#include <sys/time.h>
/* Headset button (AKA sensor) device file */
static const char *button_filename = "/sys/devices/platform/nokia-av/detect";

int read_button()
{
  FILE *fd;
  char button = 0;

  fd = fopen(button_filename, "r");
  button = fgetc(fd); // 4 is open, 2 (or 0 for hacked wiring) is closed
  fclose(fd);
  if (button == '4') return 0;
  else if (button == '2' || button == '0') return 1;
  else return -1;
}

int do_poll(int samples)
{
    int presses = 0, button_status, old_button_status = 0; // WARNING: Assuming button is open at start could lead to overcounting presses by 1/frame
    for (int i=samples; i > 0; i--)
    {
      button_status = read_button();
      if (!old_button_status && button_status > 0)  presses++; // No error checking
      old_button_status = button_status;
    }
    return presses;

int main(int argc, char **argv)
{
  struct timeval start_poll, end_poll;
  float elapsed_time;
  while(1) { // Begin main loop. This only exits if a trigger file that was specified is deleted.
    gettimeofday( &start_poll, NULL );
    presses = do_poll( 60 );
    gettimeofday( &end_poll, NULL );
    elapsed_time = (float)(end_poll.tv_usec - start_poll.tv_usec)/1000000.0;
    elapsed_time += end_poll.tv_sec - start_poll.tv_sec;
    printf("Revolutions: %i Elapsed: %0.2fs Hertz: %0.2f Approx. speed: %0.1fm/s\n", presses, elapsed_time, (float)presses/elapsed_time, presses*2.0/elapsed_time);
  } // End main loop
  return 0;
}