ms5611_spi.cpp

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/**
 * @file ms5611_spi.cpp
 *
 * SPI interface for MS5611
 */

#include "ms5611.h"

/* SPI protocol address bits */
#define DIR_READ            (1<<7)
#define DIR_WRITE           (0<<7)
#define ADDR_INCREMENT          (1<<6)

#if defined(PX4_SPIDEV_BARO) || defined(PX4_SPIDEV_EXT_BARO)

device::Device *MS5611_spi_interface(ms5611::prom_u &prom_buf, bool external_bus);

class MS5611_SPI : public device::SPI
{
public:
    MS5611_SPI(uint8_t bus, uint32_t device, ms5611::prom_u &prom_buf);
    virtual ~MS5611_SPI() = default;

    virtual int init();
    virtual int read(unsigned offset, void *data, unsigned count);
    virtual int ioctl(unsigned operation, unsigned &arg);

private:
    ms5611::prom_u  &_prom;

    /**
     * Send a reset command to the MS5611.
     *
     * This is required after any bus reset.
     */
    int     _reset();

    /**
     * Send a measure command to the MS5611.
     *
     * @param addr      Which address to use for the measure operation.
     */
    int     _measure(unsigned addr);

    /**
     * Read the MS5611 PROM
     *
     * @return      OK if the PROM reads successfully.
     */
    int     _read_prom();

    /**
     * Read a 16-bit register value.
     *
     * @param reg       The register to read.
     */
    uint16_t    _reg16(unsigned reg);

    /**
     * Wrapper around transfer() that prevents interrupt-context transfers
     * from pre-empting us. The sensor may (does) share a bus with sensors
     * that are polled from interrupt context (or we may be pre-empted)
     * so we need to guarantee that transfers complete without interruption.
     */
    int     _transfer(uint8_t *send, uint8_t *recv, unsigned len);
};

device::Device *
MS5611_spi_interface(ms5611::prom_u &prom_buf, uint8_t busnum)
{
#ifdef PX4_SPI_BUS_EXT

    if (busnum == PX4_SPI_BUS_EXT) {
#ifdef PX4_SPIDEV_EXT_BARO
        return new MS5611_SPI(busnum, PX4_SPIDEV_EXT_BARO, prom_buf);
#else
        return nullptr;
#endif
    }

#endif
    return new MS5611_SPI(busnum, PX4_SPIDEV_BARO, prom_buf);
}

MS5611_SPI::MS5611_SPI(uint8_t bus, uint32_t device, ms5611::prom_u &prom_buf) :
    SPI("MS5611_SPI", nullptr, bus, device, SPIDEV_MODE3, 20 * 1000 * 1000 /* will be rounded to 10.4 MHz */),
    _prom(prom_buf)
{
}

int
MS5611_SPI::init()
{
    int ret = SPI::init();

    if (ret != OK) {
        PX4_DEBUG("SPI init failed");
        goto out;
    }

    /* send reset command */
    ret = _reset();

    if (ret != OK) {
        PX4_DEBUG("reset failed");
        goto out;
    }

    /* read PROM */
    ret = _read_prom();

    if (ret != OK) {
        PX4_DEBUG("prom readout failed");
        goto out;
    }

out:
    return ret;
}

int
MS5611_SPI::read(unsigned offset, void *data, unsigned count)
{
    union _cvt {
        uint8_t b[4];
        uint32_t w;
    } *cvt = (_cvt *)data;
    uint8_t buf[4] = { 0 | DIR_WRITE, 0, 0, 0 };

    /* read the most recent measurement */
    int ret = _transfer(&buf[0], &buf[0], sizeof(buf));

    if (ret == OK) {
        /* fetch the raw value */
        cvt->b[0] = buf[3];
        cvt->b[1] = buf[2];
        cvt->b[2] = buf[1];
        cvt->b[3] = 0;

        ret = count;
    }

    return ret;
}

int
MS5611_SPI::ioctl(unsigned operation, unsigned &arg)
{
    int ret;

    switch (operation) {
    case IOCTL_RESET:
        ret = _reset();
        break;

    case IOCTL_MEASURE:
        ret = _measure(arg);
        break;

    default:
        ret = EINVAL;
    }

    if (ret != OK) {
        errno = ret;
        return -1;
    }

    return 0;
}

int
MS5611_SPI::_reset()
{
    uint8_t cmd = ADDR_RESET_CMD | DIR_WRITE;

    return  _transfer(&cmd, nullptr, 1);
}

int
MS5611_SPI::_measure(unsigned addr)
{
    uint8_t cmd = addr | DIR_WRITE;

    return _transfer(&cmd, nullptr, 1);
}


int
MS5611_SPI::_read_prom()
{
    /*
     * Wait for PROM contents to be in the device (2.8 ms) in the case we are
     * called immediately after reset.
     */
    px4_usleep(3000);

    /* read and convert PROM words */
    bool all_zero = true;

    for (int i = 0; i < 8; i++) {
        uint8_t cmd = (ADDR_PROM_SETUP + (i * 2));
        _prom.c[i] = _reg16(cmd);

        if (_prom.c[i] != 0) {
            all_zero = false;
        }

        //PX4_DEBUG("prom[%u]=0x%x", (unsigned)i, (unsigned)_prom.c[i]);
    }

    /* calculate CRC and return success/failure accordingly */
    int ret = ms5611::crc4(&_prom.c[0]) ? OK : -EIO;

    if (ret != OK) {
        PX4_DEBUG("crc failed");
    }

    if (all_zero) {
        PX4_DEBUG("prom all zero");
        ret = -EIO;
    }

    return ret;
}

uint16_t
MS5611_SPI::_reg16(unsigned reg)
{
    uint8_t cmd[3] = { (uint8_t)(reg | DIR_READ), 0, 0 };

    _transfer(cmd, cmd, sizeof(cmd));

    return (uint16_t)(cmd[1] << 8) | cmd[2];
}

int
MS5611_SPI::_transfer(uint8_t *send, uint8_t *recv, unsigned len)
{
    return transfer(send, recv, len);
}

#endif /* PX4_SPIDEV_BARO || PX4_SPIDEV_EXT_BARO */