LPCD (Low Power Card Detection) works on the principle that the I and Q values are extracted from the RF signal captured on the RX pins. These values are then compared with the I and Q data obtained using LPCD calibration. If the difference is greater than the chosen I and Q threshold, the load is detected and the IC wakes up.
1// LPCD Way of working
- Run LPCD Calibration
- It is recommended to use an external power supply to supply the EVK board. If the USB supply is used, the value can fluctuate because of the transition effects.
- Run "Single LPCD" and check the performance
- Adjust the I and Q thresholds
- Low value -> Better detection range, more false wake-ups
- High value -> Worse detection range, fewer false wake-ups
The number of samples, RSSI, and VDDPA parameters typically remain at their default values.
2// Auto LPCD
When the "Auto LPCD" is used, the LPCD algorithm always performs LPCD Calibration before entering the LPCD.
3//Semi-autonomous LPCD mode (PN5190 only)
The user can evaluate the I and Q values behaviour under loaded/unloaded conditions. Based on that, the LPCD threshold can be properly selected.
- Use the same "Register" RSSI Target and Hysteresis as for "EEPROM"
- Calibrate LPCD
- Run "Endless I/Q read"
- Check how the I and Q values change
- With no card/object in the antenna proximity
- with a NFC card/object in the antenna proximity
