#include <stdio.h>
 #include <fcntl.h>
 #include <time.h>
 #include <unistd.h>
 #include <sys/ioctl.h>
 #include <linux/spi/spidev.h>

 static __u8 mode = 0x03;

 static int transfer(int fd_spi)
 {
     __u8 analogvalue;
     int ret;

     ret = read(fd_spi, &analogvalue, sizeof(analogvalue));
     if (ret<=0) {
         fprintf(stderr,"can't read analogvalue\n");
         return -1;
     } else
         printf("%d\n", analogvalue);
     return 0;
 }

 int main( int argc, char **arv, char **envp )
 {
     int fd_spi, ret;
     struct timespec sleeptime;

     fd_spi = open("/dev/spidev0.0", O_RDWR);
     if (fd_spi<0) {
         fprintf(stderr,"can't open
  /dev/spidev0.0\n");
         return -1;
     }
     ret = ioctl(fd_spi, SPI_IOC_RD_MODE, 	&mode);
     if (ret==-1) {
         fprintf(stderr,"can't set mode %d\n", mode);
         return -1;
     }
     ret = ioctl(fd_spi, SPI_IOC_WR_MODE, &mode);
     if (ret==-1) {
         fprintf(stderr,"can't set mode %d\n", mode);
         return -1;
     }
     ret = ioctl(fd_spi,
 SPI_IOC_RD_MAX_SPEED_HZ, 10000);
     if (ret==-1) {
         fprintf(stderr,"can't set rd-speed\n");
         return -1;
     }

     sleeptime.tv_sec = 0;
     sleeptime.tv_nsec= 250000000;
     while( 1 ) {
         transfer( fd_spi );
         clock_nanosleep(CLOCK_MONOTONIC,
 0,&sleeptime,NULL);
     }
     return 0;
 }