nRF52 write NFC Tag

[Alex]

Hi,

I am not yet familiar with NFC and have a question about using NFC with the nRF52.

If I understood it correctly the nRF52 is a "listening device" i.e. it cannot generate a NFC field and write data to another device. But is it possible to send/write data from another device (for example a smartphone) to the NFC tag of the nRF52. Or is it only possible to read data from the tag? If it is not possible at the moment will it be possible in the future?

I am using a nRF52 development kit with nRF5 SDK 11.0.0-2.alpha.

Thanks, Alex

[thln]

Hello,

The write NFC Tag is now enabled :)

I've removed the libnfc library because it didn't support the write feature, and no documentation is provided by Nordic to manage it. Furthermore the library gives information to the host (the NFC reader), that the card is NOT writable. So the host will never send the write request (0xA2).

What exactly does this library? It simulates a Type2 NFC buffer card, and provided data to the HAL driver. I've replaced it, by a function who sends the buffer content with the right datas.

static uint8_t Test_Memory_Type2[NFC_MAX_PAYLOAD_SIZE_RAW] = {
	// page 0
	0x5F, 0xF6, 0x4C, 0x6D,	// Internal 0-3
	0x2F, 0xF4, 0xDA, 0x59,	// Internal 4-7
	0x58, 0x03, 0x00, 0x00, // Internal 8-9 | Lock0-1       // <-- makes the card writable !
	0xE1, 0x11, 0x7C, 0x00, // CC0-3						// <-- makes the card writable !
	// page 4
	0x03, 0x16, 0xC1, 0x01,	// TLV Tag field, Length field, Value field
	0x00, 0x00, 0x00, 0x0F, // NDEF Payload length 15
	0x54, 0x02, 0x65, 0x6E, // NDEF Message Type : Text UTF8, "Hello World!"
	0x48, 0x65, 0x6C, 0x6C, //
	// page 8
	0x6F, 0x20, 0x57, 0x6F,
	0x72, 0x6C, 0x64, 0x21, //
	0x00, 0x00, 0x00, 0x00,
	0x00, 0x00, 0x00, 0x00,
};

I've linked directly the application calls to the HAL functions to check if it's working

ret_val = nfcSetup(nfc_callback, NULL);

replaced by ret_val = hal_nfc_setup(nfc_callback, NULL);

welcome_msg_encode(ndef_msg_buf, &len);
ret_val = nfcSetPayload( (char*)ndef_msg_buf, len);	

no need because the buffer is already set with the right datas

ret_val = nfcStartEmulation();

replaced by ret_val = hal_nfc_start();

So the main function looks like this below :

int main(void) {
	NfcRetval ret_val;

	printf("nfc_1 start\n");

	uint32_t err_code = NRF_LOG_INIT();
	APP_ERROR_CHECK(err_code);

	/* Configure LED-pins as outputs */
	LEDS_CONFIGURE(BSP_LED_0_MASK);
	LEDS_OFF(BSP_LED_0_MASK);

	ret_val = hal_nfc_setup(nfc_callback, NULL); // <-- callback to to application 
	APP_ERROR_CHECK(ret_val);

	// Start sensing NFC field
	ret_val = hal_nfc_start();
	APP_ERROR_CHECK(ret_val);
	while(1)
	{
		if (!NFC_NEED_MCU_RUN_STATE())
		{
			__WFE();
		}
	}
return 0;
}

And I've added the read & write command inside the NFCT_IRQHandler !

...
if (NRF_NFCT->EVENTS_RXFRAMEEND && (NRF_NFCT->INTEN & NFCT_INTEN_RXFRAMEEND_Msk))
{
    /* Take into account only number of whole bytes */
    uint32_t rx_data_size = ((NRF_NFCT->RXD.AMOUNT & NFCT_RXD_AMOUNT_RXDATABYTES_Msk) >> NFCT_RXD_AMOUNT_RXDATABYTES_Pos);

    nrf_nfct_event_clear(&NRF_NFCT->EVENTS_RXFRAMEEND);

	if (rx_data_size>NFC_CRC_SIZE) {
		rx_data_size -= NFC_CRC_SIZE;

		LOG_HAL_NFC("[NFC_HAL]: rx %02X [%02X]\r\n", m_nfc_rx_buffer[0], m_nfc_rx_buffer[1]);

        switch (m_nfc_rx_buffer[0]) {

        case T2T_READ_CMD :		// 30h
        	{
				uint8_t BNo = m_nfc_rx_buffer[1];
				if (BNo<252) /* Max Block number */
					hal_nfc_send(&Test_Memory_Type2[BNo*4], 16);
				else 
					/* hal_nfc_send(&Dymamic_Memory_Aera[0], 16); */
					hal_send_ack_nack(0x0);	// NAck
        	}
        	break;



        case T2T_WRITE_CMD :	// A2h
        	{
				uint8_t BNo = m_nfc_rx_buffer[1];
				if (rx_data_size==6) {
					LOG_HAL_NFC("[NFC_HAL]: receive");
					uint8_t i, c;
					for (i=0;i<4;i++) {
						c = m_nfc_rx_buffer[2+i];
						Test_Memory_Type2[BNo*4 + i] = c;
						NRF_LOG_PRINTF(" %02X", c);
					}
					NRF_LOG_PRINTF("\n");

					hal_send_ack_nack(0xA);	// Ack for write command
				} else {
					hal_send_ack_nack(0x0);	// NAck for write command : should be 0, 1, 4 or 5
				}
        	}
        	break;

        case NFC_SLP_REQ_CMD :
        	LOG_HAL_NFC("[NFC_HAL]: SLP_REQ\r\n");
        	m_slp_req_received = true;

        default:
        	/* Not a READ Command, so wait for next frame reception */
        	NRF_NFCT->TASKS_ENABLERXDATA = 1;
        	break;

