i2c测试

int main(int argc, char **argv)  

{  

    struct i2c_rdwr_ioctl_data e2prom_data;  

    unsigned int fd;  

    unsigned int slave_address, reg_address,value;   

    //slave_address为eeprom的地址，reg_address为eeprom中存储单元的地址，范围0x0--0xFFFFFFFF,value为你要写进eeprom的值  

    int ret;  

        

    if (argc < 5){  

        printf("Usage:\n%s /dev/i2c/x start_addr reg_addr value\n",argv[0]);  

        return 0;  

    }  

        

    fd = open(argv[1], O_RDWR);  

        

    if (!fd){  

        printf("Error on opening the device file\n");  

        return 0;  

    }  

        

    sscanf(argv[2], "%x", &slave_address);  

    sscanf(argv[3], "%x", &reg_address);  

    sscanf(argv[4], "%x", &value);  

        

    e2prom_data.nmsgs = 2;//因为都时序要两次，所以设为2  

    e2prom_data.msgs = (struct i2c_msg *)malloc(e2prom_data.nmsgs * sizeof(struct i2c_msg));  

    if (!e2prom_data.msgs){  

        printf("Memory alloc error\n");  

        close(fd);  

        return 0;  

    }  

        

    ioctl(fd, I2C_TIMEOUT, 2);//设置超时时间  

    ioctl(fd, I2C_RETRIES, 1);//设置重发次数  

        

    /* write data to e2prom*/  

    e2prom_data.nmsgs = 1;  

    e2prom_data.msgs[0].len = 2;//信息长度为2，看写时序，eeprom的地址不算的，因为付给了addr，而len是指buf中的值的个数  

    e2prom_data.msgs[0].addr = slave_address;  

    e2prom_data.msgs[0].flags = 0;//写命令  

    e2prom_data.msgs[0].buf = (unsigned char*)malloc(2);  

    e2prom_data.msgs[0].buf[0] = reg_address;//信息值1 eeprom中存储单元的地址，即你要往哪写  

    e2prom_data.msgs[0].buf[1] = value;//信息值2,即你要写什么  

        

    ret = ioctl (fd, I2C_RDWR, (unsigned long)&e2prom_data);//好了 ，写进去吧  

    if (ret < 0){  

        printf ("ioctl write error\n");  

    }  

        

    printf("you have write %02x into e2prom at %02x address\n",value,reg_address);  

        

    sleep(1);  

    /*read data from e2prom*/  

    e2prom_data.nmsgs = 2;//读时序要两次过程，要发两次I2C消息  

    e2prom_data.msgs[0].len = 1;//信息长度为1，第一次只写要读的eeprom中存储单元的地址  

    e2prom_data.msgs[0].addr = slave_address;  

    e2prom_data.msgs[0].flags = 0;//写命令，看读时序理解  

    e2prom_data.msgs[0].buf[0] = reg_address;//信息值  

        

    e2prom_data.msgs[1].len = 1;  

    e2prom_data.msgs[1].addr = slave_address;  

    e2prom_data.msgs[1].flags = I2C_M_RD;//读命令  

    e2prom_data.msgs[1].buf = (unsigned char*)malloc(1);  

    e2prom_data.msgs[1].buf[0] = 0;//先清空要读的缓冲区  

    ret = ioctl (fd, I2C_RDWR, (unsigned long)&e2prom_data);//好了，读吧  

    if (ret < 0){  

        printf ("ioctl read error\n");  

    }  

        

    printf("read %02x from e2prom address %02x\n",e2prom_data.msgs[1].buf[0], reg_address);  

        

    close(fd);  

    return 0;     

}