Using CLRC663 and problem with LPCD while enabling CHARG PUMP

[mehanfar]

Hello to anyone reading this topic and issue related to that. Before hand I appreciate any feedback helping me resolve my problem. Now here is the case and problem:

I'm using CLRC663 to read MIFARE series and ISO15693 cards by enabling LPCD in the reader. I also am using interrupt pin to detect RF signal existence while in standby mode. I'm enabling LPCD filter and everything is fine with interrupt line and I receive interrupt when card is close to antenna (almost half of an inch or +1 cm from antenna). Since this distance is somehow short for my need I tried enabling CHARG PUMP feature in code. Fortunately this feature increase presence detection distance significantly. However, adversely it cause receiving wakeup interrupt over and over as soon as it goes in LPCD mode. This means to me that reader detects RX signals during RF ON period of CARD detection.

I tested this with filter enabled/disabled, different timing of LPCD RF On timeout on TIMER3 but no luck.

I appreciate if anyone can help me with that if had similar experiences.

Thanks

[danielchen · Accepted solution]

Hi

For CLRC663 LPCD, I would suggest you refer to AN11783:  CLRC663 plus low power card detection

You can download this application note from below link

https://www.nxp.com.cn/docs/en/application-note/AN11783.pdf

For your question , if you get unwanted interrupts.  maybe you can  reconfigure the thresh hold value to see whether it works

[mehanfar]

Thanks a lot Daniel for your time and information.

I'd gone through AN11783 and the more complete one AN11145 already. I also went through the whole document of CLRC663, read few threads, studied and tested NXP complete library and worked with NFC Cockpit as well during implementation and recently and here is what I found.

Unfortunately information provided in documents and library is insufficient. Moreover, for the key parts like I, Q channel behavior and how they are affected in loaded and no load condition there is not enough helpful information. Furthermore,  you can see misleading discrepancy between NXP library and AN11145 and NFC Cockpit and here is how:

While calibrating and reading I and Q Values:

In AN11145, section 3.2.1 Reading I and Q values, there is a sample code which works indeed. This code does not utilize charge pump and when enabling LPCD it does not enable Standby bit. Now, when you enable charge pump you will read two different values for I and Q if you enable or disable standby bit while executing LPCD command, This is the door that all issues come in. For example if you disable standby bit I=34, Q=24 and if you enable standby bit you read I=28 and Q=42. This is very big difference and cause all subsequent problems I face.

Now, after reading calibration values with disabled standby bit (default suggestion) when you go and set all registers and ask for LPCD with Standby mode, immediately you receive RF interrupt because I channel is set to 35 with threshold and Q channel to 24 but detected values during LPCD|STB are 28 and 42 so it causes to send LPCD interrupt. This will not happen if you calibrate with STB bit enabled. In summary there has to be complete similarity between calibration method and going to LPCD mode.

I've seen other differences between Cockpit default settings and NFC library and documents which are out of this discussion.

Thank you again.

[Geo65]

i totally agree about the problems faced during the reading and analyzing of the documents, not only some of data is inefficient but also misleading and somewhere .. wrong.

What Microcontroller are you using and did you find a solution for your problem.

Do you mind sharing a snippet of your code on how did you manage to enable the LPCD ?