* Works with many different ultrasonic sensor models: HC-SR04, SRF05,
SRF06, DYP-ME007, JSN-SR04T & Parallax PING)))™.
* Built-in digital filter method ping_median() for easy error correction
(use SONAR_ITERATIONS build flag to configure).
* Allows setting of a maximum distance where pings beyond that distance
are read as no ping or clear (use SONAR_MAX_DISTANCE build flag).