while (1)
{
  char buffer[40]; /* buffer to accumulate DMM chars in */
  DWORD now;
  int n,cnt;
  /* Set up interval to wait for next sample */
  next_read+=gSampleInterval;
  now=TimeTick;
  if (now <next_read)
    OSTimeDly(next_read-now);
    /* An RTOS function that yields for some number of ticks */
  else
    next_read=TimeTick;
  write(fddvm,"\r",1); /* Ask DVM for a new sample */
  cnt=0;
  /* Read data from DVM */
  while(1)
  {
    n=ReadWithTimeout(fddvm,buffer+cnt,40-cnt,TICKS_PER_SECOND);
    if (n <=0)
    {/* DVM is probably off */
      next_read=TimeTick+gSampleInterval;
      DVMState=DvmDead;
      break;
    }
    else
    {
      cnt+=n;
      buffer[cnt]=0;
      if (buffer[cnt-1]=='\r')
      {
        if ((strncmp(buffer,"TEMP",4)==0))
        {/* Last DVM reading was a Temperature */
          int t;
          t= atoi(buffer+5);
          DVMState=DvmOk;
          StoreSample(t);
        }
        else
        {
          DVMState=DvmSetWrong;
        }
        break;
      }
    }
  }/* While reading */
}/* While forever */

Listing 1—This code gathers samples from the DVM and stores them in a circular buffer. It also detects errors in the DVM connectivity 
                 and settings.