
    _parent->_interface->read(reg, val, count);
}

void
MPU9250_mag::passthrough_read(uint8_t reg, uint8_t *buf, uint8_t size)
{
    set_passthrough(reg, size);
    px4_usleep(25 + 25 * size); // wait for the value to be read from slave
    read_block(MPUREG_EXT_SENS_DATA_00, buf, size);
    _parent->write_reg(MPUREG_I2C_SLV0_CTRL, 0); // disable new reads
}

uint8_t
MPU9250_mag::read_reg(unsigned int reg)
{
    uint8_t buf{};

    if (_interface == nullptr) {
        passthrough_read(reg, &buf, 0x01);

    } else {
        _interface->read(reg, &buf, 1);
    }

    return buf;
}

bool
MPU9250_mag::ak8963_check_id(uint8_t &deviceid)
{
    deviceid = read_reg(AK8963REG_WIA);

    return (AK8963_DEVICE_ID == deviceid);
}

/*
 * 400kHz I2C bus speed = 2.5us per bit = 25us per byte
 */
void
MPU9250_mag::passthrough_write(uint8_t reg, uint8_t val)
{
    set_passthrough(reg, 1, &val);
    px4_usleep(50); // wait for the value to be written to slave
    _parent->write_reg(MPUREG_I2C_SLV0_CTRL, 0); // disable new writes
}

void
MPU9250_mag::write_reg(unsigned reg, uint8_t value)
{
    // general register transfer at low clock speed
    if (_interface == nullptr) {
        passthrough_write(reg, value);

    } else {
        _interface->write(MPU9250_LOW_SPEED_OP(reg), &value, 1);
    }
}

int
MPU9250_mag::ak8963_reset()
{
    // First initialize it to use the bus
    int rv = ak8963_setup();

    if (rv == OK) {
        // Now reset the mag
        write_reg(AK8963REG_CNTL2, AK8963_RESET);

        // Then re-initialize the bus/mag
        rv = ak8963_setup();
    }

    return rv;
}

bool
MPU9250_mag::ak8963_read_adjustments()
{
    uint8_t response[3];
    float ak8963_ASA[3];

    write_reg(AK8963REG_CNTL1, AK8963_FUZE_MODE | AK8963_16BIT_ADC);
    px4_usleep(50);

    if (_interface != nullptr) {
        _interface->read(AK8963REG_ASAX, response, 3);

    } else {
        passthrough_read(AK8963REG_ASAX, response, 3);
    }

    write_reg(AK8963REG_CNTL1, AK8963_POWERDOWN_MODE);

    for (int i = 0; i < 3; i++) {
        if (0 != response[i] && 0xff != response[i]) {
            ak8963_ASA[i] = ((float)(response[i] - 128) / 256.0f) + 1.0f;

        } else {
            return false;
        }
    }

    _px4_mag.set_sensitivity(ak8963_ASA[0], ak8963_ASA[1], ak8963_ASA[2]);

    return true;
}

int
MPU9250_mag::ak8963_setup_master_i2c()
{
    /* When _interface is null we are using SPI and must
     * use the parent interface to configure the device to act
     * in master mode (SPI to I2C bridge)
     */
    if (_interface == nullptr) {
        if (_parent->_whoami == MPU_WHOAMI_9250) {
            _parent->modify_checked_reg(MPUREG_USER_CTRL, 0, BIT_I2C_MST_EN);
            _parent->write_reg(MPUREG_I2C_MST_CTRL, BIT_I2C_MST_P_NSR | BIT_I2C_MST_WAIT_FOR_ES | BITS_I2C_MST_CLOCK_400HZ);
        }

    } else {
        _parent->modify_checked_reg(MPUREG_USER_CTRL, BIT_I2C_MST_EN, 0);
    }

    return OK;
}
int
MPU9250_mag::ak8963_setup()
{
    int retries = 10;

    do {
        ak8963_setup_master_i2c();
        write_reg(AK8963REG_CNTL2, AK8963_RESET);

        uint8_t id = 0;

        if (ak8963_check_id(id)) {
            break;
        }

        retries--;
        PX4_WARN("AK8963: bad id %d retries %d", id, retries);
        _parent->modify_reg(MPUREG_USER_CTRL, 0, BIT_I2C_MST_RST);
        px4_usleep(100);
    } while (retries > 0);

    if (retries > 0) {
        retries = 10;

        while (!ak8963_read_adjustments() && retries) {
            retries--;
            PX4_ERR("AK8963: failed to read adjustment data. Retries %d", retries);

            _parent->modify_reg(MPUREG_USER_CTRL, 0, BIT_I2C_MST_RST);
            px4_usleep(100);
            ak8963_setup_master_i2c();
            write_reg(AK8963REG_CNTL2, AK8963_RESET);
        }
    }

    if (retries == 0) {
        PX4_ERR("AK8963: failed to initialize, disabled!");
        _parent->modify_checked_reg(MPUREG_USER_CTRL, BIT_I2C_MST_EN, 0);
        _parent->write_reg(MPUREG_I2C_MST_CTRL, 0);

        return -EIO;
    }

    if (_parent->_whoami == MPU_WHOAMI_9250) {
        write_reg(AK8963REG_CNTL1, AK8963_CONTINUOUS_MODE2 | AK8963_16BIT_ADC);
    }

    if (_interface == nullptr) {
        // Configure mpu' I2C Master interface to read ak8963 data into to fifo
        if (_parent->_whoami == MPU_WHOAMI_9250) {
            set_passthrough(AK8963REG_ST1, sizeof(ak8963_regs));
        }
    }

    return OK;
}