树莓派测试SPI接口

代码

/* 
 * SPI testing utility (using spidev driver) 
 * 
 * Copyright (c) 2007  MontaVista Software, Inc. 
 * Copyright (c) 2007  Anton Vorontsov <avorontsov@ru.mvista.com> 
 * 
 * This program is free software; you can redistribute it and/or modify 
 * it under the terms of the GNU General Public License as published by 
 * the Free Software Foundation; either version 2 of the License. 
 * 
 * Cross-compile with cross-gcc -I/path/to/cross-kernel/include 
 */  
  
#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();  
}

下面这段代码衔接到上面那段的后边(都放一个.c文里)

static const char *device = "/dev/spidev0.1";  
static uint8_t mode;  
static uint8_t bits = 8;  
//static uint32_t speed = 500000;  
static uint32_t speed = 20000000;  
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,  
        .rx_buf = (unsigned long)rx,  
        .len = ARRAY_SIZE(tx),  
        .delay_usecs = delay,  
        .speed_hz = speed,  
        .bits_per_word = bits,  
    };  
  
    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);  
  
    transfer(fd);  
  
    close(fd);  
  
    return ret;  
}

操作

1. 先用gcc编译

   gcc spidev_test.c

2. 将树莓派的MISO和MOSI引脚短接，运行命令

   sudo modprobe spi_bcm2835

3. 运行

   sudo ./a.out

如果SPI正常启用了的话，会出现以下结果：

否则会出现下面的结果：

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