M24SR and mobile phones compatibility

[serafim]

Hi. Is there a compatibility list of mobile phones and NFC chips, like M24SR?

I tried to connect to M24SR on my Samsung S6 - no luck! Same problem on latest Samsung and IPhone X.

However, Blackberry PRIV recongizes it.

May be, it is due to 14443-4 standard. 14443-3A tags are regognized easily on all mentioned phones.

Thanks, Serafim.

[JP Miller]

​Dear Serafim,

M24SR is an ISO/IEC 14443 tag up to layer 4. It supports device activation, readbinary, updatebinary and so on. We have tested it with Samsung and IPhone X phones and it works properly.

How the M24SR is configured affects the ability of the phone to read or not the tag content.

For example those phones expect to read NFC forum tags. M24SR needs to be programmed to have a NDEF file with no read protection .

Could you please explain a bit more what you are trying to do with M24SR and how it is being programmed (Capability container & System File specifically) so that we can further debug this problem?

Have a good day.

Regards

[serafim]

Thank you very much.

 After you answer I re-checked my workbench and found that it DOES CONNECT !! The problem was in long distance between antenna on my board and phone. 

https://www.st.com/en/evaluation-tools/b-l475e-iot01a.html

Indeed, the board has buttons with long actuators on one side and spacers on the other. I could not reach the antenna with my phone. when I removed spacers, the Tag was recognized by my phone.

However, my manually soldered board (see picture) does not work. The phone doesn't even write "Tag found with unsupported format" like it usually does with MIFARE tags.

Antenna is a commercially available one. 

https://www.digikey.com/product-detail/en/pulselarsen-antennas/W7001/553-2633-ND/4169647

I soldered it directly to pins 2 &3 of M24SR

What could be wrong with it? Could you suggest me what to do next? If possible, I would like to use some kind of commercially available antenna.

Best regards, Serafim

[JP Miller]

Dear Serafim,

In order to achieve the best operating distance between your phone and the tag, it is advisable to have a resonant frequency on the tag closed to or slightly higher than 13.56Mhz, the ISO14443 operating frequency.

​To achieve that, one needs to take into account the M24SR internal tuning capacitance which is centered on 25pF.

The antenna inductance is then calculated with the equation: L must be close to 5.5uH.

The antenna you have selected does not match that requirement (L=0.9uH), so the tag receives little energy from the phone, and can not work properly.

Please try to select another antenna with a L closer to 5.5uH. It should work better.

More information can be found in the following application note:

https://www.st.com/content/ccc/resource/technical/document/application_note/d9/29/ad/cc/04/7c/4c/1e/CD00221490.pdf/files/CD00221490.pdf/jcr:content/translations/en.CD00221490.pdf

Have a good day,

Regards,

[serafim]

Thank you for your reply.

You are right, the commercial antenna has low inductance, 0.9 uH.

I erroneously implied that it has proper inductance value. However, in datasheet they have shown proper LC layout.

https://media.digikey.com/pdf/Data%20Sheets/Pulse%20PDFs/Antennas_Catalog_Ver13.pdf

What do you think, the proposed in datasheet LC is necessary or a proper capacitor in parallel with the antenna will be sufficient?

Regards, Serafim

[JP Miller]

​Hello again,

In theory it is possible to add a capacitor in parallel to the one present in M24SR. But this value would be large for this antenna, with about 100pF extra. Usually such a capacitor will have a very large Q which has the effect of modifying the slope of the incoming signals to the tag and affect it negatively.

We optimally recommend that if possible in your design, you choose an antenna with an inductance value of around 4.7uH. That would match with the M24SR as is without matching network.

If not possible, at best, the external capacitance that can be added in parallel to the one in M24SR should be not higher than the M24SR one.

In combination it might be possible in your design to have 2 layers in antenna on top of each other, connected serially. That would double the inductance of the antenna, and reduce the external capacitance requirements.

As external capacitance quality factors vary, some experiments might be handy to find the proper set up. This is why we advise selecting the proper antenna from the get go as it makes the design easy.

Regards

[serafim]

Thank you. I will try with proper antenna.

Unfortunately, there are no antennas commercially available.

Regards, Serafim