树莓派SPI口测试！

用于测试树莓派的SPI接口是否正常工作，代码来自于

https://raw.githubusercontent.com/raspberrypi/Linux/rpi-3.10.y/Documentation/spi/spidev_test.c

测试方法参考自：http://louisthiery.com/spi-Python-hardware-spi-for-raspi/

 /*
  * SPI testing utility (using spidev driver)
  *
  * Copyright (c) 2007  MontaVista Software, Inc.
  * Copyright (c) 2007  Anton Vorontsov
  *
  * 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
 #include
 #include
 #include
 #include
 #include
 #include
 #include
 #include

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

 static void pabort(const char *s)
 {
     perror(s);
     abort();
 }

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

先用gcc编译

[plain]  view plain  c gcc spidev_test.c

得到一个a.out文件，后面会用到。

将树莓派的MISO和MOSI引脚短接，运行命令

 sudo modprobe spi_bcm2835

和

 sudo ./a.out

如果SPI正常启用了的话，会出现以下结果：

如果SPI没有连接或者有问题，则会出现以下结果：