Here is simple Baseline design for interfacing PIR with the PSoC 3/5. The PIR sensor available on the CY3236A PIRMOTION EVK was used(PIR Motion Sensor, 3POS Mfg by: Glolab Corp. Mfg part no: PIR325). Few modifications were done on the EVK and external components were used. The topdesign of the project has the schematic.
Description: The output of the PIR sensor is sent to two low pass filters one with a cutoff of 0.03Hz and other with a cutoff of 30Hz. The lower cutoff filter was used an a reference for the one end of delta Sigma ADC( configured in differential mode) anmd the output of higher cutoff given to the other end. The signal is suitable sampled and the digital value compared with the baseline and the Threshold to signal the detection.
I am attaching the project. The project is well commented.