Learn Robotics Programming

Reading an ultrasonic distance sensor

To be able to write code for the distance sensor, we will need to look at a few areas of its operation. As suggested previously, this system works by bouncing sound pulses off of objects, and timing their travel time.

A pulse is used on the trigger pin to ask for a sound pulse and timing to be sent. 10 microseconds is this pulse length, that is, 0.00001 seconds:

The echo pin responds by returning a pulse with a length corresponding to the sound travel time. The following diagram shows the timing of these:

Timing of a pulse and the response for an HC-SR04 distance sensor

By measuring the time between the ...