树莓派linux之间如何用SPI通信？求大神

tt1995cc 2019-10-23 10:11:09

自发自收没有问题，但两个树莓派之间spi收发数据无法成功，我怀疑是否是linux默认为主设备，两个主设备无法通信？？？但从原理分析应该可以收到数据才对，即一个发，一个收，应可以收到才对，但依然不行，代码如下：



#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>



#include <string.h>



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







static void transfer(int fd);



static void pabort(const char *s);







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



static uint8_t mode;



static uint8_t bits = 8;



static uint32_t speed = 80000;



static uint16_t delay;



static uint8_t cs = 1;



//缓存区



char tx[10]= "1234";



//uint8_t tx[1800]= {100,101,102,103,104};



char rx[ARRAY_SIZE(tx)] = {};







int spi_init()



{



    int ret = 0;



    int fd;



  //  mode = mode | SPI_MODE_0 | SPI_CS_HIGH | SPI_LSB_FIRST | SPI_LOOP;



    //parse_opts(argc, argv);



//step 1 open



    fd = open(device, O_RDWR);



    if (fd < 0)



        pabort("can't open device");



//step 2 ioctl cmd



    /*



     * spi mode



     */



    ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);//写模式



    if (ret == -1)



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



    ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);//读模式



    if (ret == -1)



        pabort("can't get spi mode");



    /*设置或获取SPI读写数据位数



     * bits per word



     */



    ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);//写 每字多少位



    if (ret == -1)



        pabort("can't set bits per word");



    ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);//读 每字多少位



    if (ret == -1)



        pabort("can't get bits per word");



    /*



     * max speed hz



     */



    ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);//写 最大速率



    if (ret == -1)



        pabort("can't set max speed hz");



    ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);//读 最大速率



    if (ret == -1)



        pabort("can't get max speed hz");



    



    return fd;



}



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



{



    int fd = spi_init();



    int flag = 0;



    printf("spi fd:%d\n",fd);



    printf("spi mode: %d\n", mode);



    printf("bits per word: %d\n", bits);



    printf("max speed: %d Hz (%d KHz)\n", speed, speed/1000);



//step 3  read and write



    while(1){



        if(getchar() == '1'){



            flag = 1;strcpy(tx,"1234");



        }



        else if(getchar()=='2'){



            flag = 1;strcpy(tx,"2345");



        }



        if(flag)



            transfer(fd);



        if(strlen(rx)>0)



        {



            printf("Recv:%s  , len %d\n",rx,strlen(rx));



           // printf("recv:%d,%d,%d,%d,%d",rx[0],rx[1],rx[2],rx[3],rx[4]);



        }



        printf("--");



        //printf("recv:%d,%d,%d,%d,%d",rx[0],rx[1],rx[2],rx[3],rx[4]);



    }



//step 4 close



    close(fd);



    return 0;



}



//传输函数



static void transfer(int fd)



{



    int ret;



    



	//全双工传输数据



    struct spi_ioc_transfer tr = {



        .tx_buf = (unsigned long)tx,



        .rx_buf = (unsigned long)rx,



       // .len = ARRAY_SIZE(tx),



        .len = 5,



        .delay_usecs = delay,



        .speed_hz = speed,



        .bits_per_word = bits,



        .cs_change = cs



    };



    ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr); // SPI_IOC_MESSAGE(n) 表示传输n个数据包 



    if(ret < 1)



        pabort("can't send spi message");



}



static void pabort(const char *s)



{



    perror(s);



    abort();



}