ST25DV04k NDEF message read/write error

[YLin.2]

Hi

I met a problem with reading/writing an NDEF message to ST25DV04k tag with iPhoneXR.

I will first introduce some background of the problem.

1. I use NFC Tools and NFC tap(ST) apps
2. When the tag is new, I used NFC Tools to write and read NDEF messages successfully
3. At some point, I wrote some bytes to the tag by NFC tap( I think the command is writesingleblock) and the NFC Tools can no longer write/read NDEF message to the tag.
4. Read/write bytes on NFC tap is always working fine.​
5. The area1 size is 512Byte
6. I looked up AN4911, and reset the CC bytes as E1 40 40 00 or E1 ​40 3F 00, but my phone still can not recognize the tag

My question is how to set up the ST25DV04k tag in order to be recognized as an "NDEF writable device"

Yuechuan

Best Regards

[Ulysses HERNIOSUS]

Hi YLin.2,

Could you share a memory dump? Using NFC tools / ST25 app?

Regards, Ulysses

[YLin.2]

hi

Here is the memory dump of a recognizable tag

And after I change block 1 to 0x12345678, the tag is no longer recognized as a NDEF tag.

To be specific, the app was searching for the tag indefinitely like below.

The CC file takes only 4byte, so it is fine to write at block 1, I suppose.

Yuechuan Lin

[Ulysses HERNIOSUS]

Hi Yuechuan Lin,

I think what you are asking are really specifics of the iOS parsing of NDEF. With writing 0x12345678 you create an invalid NDEF TLV which seems to be denied by iOS.

I am not sure if those details are documented. Maybe @victor laraison_O​  can provide further hints here.

Regards, Ulysses

[victor laraison · Accepted solution]

Hi All,

Ulysses is right : with iOS NDEF CoreNFC protocol, the iOS checks that block1 is valid and contains a valid NDEF TLV. This is why, when you use "Read NDEF" button, you are not able to detect anything.

The backup solution for Type5 tag is described as follow :

1. Hit “Read Tag�? button on Home Page => You select the iso15693 coreNFC Protocol.
   1. When Tag is detected , go in “More�? Tab Menu , then select “Area Content Editor�?. Normally, you will see the message “No NDEF message or Unknwon….�? 
   2. Click on Area1 => this opens a new screen for editing NDEF Record.
   3. Swipe the cell from Right to Left, then select “Add�? . A list of NDEF Record is displayed….
   4. Select your record (ex : NDEF Uri), then configure it, then hit button “Validate�? => This adds your new NDEF Record into the list of Records.
   5. Hit button “Write To Tag�? to write NDEF => This automatically updates the CCFile , and write NDEF record in Tag !!! 

I know, it is not very simple or user friendly.

We have currently an action for fixing this issue and next tiOS NFC Tap should contains something simpler.

But you have to know that in NDEF CoreNFC protocol, Type5 TAG must contains a valid CCFile + TLV for reading NDEF.

Moving to iso15693 coreNFC Protocol gives us more flexibility !!!

Hope it clarifies and helps.

BR,

[YLin.2]

Thank you.
I revived my st25dv using your method.
And I have also discovered earlier that I need to write TLV after the CC.
The ios app is very helpful comparing with android version.
But, I have to complaint about the FTM functionality in the app. The buffer write box requires hex input and buffer read box display data in hex, but there is no clear indication except a pop window telling me that it requires even characters! I wasted lots of time to figure this out.
I hope the FTM functionality in the app can be more clear about data format.
Yuechuan Lin

[victor laraison]

Thx Yuechuan for your feedback.

Regarding FTM User Interface, I take your point and put it into our backlog for next iOS NFC Tap Version.

Thx and br,

Vincent