Hello,
I'm using NFC Type 4 Tag (T4T) but I can't write to it. The tool I'm using is the nRF NFC Toolbox. From the app screen I generate a Record and then touch the tag to attempt a write,
but only "tag discovered" appears and no message indicating success is shown.
After a bit of investigation, the issue seems to occur after the tag side generates an NDEF message. Below is the source code that generates the message and record.
void binary_encode(uint8_t *buffer, uint32_t *len)
{
uint8_t data[6] = {0x00,0x01, 0x02, 0x03, 0x04, 0x05};
uint8_t id[2] = {0x00, 0x00};
int err;
NFC_NDEF_MSG_DEF(nfc_test_msg, 1);
NFC_NDEF_RECORD_BIN_DATA_DEF(nfc_tset_record,
TNF_EXTERNAL_TYPE,
id,
2,
NULL,
0,
data,
sizeof(data));
err = nfc_ndef_msg_record_add(&NFC_NDEF_MSG(nfc_test_msg),
&NFC_NDEF_RECORD_BIN_DATA(nfc_tset_record));
if (err) {
printk("Cannot add record!\n");
}
/* Encode whole message into buffer */
err = nfc_ndef_msg_encode(&NFC_NDEF_MSG(nfc_test_msg),
buffer,
len);
if (err) {
printk("Cannot encode message!\n");
}
err = nfc_t4t_ndef_file_encode(buffer, len);
if (err) {
printk("Cannot encode file!\n");
}
}In this source code I'm creating binary data as an NDEF message with the Type Name Format set to "External Type".
However, if I comment out the final nfc_ndef_msg_encode and nfc_t4t_ndef_file_encode calls, I can write using the app — the app shows "Tag written successfully". I understand those functions set the NDEF message into the buffer. Once the message is set, is it no longer possible to write?
Also, I confirmed that if I use a different Type Name Format instead of External Type, writing works normally. Below is the source code.
int welcome_msg_encode(uint8_t *buffer, uint32_t *len)
{
int err;
/* Create NFC NDEF text record description in English */
NFC_NDEF_TEXT_RECORD_DESC_DEF(nfc_en_text_rec,
UTF_8,
en_code,
sizeof(en_code),
en_payload,
sizeof(en_payload));
/* Create NFC NDEF message description, capacity - MAX_REC_COUNT
* records
*/
NFC_NDEF_MSG_DEF(nfc_text_msg, MAX_REC_COUNT);
/* Add text records to NDEF text message */
err = nfc_ndef_msg_record_add(&NFC_NDEF_MSG(nfc_text_msg),
&NFC_NDEF_TEXT_RECORD_DESC(nfc_en_text_rec));
if (err < 0) {
printk("Cannot add first record!\n");
return err;
}
err = nfc_ndef_msg_encode(&NFC_NDEF_MSG(nfc_text_msg),
&buffer[2],
len);
if (err < 0) {
printk("Cannot encode message!\n");
}
err = nfc_t4t_ndef_file_encode(buffer, len);
if (err) {
return err;
}
return err;
}The above uses the Well-known Type Name Format and generates text data as an NDEF message. I confirmed that with this, writing succeeds even if I do not comment out the encode calls.
I don’t understand why writing fails when the Type Name Format is External Type. Is there a restriction that prevents writing after an External Type message has been created? Also, could the app be imposing a restriction on External Type writes — I’d like to know if that’s possible.
If you notice any mistakes or issues in the source code above, please let me know.
cpu:nrf5340
zephyr:3.5.99
sdk 2.6.0
NFC:T4T
borard:nrf5340dk
best regards.
