USB PIR Motion Detector Passive Infra-Red Module in a tiny enclosure
The CGUSPPIR module assembly is a motion detector that identifies as a U421. The module detects changes in the field of infra-red that it "sees", and interprets that as motion. The sensor has a range of about 20 feet.
The PIR module performs a self-calibration on powerup that lasts up to 40 seconds. During this period it is important to provide the sensor with as little motion or change in environment as possible.
Read Port A bit 5 in order to read the PIR status. The pin is normally low, motion makes it momentarily high.