I've got the HC-SR04 ultrasonic distance sensor. I looked up online but was only able to find those Arduino tutorials to make it work. Here is one example.

http://www.alt42.com/2011/12/hc-sr04-ultrasonic-distance-sensor/

I'm wondering how to implement this particular function which is available in Arduino ? Basically it's measuring the duration that input pin voltage changes from high to low (vice visa), to calculate the distance (d = v*t/2).

    //get the time to receive rebound
    duration = pulseIn(us_echoPin, HIGH);

Hi victor -

Here is a forum thread lukel started to help him with a distance sensor. Hope it helps.