Determine the end of an NFC Write?

RE: Determine the end of an NFC Write?

Michal — Tue, 07 Mar 2017 11:15:07 GMT

Good that your workaround seems to work.

The only issue I can see with using NFC_T4T_EVENT_NDEF_UPDATED is that UpdateNdefMessage might take long to execute and thus prevent from sending R-APDU (response to UpdateBinary) in time. This is because the callback for NFC_T4T_EVENT_NDEF_UPDATED event is called before sending the proper R-APDU. Other than that, I can't see why updating the NDEF content like you did originally, would not work, maybe some sniffer log could tell us more.

RE: Determine the end of an NFC Write?

CurtisHx — Mon, 06 Mar 2017 20:10:11 GMT

We came up with a work-around. We configured a hardware timer to fire its interrupt a few milliseconds after the last NFC_T4T_EVENT_NDEF_UPDATED event, and do all of the NDEF reconfiguration in there. That solved our problem.

RE: Determine the end of an NFC Write?

CurtisHx — Mon, 06 Mar 2017 16:48:15 GMT

It's consistent across phones. The NFC Tools doesn't read back the newly written content because the UpdateNdefMessage function writes over the NDEF buffer within the NFC Type 4 library.

RE: Determine the end of an NFC Write?

Michal — Mon, 06 Mar 2017 15:07:58 GMT

Then to me it looks OK on the nRF52 side. Regarding the phone side - is the error reported consistently on different phones? We have seen some variation between different phones, but generally NFC Tools seemed stable. Can the NFC Tools read back the newly written content even if reported an error on the Write operation?

RE: Determine the end of an NFC Write?

CurtisHx — Mon, 06 Mar 2017 14:54:59 GMT

The NDEF content is set as Read/Write. We get 2 NFC_T4T_EVENT_NDEF_UPDATED events every time we write. The data_length parameter is 0 on the first write, and is the written NDEF message length on the second write. The write operation is successful on the nRF52. However, the application side (we're using NFC Tools on Android phones) reports back with a generic write error.

RE: Determine the end of an NFC Write?

Michal — Mon, 06 Mar 2017 14:50:58 GMT

Let me add a couple of details regarding the NFC_T4T_EVENT_NDEF_UPDATED event:

it will only be triggered if the NDEF content was set as Read/Write i.e. using nfc_t4t_ndef_rwpayload_set - is it how you set it in your application?
the event is triggered each time the UPDATE_BINARY APDU is received with offset <= 1 (NLEN field)

Additionally, do you get any NFC_T4T_EVENT_NDEF_UPDATED event, e.g. when the Reader/Writer (PCD) clears the NLEN field? For short messages, some PCD could write NLEN together with the rest of the NDEF content (as part of a single UPDATE_BINARY Command APDU)

Also, is the write operation successful at all?

RE: Determine the end of an NFC Write?

CurtisHx — Thu, 02 Mar 2017 20:40:46 GMT

Unfortunately, neither one of those options work. The RXFRAMEEND event gets fired multiple times during a write, as does HAL_NFC_DATA_RECEIVED, and waiting for the last event (either one) doesn't work. I think what we'll have to do is start a timer on the last NFC_T4T_EVENT_UPDATED event, and update the NDEF record some timer after that last event. It's not a great solution, but it's a solution...

RE: Determine the end of an NFC Write?

FormerMember — Thu, 02 Mar 2017 09:10:39 GMT

Perhaps it is possible to use the event EVENTS_RXFRAMEEND directly from the NFCT peripheral or the event HAL_NFC_DATA_RECEIVED? I have not tested it, but it could be worth a try.