SPI.hpp

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/**
 * @file SPI.hpp
 *
 * Base class for devices connected via SPI.
 */

#pragma once

#include "../CDev.hpp"

#include "dev_fs_lib_spi.h"

enum spi_mode_e {
    SPIDEV_MODE0 = 0, /* CPOL=0 CHPHA=0 */
    SPIDEV_MODE1 = 1, /* CPOL=0 CHPHA=1 */
    SPIDEV_MODE2 = 2, /* CPOL=1 CHPHA=0 */
    SPIDEV_MODE3 = 3  /* CPOL=1 CHPHA=1 */
};

namespace device __EXPORT
{

/**
 * Abstract class for character device on SPI
 */
class __EXPORT SPI : public CDev
{
protected:
    /**
     * Constructor
     *
     * @param name      Driver name
     * @param devname   Device node name
     * @param bus       SPI bus on which the device lives
     * @param device    Device handle (used by SPI_SELECT)
     * @param mode      SPI clock/data mode
     * @param frequency SPI clock frequency
     */
    SPI(const char *name, const char *devname, int bus, uint32_t device, enum spi_mode_e mode, uint32_t frequency);
    virtual ~SPI();

    /**
     * Locking modes supported by the driver.
     */
    enum LockMode {
        LOCK_PREEMPTION,    /**< the default; lock against all forms of preemption. */
        LOCK_THREADS,       /**< lock only against other threads, using SPI_LOCK */
        LOCK_NONE       /**< perform no locking, only safe if the bus is entirely private */
    };

    virtual int init();

    /**
     * Check for the presence of the device on the bus.
     */
    virtual int probe() { return PX4_OK; }

    /**
     * Perform a SPI transfer.
     *
     * If called from interrupt context, this interface does not lock
     * the bus and may interfere with non-interrupt-context callers.
     *
     * Clients in a mixed interrupt/non-interrupt configuration must
     * ensure appropriate interlocking.
     *
     * At least one of send or recv must be non-null.
     *
     * @param send      Bytes to send to the device, or nullptr if
     *          no data is to be sent.
     * @param recv      Buffer for receiving bytes from the device,
     *          or nullptr if no bytes are to be received.
     * @param len       Number of bytes to transfer.
     * @return      OK if the exchange was successful, -errno
     *          otherwise.
     */
    int     transfer(uint8_t *send, uint8_t *recv, unsigned len);

    /**
     * Perform a SPI 16 bit transfer.
     *
     * If called from interrupt context, this interface does not lock
     * the bus and may interfere with non-interrupt-context callers.
     *
     * Clients in a mixed interrupt/non-interrupt configuration must
     * ensure appropriate interlocking.
     *
     * At least one of send or recv must be non-null.
     *
     * @param send      Words to send to the device, or nullptr if
     *          no data is to be sent.
     * @param recv      Words for receiving bytes from the device,
     *          or nullptr if no bytes are to be received.
     * @param len       Number of words to transfer.
     * @return      OK if the exchange was successful, -errno
     *          otherwise.
     */
    int     transferhword(uint16_t *send, uint16_t *recv, unsigned len);

    /**
     * Set the SPI bus frequency
     * This is used to change frequency on the fly. Some sensors
     * (such as the MPU6000) need a lower frequency for setup
     * registers and can handle higher frequency for sensor
     * value registers
     *
     * @param frequency Frequency to set (Hz)
     */
    void        set_frequency(uint32_t frequency) { _frequency = frequency; }
    uint32_t        get_frequency() { return _frequency; }

    /**
     * Set the SPI bus locking mode
     *
     * This set the SPI locking mode. For devices competing with NuttX SPI
     * drivers on a bus the right lock mode is LOCK_THREADS.
     *
     * @param mode  Locking mode
     */
    void        set_lockmode(enum LockMode mode) {}

private:
    int             _fd{-1};

    uint32_t        _device;
    enum spi_mode_e     _mode;
    uint32_t        _frequency;

    /* this class does not allow copying */
    SPI(const SPI &);
    SPI operator=(const SPI &);

protected:

    bool    external() { return px4_spi_bus_external(get_device_bus()); }

};

} // namespace device