        }
	}
...

the HAL send functions are listed below:

/**
 * send data to the host (the reader) with CRC16 
 */
hal_nfc_retval hal_nfc_send(const uint8_t *data, size_t dataLength)
{
	if (dataLength == 0)
	{
		return HAL_NFC_RETVAL_INVALID_SIZE;
	}

	
	/* Ignore previous TX END events, SW takes care only for data frames which tranmission is triggered in this function */
	nrf_nfct_event_clear(&NRF_NFCT->EVENTS_TXFRAMEEND);

	NRF_NFCT->PACKETPTR     = (uint32_t)(data);
	NRF_NFCT->TXD.AMOUNT    = (dataLength << NFCT_TXD_AMOUNT_TXDATABYTES_Pos) & NFCT_TXD_AMOUNT_TXDATABYTES_Msk;

	uint32_t reg = 0;
	reg |= (NFCT_TXD_FRAMECONFIG_PARITY_Parity << NFCT_TXD_FRAMECONFIG_PARITY_Pos);
	reg |= (NFCT_TXD_FRAMECONFIG_DISCARDMODE_DiscardStart << NFCT_TXD_FRAMECONFIG_DISCARDMODE_Pos);
	reg |= (NFCT_TXD_FRAMECONFIG_SOF_SoF << NFCT_TXD_FRAMECONFIG_SOF_Pos);
	reg |= (NFCT_TXD_FRAMECONFIG_CRCMODETX_CRC16TX << NFCT_TXD_FRAMECONFIG_CRCMODETX_Pos);
	NRF_NFCT->TXD.FRAMECONFIG  = reg;

	NRF_NFCT->INTENSET      = (NFCT_INTENSET_TXFRAMEEND_Enabled << NFCT_INTENSET_TXFRAMEEND_Pos);
	NRF_NFCT->TASKS_STARTTX = 1;

	LOG_HAL_NFC("[NFC_HAL]: send");
	uint8_t i;
	for (i=0;i<dataLength;i++) {
		NRF_LOG_PRINTF(" %02X", *(data+i));
	}

	NRF_LOG_PRINTF("\n");


	return HAL_NFC_RETVAL_OK;
}

/**
 * send a ack or nack to the host (the reader) without CRC16
 */
static hal_nfc_retval hal_send_ack_nack(uint8_t ack_nack_code) {
	static uint8_t Ack;
	Ack = ack_nack_code;

	nrf_nfct_event_clear(&NRF_NFCT->EVENTS_TXFRAMEEND);

	NRF_NFCT->PACKETPTR     = (uint32_t)(&Ack);
	NRF_NFCT->TXD.AMOUNT    =  4;

	uint32_t reg = 0;
	/* reg |= (NFCT_TXD_FRAMECONFIG_PARITY_Parity << NFCT_TXD_FRAMECONFIG_PARITY_Pos); */
	reg |= (NFCT_TXD_FRAMECONFIG_SOF_SoF << NFCT_TXD_FRAMECONFIG_SOF_Pos);
	NRF_NFCT->TXD.FRAMECONFIG  = reg;
	NRF_NFCT->INTENSET      = (NFCT_INTENSET_TXFRAMEEND_Enabled << NFCT_INTENSET_TXFRAMEEND_Pos);
	NRF_NFCT->TASKS_STARTTX = 1;

	return HAL_NFC_RETVAL_OK;
}

Et voila !

[thln]

Hi,

The sample code that I have published above is a simple way to have the write feature on nRF52. This code is not perfect, It's just first try ;) I've improve it and I' am writing the full nfc library to replace the Nordic one. For more informations to understand how it works, you can read the NFCForum Specifications.

NFCForum Digital Protocol found here : cwi.unik.no/.../NFC_forum_digital_protocol.pdf and NFCForum Type2Tag found here : apps4android.org/.../NFCForum-TS-Type-2-Tag_1.1.pdf

[Alvaro_Val]

Hi, I have been trying to find why do you use these  Internal Bytes  inside :   static uint8_t Test_Memory_Type2[NFC_MAX_PAYLOAD_SIZE_RAW] = { 0x5F, 0xF6, 0x4C, 0x6D, // Internal 0-3  0x2F, 0xF4, 0xDA, 0x59, // Internal 4-7 I have study the protocol and i dont understand why  do you use these bytes, and not others, if i use the ones that my  nfc Tag makes it doesnt support the write commands, and the nfc doesnt work. Could you explain to me, why do you use these particular and no others with different values? Best regards

[Alvaro_Val]

Hi, I mean i dont understand these: 0x5F, 0xF6, 0x4C, 0x6D, // Internal 0-3 0x2F, 0xF4, 0xDA, 0x59, // Internal 4-7 , the other bytes from the static uint8_t Test_Memory_Type2 i do understand. Thanks

[thln]

Hi, It's just the Device ID of my device. 0x5F, 0xF6, 0x4C, 0x6D, 0x2F, 0xF4, 0xDA, 0x59, 0x58 (with BCC).

You should replace it by your own device ID according to the : NRF_NFCT->NFCID1_LAST and NFCID1_2ND_LAST registers (for 7 bytes ID)

[david.drinn]

Thanks for this! How's it going in the past 2 years? Has it been working well? Thx again. :) Any chance a newer cleaned up version is available?