ST25DV16 reading issue

[plawat]

We programmed the ST25DV16 tag using the antenna and the GUI using the ST25R3919B. However, when we use the android apps to read the ST25DV16 tag its not getting read. The android apps read all the other tags of 13.56 mHz available in the market, but not ST25DV16 tag.

We are also able to charge the small battery of 24mAh connected to the ST25DV16 tag using the ST25R3919B as poller.

This tag is read using the GUI and the EVK of ST. How to make it work and be read by the android phone?

[JL. Lebon]

Hello, 

Can you please give some precisions on "The android apps read all the other tags of 13.56 mHz available in the market, but not ST25DV16 tag."?

- Does the application report the presence of the tag?

- What do you do to try to read the tag in the app?

- What is the content of the tag's memory ? (is there a NDEF? What is the CC File value ?)

- What version of Android are you using ?

Best regards.

[plawat]

NDEFEVK usedCC

1. Phone is one plus 8 pro, Apps used ST25, NFC tools, Taginfo
2. android version 13 used
3. ST Tag is not at all detected. The other tags (RFID cards - ISO 14443-3A) detected.
4. We progm the IC and then use this antenna to read the ST tag

[JL. Lebon]

Hello, 

When you say "not at all detected", I assume that even the UID is not reported by the application?

The tag antenna seems to be very tiny. Maybe the antenna is the reason why it is not detected by the phone when it is detected by the reader (which is more sensitive and powerful than a phone).

Can you provide characteristics of your antenna? (size, tuning frequency).

If you don't know how to measure the tuning frequency of the tag, it is explained in this application note: https://www.st.com/resource/en/application_note/an2972-how-to-design-an-antenna-for-dynamic-nfc-tags-stmicroelectronics.pdf (specially chapter 4 How to check the NFC/RFID dynamic NFC tag
antenna tuning). The tuning of the antenna must be measured with the ST25DV connected.

Best regards

[plawat]

Hi,

Yes, the UID is not reported too.

We are using the ST25DV16 as receiver and the ST25R3919B as poller. The antenna of these are fit to charge the smart ring battery of 24mAh. the antenna size are 11mm x 7mm as this fits the smart ring. We can not have a bigger antenna. Howevver we also tried to sense the tag using a bigger antenna :
bigger antenna

But still the tag is not sensed.

[JL. Lebon]

Hello, 

The size of the antenna is not the only factor.

As said above, you need to check the tuning in frequency of the antenna.

The antenna inductance must be around 4.8uH so that with the 28.5pF capacitance of the ST25DV, it will have a resonant frequency around 13.56MHz.

Do you know the inductance of the antenna and the tuning frequency of the couple antenna + ST25DV ?

Best regards.

[plawat]

Hi, We used this to design our antenna https://eds.st.com/antenna/#/
As the antenna was small with 12mm x 7mm we could achieve only around 500nH of inductance. However we could use the two ICs (poller - ST25R39 and listener ST25DV) to charge the device. We have 24mAh battery which we charge. Can we adjust the capacitance to match the frequency?

[plawat]

Listener has a inductance of 750nH, so we made this schematics. There is an additional 180pF in parallel to the charging coil.