pi_spi.c

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#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdint.h>
#include <errno.h>
#include <string.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/spi/spidev.h>

#include "pihwm.h"
#include "pi_spi.h"

int
spi_init (uint8_t channel)
{
    int fd;

    if ( check_kernel_module("spidev") < 0 )
    {
        debug ("[%s] Kernel module \"spidev\" not loaded.\n", __func__);
        return -1;
    }

    if ( check_kernel_module("spi_bcm2708") < 0 )
    {
        debug ("[%s] Kernel module \"spi_bcm2708\" not loaded.\n", __func__);
        return -1;
    }

    if ( channel == 0 )
    {
        fd = open("/dev/spidev0.0", O_RDWR);
    }
    else if ( channel == 1 )
    {
        fd = open("/dev/spidev0.1", O_RDWR);
    }
    else
    {
        debug ("[%s] Invalid SPI channel: %d\n", __func__, channel);
        fd = -1;
    }

    if ( fd < 0 )
    {
        debug ("[%s] Can't open SPI device.\n", __func__);
        return -1;
    }
    else
    {
        // device open, config default values
        if ( spi_config_default(fd) )
        {
            return fd;
        }
        else
        {
            debug ("[%s] Can't set default SPI config.\n", __func__);
            return -1;
        }
    }
}


int
spi_config(int fd, uint8_t mode, uint8_t bits, uint32_t speed, uint16_t delay)
{
    int ret;

    //spi mode
    ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
    if ( ret == -1 )
    {
        debug ("[%s] Can't set SPI mode.\n", __func__);
        return -1;
    }

    // bits per word
    ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
    if ( ret == -1 )
    {
        debug ("[%s] Can't set SPI bits per word.\n", __func__);
        return -1;
    }

    // max speed hz
    ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
    if ( ret == -1 )
    {
        debug ("[%s] Can't set SPI max speed.\n", __func__);
        return -1;
    }

    return 1;
}

int
spi_config_default(int fd)
{
    int ret;

    ret = spi_config (fd, SPI_DEFAULT_MODE, SPI_DEFAULT_BPW, SPI_DEFAULT_SPEED, SPI_DEFAULT_DELAY);

    return ret;
}

int
spi_transfer (int fd, uint8_t txbuf[], uint8_t rxbuf[], uint8_t len)
{
    int ret;

    struct spi_ioc_transfer transfer = {
        .tx_buf = (unsigned long)txbuf,
        .rx_buf = (unsigned long)rxbuf,
        .len = len,
        .delay_usecs = SPI_DEFAULT_DELAY,
        .speed_hz = SPI_DEFAULT_SPEED,
        .bits_per_word = SPI_DEFAULT_BPW,
    };

    ret = ioctl(fd, SPI_IOC_MESSAGE(1), &transfer);
    if ( ret < 1 )
    {
        debug ("[%s] Can't send SPI message.\n", __func__);
        return -1;
    }
    else
    {
        return 1;
    }
}