Improve RF field st25R95

[emil28]

Hello,

I am working with a ST25R95 NFC reader. Everything works well, and I can read NFC tag using the library X-Cube-NFC3. I would like to improve the RF field strength with software. Is there a function in the library that I can use to improve the NFC reading ?

Thanks.

[Brian TIDAL · Accepted solution]

Hi Emilien,

Can you share more information about why you would like to improve the field strength? is it to increase the reading distance?

The field strength on ST25R95 is fixed for a given power supply voltage value and moving from 3.3V to 5V power supply does not improve the reading distance.

ST25R3911B and ST25R3916 readers have an higher output power. From software perspective, you can easily move from ST25R95 to ST253911B or ST25R3916 as the ST25R familly share the same RF Abstraction Layer API.

Rgds

BT

[emil28]

Hi Brian,

Thanks for your answer.

Yes, I would like to increase the reading distance. But it's not a problem if I can't improve it.

I am blocked on another problem, how can I put the ST25R95 in hibernate mode ? I can't find a function doing it in the NFC3 library.

Thanks.

[Brian TIDAL]

Hi,

can you clarify whether you need Tag Detection mode or real Hibernate mode and can you clarify your use case so that I can provide the most useful information?

RFAL in X-CUBE-NFC3 does not provide support for hibernate but to low power Tag Detection Mode. This low power tag detection mode is demonstrated in the polling demo of the X-CUBE-NFC3 when pressing the user button.

If hibernate is needed, you can copy the code from st25r95SPIIdle() function, copy the Idle[] array and modify its value.

Rgds

BT

[PKrig.1]

Hi @Brian TIDAL_O​ 

What is the best approach with the ST25R95 to achieve the highest reading distance? I'm using Type 5 Tags and require slightly longer read distance that I'm getting with the X-NUCLEO-NFC03A1 shield.

I see you mention that powering VPS_TX at 3.3V or 5V has no effect on the range? However in the data sheet it specifies that powering VPS_TX between 2.7V - 3.3V gives an output power of 55mW, and powering it between 4.5V - 5.5V gives an output power of 230mW? Am I misunderstanding that?

Is there a reference matching antenna circuit design for the ST25R95 when VPS_TX is at 5V? That would be very helpful to check this by changing the component values on the X-NUCLEO-NFC03A1 shield.

[Brian TIDAL]

Hi Peter,

this might sound counter intuitive but increasing the output power does not improve the reading distance (see explanation in https://community.st.com/s/question/0D50X00009XkXQOSA3/st95hf-error-code-8e and other posts related to ST25R95/CR95HF 5V supply in this community).

ST does not provide a reference matching circuit for 5V but supports customer with this configuration. The feedback from customers using 5V configuration is that this does not improve the reading distance and this is in accordance with ST internal testing at 5V.

Therefore, ST recommends to use 3.3V configuration.

Rgds

BT