/*

 * dac7562 (using spidev driver)

 *

  */

#include <stdint.h>

#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

#include <getopt.h>

#include <fcntl.h>

#include <sys/ioctl.h>

#include <linux/types.h>

#include <linux/spi/spidev.h>

#define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))

static const char *device = "/dev/spidev0.0";

static uint8_t mode;

static uint8_t bits = 24;

static uint32_t speed = 500000;

static uint16_t delay;

static void transfer(int fd, int cmd)

{

    int ret;

    uint8_t tx[3] ;

    tx[0] = (uint8_t)(cmd >> 24)    // 24bit 命令格式参见表格　１２　１３　以及　１７

    tx[1] = (uint8_t)(cmd >> 16);  //

    tx[2] = (uint8_t)(cmd >> 0);   //

  

    struct spi_ioc_transfer tr = {

        .tx_buf = (unsigned long)tx,

        .rx_buf = NULL,

        .len = 3,

        .delay_usecs = delay,

        .speed_hz = speed,

        .bits_per_word = bits,

    };

    ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);

    if (ret < 1)

        printf("can't send spi message");

    puts("");

}

int main(int argc, char *argv[])

{

    int ret = 0;

    int fd;

  

    fd = open(device, O_RDWR);

    if (fd < 0)

        printf("can't open device");

     mode |= SPI_CPOL;

    /*

     * spi mode

     */

    ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);

    if (ret == -1)

        printf("can't set spi mode");

   

    /*

     * bits per word

     */

    ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);

    if (ret == -1)

        printf("can't set bits per word");

 

    /*

     * max speed hz

     */

    ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);

    if (ret == -1)

        printf("can't set max speed hz");

  

    printf("spi mode: %d\n", mode);

    printf("bits per word: %d\n", bits);

    printf("max speed: %d Hz (%d KHz)\n", speed, speed/1000);

    transfer(fd);

    close(fd);

    return ret;

}