[NCS 2.6.1] NFC T4T response timing

[kartapusse]

Hi,

I am trying to use nfc_t4t_lib and I have some issues because processing incoming data takes some time (around 100 ms) and therefore sending the response occurs late after receiving the command.

There is a similar post but in my case, I am not using BLE at the same time, thus it is not exactly the same: devzone.nordicsemi.com/.../nfc-t4t-response-timing-sdk-15-3

If I have a delay (> 4 ms) after NFC_T4T_EVENT_DATA_IND, 

• nfc_t4t_response_pdu_send() returns success
• But reader receives 6E00 status word, although this is absolutely not the data I have sent with nfc_t4t_response_pdu_send()
• Moreover in the log, I observe the following error:

<err> nfc_platform: Tried to read data pointer: 4 bytes, read 0.
<err> nfc_platform: Reading nfc ring buffer failed, resetting ring buffer.

I was expecting the NFC T4T lib would send WTX to the reader until I call nfc_t4t_response_pdu_send() but it seems this is not the case. Am I missing something ?

Moreover, I was wondering: why NFC T4T library source code is not available ? Would it be possible to have access to it ?

Thanks and best regards,

Jean

[JONATHAN LL]

I was expecting the NFC T4T lib would send WTX to the reader until I call nfc_t4t_response_pdu_send() but it seems this is not the case. Am I missing something ?

You are not missing something. Will investigate internally. 


Proposal for possible workaround:

• set different FWI (Frame Wait Time) through nfc_t4t_parameter_set() to see if the possible race condition is resolved
• change the NFC callback processing: modify the IRQ priority of the callback or change the processing flow to use a dedicated thread instead of Work Queue: CONFIG_NFC_OWN_THREAD, CONFIG_NFC_THREAD_PRIORITY and maybe some others to see if it can help

Regards,
Jonathan

[kartapusse]

Hi,

Thanks for this first answer, I am waiting for your investigation concerning WTX that seems to be not sent.

I had already tested to set FWI to the maximum (8 if I have correctly understood) but this has no effect.

I just tested to change callback processing with CONFIG_NFC_OWN_THREAD and the behavior is the same on reader side. However the errors raised by nfc_platform that I have mentioned in my initial query are not raised in this configuration case. Thus, this configuration has an impact but it is not sufficient.

Regards,

Jean

[kartapusse]

Hi Jonathan,

Unless I missed an answer elsewhere, I am still waiting for the workaround. Do you have any info about it ?

Thanks and best regards,

Jean

[JONATHAN LL]

Hi Jean, 

kartapusse said:

I am still waiting for the workaround. Do you have any info about it ?

We are still waiting unfortunately, I am pining the developers here for you to try an push on this as we passed the 3 week timeline a few weeks back. Sorry for that. 

Understand your frustration and will keep you updated with any news. 

Regards,
Jonathan

[JONATHAN LL]

Hi Jean, 

A fix is added for the NCS 3.3.0 release and this should address the issue.  Sorry for this taking so long. 

Regards,
Jonathan

[kartapusse]

Hi Jonathan,

Thanks for the update, I will test this soon.

Correct me if I am wrong but 3.3.0 is not yet released ? Is the NFC fix already present in v3.3.0-preview1 version ? When 3.3.0 stable version will be released ?

Regards,

Jean

[JONATHAN LL]

kartapusse said:

Correct me if I am wrong but 3.3.0 is not yet released ?

Correct

kartapusse said:

Is the NFC fix already present in v3.3.0-preview1 version ?

It should be on the preview version yes, so you can test there to see if the issue still exist for you. 

kartapusse said:

When 3.3.0 stable version will be released ?

Not sure if we have a public release date, but I think you can expect it to be out before summer. 

Regards,
Jonathan

[kartapusse]

Hi Jonathan,

I have performed first tests with SDK 3.3.0-preview and the fix seems to work perfectly fine. I will soon extend my tests to ensure it fits to our needs but I am very confident now.

Thanks a lot for your support, it was worth the wait.

Jean

[JONATHAN LL]

Good to hear that it now works for you Jean, if there is anything else always feel free to reach out. We try to get things done in a reasonable amount of time but it can be difficult to do everything in a timely manner so sorry for the inconvenience it might have had. 

Regards,
Jonathan