This article describes how to evaluate ULPCD feature together with PN7642 EVK (OM27642EVK) and NFC Cockpit.
1// Disable DC-DC in EEPROM
OM27642EVK does not required any HW changes for ULPCD (**). User is only required to change the following settings in EEPROM (disable DC-DC converter).
Address: 0x0000 (Secure_Lib_Config)
Value: 0x21
Reset the board after writing the value.
**Note: To ensure an accurate and reliable ULPCD evaluation—particularly for ULPCD current measurements. We strongly recommend implementing the following hardware modifications on the OM27642EVK.
Note: New revision of the board already have R4=DNP, R8=0Ω. Kindly check this on your board.
2//Set required ULPCD settings in EEPROM
- ULPCD VDDPA -> Typically 1.5V. If the HF attenuator is 0x00, increase e.g. to 1.8V.
- Since the detection range does not significantly depend on the power level, there is no need to set VDDPA above 2 V. Higher VDDPA results in increased current consumption in ULPCD, but does not significantly improve detection performance.
- RF On Guard time -> This value can be reduced to the minimum -> 5.2 us
- RSSI Guard time -> Recommended value is 20-25
- Try different RSSI Guard Time settings and evaluate the RSSI jitter as described here. The objective is to identify the Guard Time that minimizes RSSI jitter, ideally achieving a variation of only 1 to 2 RSSI units.
- RSSI Threshold -> Typically 4~6
- Number of RSSI samples -> Typically -> 0 (4 rounds)
See an example bellow:
3// Perform "Reads HF Attenuator"
Once the required ULPCD settings is set (Guard times, Threshold....). Then User has to perform "Reads HF Attenuator". Make sure that the "HF Attenuator" option is checked.
As written above, the value must not be 0x00. If so, increase VDDPA.
4// Perform ULPCD Calibration and check RSSI Value
For OM27642EVK, the RSSI value for unloaded antenna is typically around 1400dec - 1600dec.
5//Enter ULPCD mode
User can enter the ULPCD mode. The board will again be connected once the load change is detected (e.g. NFC card or smartphone in the antenna proximity).
6// Typical detection performance for 65 mm x 65 mm Antenna tuned to 35Ω.
- MIFARE DESFire EV3: Class 1 Antenna
- ICODE SLIX: Class 1 Antenna
- ICODE 3: Class 6 Antenna
