ISO 14443-4 Reading issue

Question

suleman_khalid OP

Created May ’25

Replies 3

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Participants 3

I am working with a Texas Instruments RF430 NFC tag, which is compliant with:

ISO/IEC 14443-4 (ISO-DEP) NFC Forum Type 4 Tag NFC-B protocol NDEF-formatted storage

I’m using an iPhone 12 running iOS 18, and my app uses the Core NFC framework.

Using NFCNDEFReaderSessionDelegate, I am able to successfully read the first NDEF message from the tag. However, the tag stores multiple NDEF messages, and I would like to access the others. Based on the tag’s specification, these messages are accessible via an NDEF file located at file ID 0xE104.

To try and access this additional NDEF file, I attempted to use NFCTagReaderSession with the NFCTagReaderSessionDelegate, intending to issue APDU commands. However, the tagReaderSession(_:didDetect:) delegate method is never called, even though the tag is present and detected using NFCNDEFReaderSession.

My questions:

Does Core NFC on iOS 18 support issuing custom APDU commands to ISO 14443-4 (NFC-B) tags like the TI RF430?

Is the use of NFCTagReaderSession with NFC-B fully supported for tags that implement ISO-DEP (even if they are NDEF-formatted)?

Is there any known limitation or configuration required to ensure tagReaderSession(_:didDetect:) is triggered for NFC-B/ISO-DEP tags?

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Answer 1

Engineer OP

Apple

Jun ’25

Core NFC supports NFC-B and reading multiple messages from NDEF tags.

Are you setting invalidateAfterFirstRead to FALSE in your NFCNDEFReaderSession's initWithDelegate method?

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Answer 2

SaiSwaroop_87 OP

1d

attempting to switch to NFCTagReaderSession to communicate at the ISO-DEP / APDU level fails silently. The tagReaderSession(_:didDetect:) delegate is never called, even though the same physical tag is clearly present and readable via the NDEF session.

From my observation, it appears that on iOS, once a tag is handled as an NDEF Type 4 tag, Core NFC does not reliably expose it again through NFCTagReaderSession for raw ISO-DEP / APDU communication—especially for NFC-B tags. The session starts successfully but does not surface the tag for APDU exchange.

This raises an important question: Is there any supported way on iOS to reliably issue custom APDU commands to ISO 14443-4 (NFC-B) tags like the TI RF430, or is APDU access effectively restricted/filtered by Core NFC when the tag is NDEF-formatted? If this is a platform limitation, it would be helpful to have clarity on whether iOS intentionally blocks APDU-level access for such tags.

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Answer 3

Engineer OP

Apple

17h

I believe the explanation at https://developer.apple.com/forums/thread/792910 will answer your question here as well.

0