Detect NFC antenna connected to ST25DV04K

[Jignesh]

Hi,

We are using NFC tag IC ST25DV04K using I2C communication with our micro-controller.

Is there any way to detect, if the NFC antenna is connected or not to ST25DV04K using any I2C command?

Thank you in advance,

Jignesh Patel

[Brian TIDAL]

Hi,

is your question "is there a way to detect if the tag is currently in the RF operating volume of an NFC reader?" or is your question related to tag antenna being physically connected to the tag?

Rgds

BT

[Jignesh]

Hi @Brian TIDAL_O​ ,

Thank you for reply,

My question is related to check tag antenna being physically connect to the tag.

BR,

JP

[JL. Lebon · Accepted solution]

Hello,

The ST25DV04K is capable of detecting the presence of an RF field.

This detection is done by sensing the voltage on the 2 pins connected to the antenna.

A voltage above Vmin1 (see datasheet, it is 4.8Vpp between AC0/AC1 pins) is required. This is the minimum voltage to boot the tag.

The voltage on AC0/AC1 is created by having a current circulating in the antenna coil connected to AC0/AC1. A current circulates in the antenna if there is an RF magnetic field going through the antenna.

So, basically, checking if the antenna is physically connected to the tag means applying an RF field on the antenna and checking that there is a induced voltage on AC0/AC1.

This can be checked in the EH_CTRL_Dyn register by reading bit 2 FIELD_ON.

This can also be checked by enabling the GPO interrupt FIELD_CHANGE_EN. In that case, a pulse will be generated on the GPO pin as soon as there is a RF field strong enough to generate the Vmin1 (or stronger than 150mA/m).

This way you can check if the antenna is correctly connected the the tag's pins.

Best regards.

[Jignesh]

Thank you @JL. Lebon_O​ ,

We will check and update.

BR,

JP

[Brian TIDAL]

Hi,

just for my curiosity, can you share more information about your use case and about why you need to check the physical antenna connection? Is it for manufacturing/production tests?

Rgds

BT

[Jignesh]

Hi @Brian TIDAL_O​ ,

It's a part of system verification that is run on some time interval on Embedded system.

BR,

JP

[Jignesh]

@JL. Lebon_O​  @Brian TIDAL_O​ 

I have checked using EH_CTRL_Dyn register by reading bit 2 FIELD_ON. it detect the RF field if i take ST25DV04K near reader.

I want to detect antenna connected it self to ST25DV04K without reader.

Thank you,

Jignesh Patel

[Berenice BENVEGUDA]

Hello,

Trying to detect the antenna connection without a current circulating on the coils ( so having a RF field) is not possible from I2C interface

Best Regards,

BB