AN-000226 – CH201 Ultrasonic Presence Detection Reference Design User Guide

Motion detectors are electrical devices that use sensors to detect nearby motion. Such devices are often integrated as system components that automatically generate alerts when motion is detected in an area. These detectors are vital components of security and surveillance systems, automated lighting control, energy efficient systems, and other management systems. They can also enhance public and home safety by automatically triggering smart locks, smart doorbells, and other home and building automation systems.

This document details the specification, the programming and operation of a CH201 ultrasonic senor and M0 MCU Module Reference Board. This module reference board incorporates a M0+ ARM Core IC and a CH201 Ultrasonic Sensor with acoustic housing assembly. When programmed with Chirp’s Presence Detection firmware, the module shall operate as a motion detection device, signaling the detection of motion via a GPIO line.

Chirp provides two presence sensing algorithms that can be used in different scenarios: Presence Detection and Static Target Rejection (also known by its acronym, STR). Each algorithm has specific strengths. See the Presence Detection App Note, AN-000214, for discussion on the benefits and tradeoffs of each algorithm. This application note will document the Presence Detection algorithm’s usage in a complete reference design module.