ms5611_spi.cpp

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

#include <drivers/device/spi.h>
#include "ms5611.h"

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


class MS5611_SPI : public device::SPI
{
public:
	MS5611_SPI(uint8_t bus, uint32_t device, ms5611::prom_u &prom_buf, int bus_frequency, spi_mode_e spi_mode);
	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, uint32_t devid, uint8_t busnum, int bus_frequency, spi_mode_e spi_mode)
{
	return new MS5611_SPI(busnum, devid, prom_buf, bus_frequency, spi_mode);
}

MS5611_SPI::MS5611_SPI(uint8_t bus, uint32_t device, ms5611::prom_u &prom_buf, int bus_frequency, spi_mode_e spi_mode) :
	SPI(DRV_BARO_DEVTYPE_MS5611, MODULE_NAME, bus, device, spi_mode, bus_frequency),
	_prom(prom_buf)
{
}

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

	if (ret != OK) {
		PX4_DEBUG("SPI init failed");
		return PX4_ERROR;
	}

	// reset and read PROM (try up to 3 times)
	for (int i = 0; i < 3; i++) {
		/* send reset command */
		ret = _reset();

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

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

		if (ret == OK) {
			return PX4_OK;

		} else {
			PX4_DEBUG("prom readout failed");
			continue;
		}
	}

	return PX4_ERROR;
}

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);
}