When using a PIR sensor in an application, it is necessary to allow the sensor some time to warm up. During warm-up the PIR sensor will reach equilibrium to the IR radiation in its current field of view and thus “learn” its environment to stabilize the output signal. During this time, it is important to keep the environment in the sensor's field of view undisturbed. The warm-up time can be adjusted in the application firmware by changing the define PIR_WARMUP_TIME_MS. While in warm-up, LED0 will flash at 1 Hz. When LED0 stops flashing, the warm-up is complete, and the system is now operating normally.
Waving a hand or walking in front of the sensor will now be detected and cause LED0 to flash at 4 Hz and will continue flashing as long as there is movement in the senor's field of view. When the movement stops, LED0 turns off.