Работа с SPI через ioctl

 int main(int argc, char **argv)
 {
         int fd = 0;
         char buff[32];
         char rbuff[32];  
 
         fd = open(PATH, O_RDWR, 0);
         if (fd == -1) {
                 perror("open error");
         }
  
         ioc_transfer.tx_buf        = (unsigned long)buff;
         ioc_transfer.rx_buf        = (unsigned long)rbuff;
         ioc_transfer.len           = 32;
         ioc_transfer.delay_usecs   = 0;
         ioc_transfer.speed_hz      = 1000000;
         ioc_transfer.cs_change     = 1;
         ioc_transfer.bits_per_word = 8;
 
         for(;;) {
                 int ret = ioctl(fd, SPI_IOC_MESSAGE(1), &ioc_transfer);
                 if (ret == -1) {
                         perror("ioctl error");
                         return -1;
                 }
 
                 usleep(1000000 / send_pack_freq);
         }
 
         return 0;
}