在spi应用中SPI_IOC_MESSAGE(1)和SPI_IOC_MESSAGE(2)，其中SPI_IOC_MESSAGE(2)为什么接收不到数据

蜗牛哦 2016-09-13 09:49:39

//---------------------------------------------------------------

参考源代码：

///////////////////////////////////////////////////////

#include <stdint.h>

#include <unistd.h>

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

#include <getopt.h>

#include <fcntl.h>

#include <sys/ioctl.h>

#include <linux/types.h>

#include <linux/spi/spidev.h>



static uint8_t  mode;

static uint8_t  bits = 8;

static uint32_t speed = 2*1000;         //32*100*1000; //500000;

static uint16_t delay=0;











#if 0

//read operating

static int transfer_r(int fd,unsigned short addr)

{

	int ret;

    unsigned char  cmd[2];

    unsigned char  databuffer[4];

    unsigned char  mydatabuffer[2];

	struct spi_ioc_transfer	xfer[2];

	

	



    

    cmd[0] = addr & 0x00ff; 

    cmd[1] = 0x80 | (addr >> 8); 

    memset(xfer,0,2*sizeof(struct spi_ioc_transfer));

    memset(databuffer,0x00,2);

    xfer[0].tx_buf          = (unsigned long)cmd;

    xfer[0].rx_buf          = NULL;

    xfer[0].len             = 2;

    xfer[0].delay_usecs     = delay;

    xfer[0].bits_per_word   = bits;	

    xfer[0].speed_hz        = speed;

        

    

    

    xfer[1].rx_buf          = (unsigned long)databuffer;

    xfer[1].tx_buf          = NULL;

    xfer[1].len             = 4;

    xfer[1].delay_usecs     = delay;

    xfer[1].bits_per_word   = bits;	

    xfer[1].speed_hz        = speed;

    





    ret = ioctl(fd, SPI_IOC_MESSAGE(2), &xfer);

	if (ret == -1 )

	    printf("can't transfer");



	printf("databuffer[0]=0x%x\n",databuffer[0]);

	printf("databuffer[1]=0x%x\n",databuffer[1]);

	printf("databuffer[2]=0x%x\n",databuffer[2]);

	printf("databuffer[3]=0x%x\n",databuffer[3]);



	return ((databuffer[1] << 8) + databuffer[0]);

}

#else

static int transfer_r(int fd,unsigned short addr)

{

	int ret;

    unsigned char  cmd[2];

    unsigned char  databuffer[4];

    unsigned char  mydatabuffer[2];

	struct spi_ioc_transfer	xfer[2];

	

	



    

    cmd[0] = addr & 0x00ff; 

    cmd[1] = 0x80 | (addr >> 8); 

    memset(xfer,0,2*sizeof(struct spi_ioc_transfer));

    memset(databuffer,0x00,2);

    xfer[0].tx_buf          = (unsigned long)cmd;

    xfer[0].rx_buf      = (unsigned long)databuffer;

    xfer[0].len             = 2;

    xfer[0].delay_usecs     = delay;

    xfer[0].bits_per_word   = bits;	

    xfer[0].speed_hz        = speed;

        



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

	if (ret == -1 )

	    printf("can't transfer");



	printf("databuffer[0]=0x%x\n",databuffer[0]);

	printf("databuffer[1]=0x%x\n",databuffer[1]);

	printf("databuffer[2]=0x%x\n",databuffer[2]);

	printf("databuffer[3]=0x%x\n",databuffer[3]);



	return ((databuffer[1] << 8) + databuffer[0]);

	

}

#endif

























int gv7601_read(unsigned char chip_id,unsigned short addr)

{

	int fd;

	int ret ;

    char device[1024];

	

    memset(device,0x00,1024);

    sprintf(device,"/dev/spidev1.%d",chip_id);

    fd = open(device,O_RDWR);

    if (fd < 0)

        printf("can't open device");



	/*

	 * spi mode

	 */

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

	if (ret == -1)

		printf("can't set spi mode");



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

	if (ret == -1)

		printf("can't get 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");



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

	if (ret == -1)

		printf("can't get 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");



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

	if (ret == -1)

		printf("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);	

		 		



    ret = transfer_r(fd,addr);

    close(fd);

	return ret;



}











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

{

    int tmp;



    while(1)

    {

        tmp = gv7601_read(3,0x06);

        printf("gv7601_read(1,0x06)=0x%x\n",tmp);

        sleep(1);

        

    

    }



    

    return 0;

    



}



问5：在spi应用中SPI_IOC_MESSAGE(1)和SPI_IOC_MESSAGE(2)，其中通过SPI_IOC_MESSAGE(2)为什么接收不到数据？

	//声明并初始化spi_ioc_transfer结构体

	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,

	};



	//SPI_IOC_MESSAGE(1)的1表示spi_ioc_transfer的数量 

	ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);		//ioctl默认操作,传输数据

	/////////////////////////////////////////////////////////////////////////////////////





    xfer[0].tx_buf          = (unsigned long)cmd;

    xfer[0].rx_buf          = NULL;

    xfer[0].len             = 2;

    xfer[0].delay_usecs     = delay;

    xfer[0].bits_per_word   = bits;	

    xfer[0].speed_hz        = speed;

        

    

    

    xfer[1].rx_buf          = (unsigned long)databuffer;

    xfer[1].tx_buf          = NULL;

    xfer[1].len             = 2;

    xfer[1].delay_usecs     = delay;

    xfer[1].bits_per_word   = bits;	

    xfer[1].speed_hz        = speed;

    





    ret = ioctl(fd, SPI_IOC_MESSAGE(2), &xfer);	





    为什么databuffer接收的数据全是0x00,用示波器测试接收脚有数据，如果通过ioctl(fd, SPI_IOC_MESSAGE(1)可以打印接收到数据