   pinMode(pingPin3, INPUT);
   duration = pulseIn(pingPin3, HIGH);
   cm3 = microsecondsToCentimeters(duration);
-  
+ 
+ /* 
   // probe sensor 4
   pinMode(pingPin4, OUTPUT);
   digitalWrite(pingPin4, LOW);

  pinMode(pingPin4, INPUT);
  duration = pulseIn(pingPin4, HIGH);
  cm4 = microsecondsToCentimeters(duration);
 
  // output result on serial 
  Serial.print(cm1);


void loop()
{
  delayMicroseconds(50);
  
  // check for measurement request on UART
  if (Serial.available() > 0) {
    // read the incoming byte:
