NFC T4T response timing SDK 15.3

RE: NFC T4T response timing SDK 15.3

Jefferson — Tue, 26 Mar 2019 19:29:11 GMT

I am getting the response data for NFC from BLE. I think the RF is bad on the other BLE device so it causes a long time for the data to arrive. I switched to getting data from UART and the NFC does not time out so I don't think there is any problem with NFC or BLE interrupts.

RE: NFC T4T response timing SDK 15.3

Kenneth — Tue, 26 Mar 2019 12:39:38 GMT

I have tried to ask around a bit, but I can not find any reason for what you are experiencing. The softdevice will only block the application for the amount of time specified in the corresponding softdevice specification (typically in the order of tens of us). I assume you have checked that if you close down the BLE link and/or use advertisement only you can confirm it is really related to BLE and not the delay itself.

RE: NFC T4T response timing SDK 15.3

Jefferson — Mon, 25 Mar 2019 20:25:46 GMT

I am using the NFC antenna that came with the PCA10040 and using USB power. Can BLE activity in the soft device block the NFC interrupt for more than 5ms? If I put the 6ms delay in the NFC_T4T_EVENT_DATA_IND event, it will block the NFC library from sending the S(WTX) and cause the timeout.

RE: NFC T4T response timing SDK 15.3

Kenneth — Mon, 25 Mar 2019 10:30:13 GMT

Hi,

I am not aware of anything no, the carrier frequency is significantly different between NFC and BLE, so I don't expect any problem. What NFC antenna&size have you used? Have you tried a larger antenna for comparison? What is the supply voltage here?

Best regards,
Kenneth

RE: NFC T4T response timing SDK 15.3

Jefferson — Fri, 22 Mar 2019 05:17:24 GMT

I am transferring some data over BLE while the reader is waiting for the response. Does BLE traffic interfere with NFC operations? I see the NFC_T4T_EVENT_FIELD_OFF event sometimes when I am transferring BLE data even though I am not moving the device away from the reader. I am using the PCA10040 board.

RE: NFC T4T response timing SDK 15.3

Kenneth — Thu, 21 Mar 2019 12:24:31 GMT

I think it will be a bit difficult to debug this. I assume you have checked that the reader here will expect a response within a certain time window, and you are fulfilling this requirement (e.g. 6ms may not work if it expect something else).

My suggestion here is that you add in addition an unpowered nRF52-DK as a simple sniffer here, by connect an NFC antenna to the unpowered nRF52-DK, and connect an oscilloscope probe as close as possible to the NFC pins on this unpowered kit. You should possible be able to sniff some activity between the reader and tag this way, by measure "something" during the NFC read and response (a change in voltage or similar that indicate the difference in timing), that may indicate that the timing you are trying to accomplish here actually is occurring as expected. Maybe if you have already a working setup you may compare the timing (the voltage will likely be different, but that doesn't matter).

Best regards,
Kenneth