Update NFC content on-the-fly

[Batov]

I want update NFC payload on-the-fly.

My test firmware based on nRF5_SDK_14.2.0_17b948a\examples\nfc\record_text (unable to update SDK. Legacy part.)

At firmware start:

/* Set up NFC */
err_code = nfc_t2t_setup(nfc_callback, NULL);
APP_ERROR_CHECK(err_code);

/* Encode welcome message */
err_code = welcome_msg_encode(m_ndef_msg_buf, &len);
APP_ERROR_CHECK(err_code);

/* Set created message as the NFC payload */
err_code = nfc_t2t_payload_set(m_ndef_msg_buf, len);
APP_ERROR_CHECK(err_code);

/* Start sensing NFC field */
err_code = nfc_t2t_emulation_start();
APP_ERROR_CHECK(err_code);

I am try update NFC payload:

err_code = msg_encode(m_ndef_msg_buf, &len);
APP_ERROR_CHECK(err_code);

err_code = nfc_t2t_payload_set(m_ndef_msg_buf, len);
APP_ERROR_CHECK(err_code);

nfc_t2t_payload_set is return NRF_ERROR_INVALID_STATE

Ok. I will call nfc_t2t_emulation_stop before update payload

err_code = msg_encode(m_ndef_msg_buf, &len);
APP_ERROR_CHECK(err_code);

nfc_t2t_emulation_stop();

/* Set created message as the NFC payload */
err_code = nfc_t2t_payload_set(m_ndef_msg_buf, len);
APP_ERROR_CHECK(err_code);

err_code = nfc_t2t_emulation_start();
APP_ERROR_CHECK(err_code);

That's working.

BUT I have next issue:

When I call nfc_t2t_emulation_stop, nfc_t2t_payload_set and nfc_t2t_emulation_start while tag at field(after NFC_T2T_EVENT_FIELD_ON) something went wrong and NFC tag unavailable for reader forever.

[Jørgen Holmefjord]

Hi,

Did you check the return code from call to nfc_t2t_emulation_stop? It may be that you cannot call these functions from interrupt context. Can you try to set a flag in the event handler, and do the payload update in the main context?

Best regards,
Jørgen

[Batov]

I have call nfc_t2t_emulation_stop from application context.

main.c

nfc_init("1", "2");
nrf_delay_ms(5000);
nfc_start("3");

nfc.c

static void nfc_callback(void * p_context, nfc_t2t_event_t event, const uint8_t * p_data, size_t data_length)
{
    (void)p_context;

    switch (event)
    {
        case NFC_T2T_EVENT_FIELD_ON:
            NRF_LOG_DEBUG("NFC_T2T_EVENT_FIELD_ON");
            break;
        case NFC_T2T_EVENT_FIELD_OFF:
            NRF_LOG_DEBUG("NFC_T2T_EVENT_FIELD_OFF");
            break;
        case NFC_T2T_EVENT_DATA_READ:
			NRF_LOG_DEBUG("NFC_T2T_EVENT_DATA_READ");
			break;
        case NFC_T2T_EVENT_STOPPED:
			NRF_LOG_DEBUG("NFC_T2T_EVENT_STOPPED");
			break;
        default:
            break;
    }
}

void nfc_init(char *p_fw_ver, char *p_hw_rev)
{
	NRF_LOG_DEBUG("NFC init");

	uint32_t  err_code;
	uint32_t  len = sizeof(m_ndef_msg_buf);

	err_code = nfc_t2t_setup(nfc_callback, NULL);
	APP_ERROR_CHECK(err_code);

	err_code = msg_encode(m_ndef_msg_buf, &len);
	APP_ERROR_CHECK(err_code);

	err_code = nfc_t2t_payload_set(m_ndef_msg_buf, len);
	APP_ERROR_CHECK(err_code);

	err_code = nfc_t2t_emulation_start();
	APP_ERROR_CHECK(err_code);
}

void nfc_start(char *test)
{
	NRF_LOG_DEBUG("NFC start");

	uint32_t  err_code;
	uint32_t  len = sizeof(m_ndef_msg_buf);

	err_code = nfc_t2t_emulation_stop();
	NRF_LOG_DEBUG("nfc_t2t_emulation_stop: 0x%x", err_code);

	err_code = msg_encode(m_ndef_msg_buf, &len);
	APP_ERROR_CHECK(err_code);

	err_code = nfc_t2t_payload_set(m_ndef_msg_buf, len);
	APP_ERROR_CHECK(err_code);

	err_code = nfc_t2t_emulation_start();
	APP_ERROR_CHECK(err_code);
}

logs with issue:

00> [00000000] <debug> NFC: NFC init
00> [00001374] <debug> NFC: NFC_T2T_EVENT_FIELD_ON
00> [00001491] <debug> NFC: NFC_T2T_EVENT_DATA_READ
00> [00005110] <debug> NFC: NFC start
00> [00005110] <debug> NFC: nfc_t2t_emulation_stop: 0x0

logs without issue:

00> [00000000] <debug> NFC: NFC init
00> [00003898] <debug> NFC: NFC_T2T_EVENT_FIELD_ON
00> [00004017] <debug> NFC: NFC_T2T_EVENT_DATA_READ
00> [00004402] <debug> NFC: NFC_T2T_EVENT_FIELD_OFF
00> [00005014] <debug> NFC: NFC start
00> [00005014] <debug> NFC: nfc_t2t_emulation_stop: 0x0
00> [00009423] <debug> NFC: NFC_T2T_EVENT_FIELD_ON
00> [00009541] <debug> NFC: NFC_T2T_EVENT_DATA_READ
00> [00009806] <debug> NFC: NFC_T2T_EVENT_FIELD_OFF

Issue: Unable to update NFC payload after NFC_T2T_EVENT_FIELD_ON event. Tag is unavailable for any readers.