linux spi 设备节点读写

布满荆棘的人生 2023-08-17 15:58 45阅读 0赞

本文记录spi设备节点的操作方法。

SPI总线设备文件名通常为/dev/spidevN.P（N=0、1、2……，P=0、1、2……），

其中N表示第几路SPI总线，而P表示在该路SPI总线中使用哪个CS信号线。

参考链接：

[http://www.wzaobao.com/p/l5079K.html][http_www.wzaobao.com_p_l5079K.html]

[http://www.emcraft.com/stm32f429discovery/accessing-spi-devices-in-linux][http_www.emcraft.com_stm32f429discovery_accessing-spi-devices-in-linux]

[http://blog.csdn.net/yuanlulu/article/details/6320740][http_blog.csdn.net_yuanlulu_article_details_6320740]

程序

kernel/Documentation/spi/spidev\_test.c

编译之后，MISO和MOSI连接，能够收到发送的数据。

#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 void pabort(const char *s)
    
    {
    
    perror(s);
    
    abort();
    
    }
    
    
    static const char *device = "/dev/spidev1.0";
    
    static uint8_t mode;
    
    static uint8_t bits = 8;
    
    static uint32_t speed = 500000;
    
    static uint16_t delay;
    
    
    static void transfer(int fd)
    
    {
    
    int ret;
    
    uint8_t tx[] = {
    
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
    
    0x40, 0x00, 0x00, 0x00, 0x00, 0x95,
    
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
    
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
    
    0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
    
    0xDE, 0xAD, 0xBE, 0xEF, 0xBA, 0xAD,
    
    0xF0, 0x0D,
    
    };
    
    uint8_t rx[ARRAY_SIZE(tx)] = {0, };
    
    struct spi_ioc_transfer tr = {
    
    .tx_buf = (unsigned long)tx, //发送缓存区
    
    .rx_buf = (unsigned long)rx, //接收缓存区
    
    .len = ARRAY_SIZE(tx),
    
    .delay_usecs = delay, //发送时间间隔
    
    .speed_hz = speed, //总线速率
    
    .bits_per_word = bits, //收发的一个字的二进制位数
    
    };
    
    
    ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);
    
    if (ret < 1)
    
    pabort("can't send spi message");
    
    
    for (ret = 0; ret < ARRAY_SIZE(tx); ret++) {
    
    if (!(ret % 6))
    
    puts("");
    
    printf("%.2X ", rx[ret]);
    
    }
    
    puts("");
    
    }
    
    
    static void print_usage(const char *prog)
    
    {
    
    printf("Usage: %s [-DsbdlHOLC3]\n", prog);
    
    puts(" -D --device device to use (default /dev/spidev1.1)\n"
    
    " -s --speed max speed (Hz)\n"
    
    " -d --delay delay (usec)\n"
    
    " -b --bpw bits per word \n"
    
    " -l --loop loopback\n"
    
    " -H --cpha clock phase\n"
    
    " -O --cpol clock polarity\n"
    
    " -L --lsb least significant bit first\n"
    
    " -C --cs-high chip select active high\n"
    
    " -3 --3wire SI/SO signals shared\n");
    
    exit(1);
    
    }
    
    
    static void parse_opts(int argc, char *argv[])
    
    {
    
    while (1) {
    
    static const struct option lopts[] = {
    
    { "device", 1, 0, 'D' },
    
    { "speed", 1, 0, 's' },
    
    { "delay", 1, 0, 'd' },
    
    { "bpw", 1, 0, 'b' },
    
    { "loop", 0, 0, 'l' },
    
    { "cpha", 0, 0, 'H' },
    
    { "cpol", 0, 0, 'O' },
    
    { "lsb", 0, 0, 'L' },
    
    { "cs-high", 0, 0, 'C' },
    
    { "3wire", 0, 0, '3' },
    
    { "no-cs", 0, 0, 'N' },
    
    { "ready", 0, 0, 'R' },
    
    { NULL, 0, 0, 0 },
    
    };
    
    int c;
    
    
    c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, NULL);
    
    
    if (c == -1)
    
    break;
    
    
    switch (c) {
    
    case 'D':
    
    device = optarg;
    
    break;
    
    case 's':
    
    speed = atoi(optarg);
    
    break;
    
    case 'd':
    
    delay = atoi(optarg);
    
    break;
    
    case 'b':
    
    bits = atoi(optarg);
    
    break;
    
    case 'l':
    
    mode |= SPI_LOOP;
    
    break;
    
    case 'H':
    
    mode |= SPI_CPHA;
    
    break;
    
    case 'O':
    
    mode |= SPI_CPOL;
    
    break;
    
    case 'L':
    
    mode |= SPI_LSB_FIRST;
    
    break;
    
    case 'C':
    
    mode |= SPI_CS_HIGH;
    
    break;
    
    case '3':
    
    mode |= SPI_3WIRE;
    
    break;
    
    case 'N':
    
    mode |= SPI_NO_CS;
    
    break;
    
    case 'R':
    
    mode |= SPI_READY;
    
    break;
    
    default:
    
    print_usage(argv[0]);
    
    break;
    
    }
    
    }
    
    }
    
    
    int main(int argc, char *argv[])
    
    {
    
    int ret = 0;
    
    int fd;
    
    
    parse_opts(argc, argv);
    
    
    fd = open(device, O_RDWR);
    
    if (fd < 0)
    
    pabort("can't open device");
    
    
    /*
    
    * spi mode
    
    */
    
    ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
    
    if (ret == -1)
    
    pabort("can't set spi mode");
    
    
    ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
    
    if (ret == -1)
    
    pabort("can't get spi mode");
    
    
    /*
    
    * bits per word
    
    */
    
    ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
    
    if (ret == -1)
    
    pabort("can't set bits per word");
    
    
    ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
    
    if (ret == -1)
    
    pabort("can't get bits per word");
    
    
    /*
    
    * max speed hz
    
    */
    
    ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
    
    if (ret == -1)
    
    pabort("can't set max speed hz");
    
    
    ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
    
    if (ret == -1)
    
    pabort("can't get 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);
    
    
    while(1)
    
    {
    
    transfer(fd);
    
    sleep(1);
    
    }
    
    
    close(fd);
    
    
    return ret;
    
    }

Tony Liu

2016-10-26, Shenzhen

[http_www.wzaobao.com_p_l5079K.html]: http://www.wzaobao.com/p/l5079K.html
[http_www.emcraft.com_stm32f429discovery_accessing-spi-devices-in-linux]: http://www.emcraft.com/stm32f429discovery/accessing-spi-devices-in-linux
[http_blog.csdn.net_yuanlulu_article_details_6320740]: http://blog.csdn.net/yuanlulu/article/details/6320740