/*****************************************************
* function void range() measures range to an object  *
* using the SRF04 sonar ranging sensor.  It displays *
* range on the LCD display in mm, and sounds a tone  *
* proportional to the range (higher is closer).      *
*****************************************************/

#use "srf04_sonar.ic"

void range()
{
    int d, freq, a=-4, b=4200;
    float duration=0.1;
    
    printf("Press START...");
    while (!start_button())
      ;
    while(!stop_button()) {  /* Loop forever */
        d = sonar();  /* Get distance in mm */
        printf("D=%d mm\n",d);
        freq = a*d+b;  /* Compute frequency */
        if (freq < 200)
          freq = 200;
        if (freq > 4000)
          freq = 4000;
        tone((float)freq,duration);  /* Play tone */
        sleep(0.03);
    }
    printf("\n");  /* Clear display */
}