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.emcraft.com/stm32f429discovery/accessing-spi-devices-in-linux

　　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