I just opened the data sheet for the “Elec Freaks Ultrasonic Ranging Module HC-SR-04.” It needs editing, or the SparkFun description should include clarification. The data sheet explains:
The Echo is a distance object that is pulse width and the range in proportion. You can
calculate the range through the time interval between sending trigger signal and
receiving echo signal.
OK, software creates a 10 usec pulse, the eight sonic bursts leave the emitter, and then a TTL signal appears. Does the distance measurement relate to the time between the falling edge of the 10 usec signal and the leading edge (or falling edge?) of the Echo Pulse Output signal? Or is the width of the output pulse proportional to the the distance to an object? It’s not clear from the description. Better information and an improved timing diagram with added information would help people get off to an easier start. --Jon
