ST25R3916B Passive Target Sample Code

[LltWc]

Is there any example code for ISO14443A passive target mode, which is supported on the ST25R3916B? I'm prototyping basic functionality before fully implementing our application, and it would be nice to do a proof of concept without having to grapple with the RFAL. I'm using the X-NUCLEO-NFC08A1 with an STM32L476RG_NUCLEO.

To that note, if there are any instructions on using the RFAL (which headers to modify, any other configurations to set), I would appreciate being pointed to them.

[Ulysses HERNIOSUS]

Hi LltWc,

ST25 Embedded NFC lib contains a pairing example project which presents and NDEF on an emulated T3T/T4T to e.g. a mobile.

Ulysses

[LltWc]

Got it, I just tried that out. I'm specifically seeking to test passive target mode, in which the ST25R3916B acting as PICC without an external power source will respond to a phone or other NFC device acting as PCD initiating a connection. That pairing example did pull up a Bluetooth pairing request, but only when the ST25R3916B was powered. Is there an example project that will show that passive target mode functionality?

[Ulysses HERNIOSUS]

Unfortunately ST25R3916 is a reader chip with additional tag emulation functionality. It cannot work from harvested power. You should be looking at a tag chip: ST25DV or ST25TA or ST25TV.

BR, Ulysses

[LltWc]

Could you clarify what ISO/IEC 18092 Passive Target mode actually means then? That document describes passive communication mode as the Initiator generating the RF field, and the Target responding in a load modulation scheme—isn't the whole point of the load modulation scheme to be operable without a power supply?

Does ST offer a chip that can operate as a tag reader and tag with harvested power? My use case is for a device that will scan multiple tags that store IDs, then that same device will be scanned by a reader hours or days later, when the battery may be exhausted. Two different chips would significantly increase complexity.

Lastly, what search terms should I be looking for to find a chip that will operate as a tag with harvested power? Does the NFC Forum define a specific name/term?

[Brian TIDAL]

Hi

clause 4.18 of the ISO/IEC 18092 defines the Passive Communication Mode. ISO/IEC 18092 defines as well Initiator (clause 4.7) and Target (4.23). But Passive Target mode is not defined in the ISO/IEC 18092. This is an ambiguous terminology. This is a device acting as a target in passive communication mode.

Having passive communication mode defining that the Target responds in a load modulation schemes does not imply that the target operates without a power supply. 

NFC readers are devices operating with a power supply; when they are configured in Card Emulation mode they are still operating with a power supply.

If your device is a tag storing ID, why does a power supply is needed? Maybe what you need is simply a dynamic tag such as ST25DV. Feel free to explain in more details your use cases.

Rgds

BT

[LltWc]

The intention is to have a device that can scan NFC tags to store IDs, then be out in remote operation for a period of hours to days without necessarily being recharged. When the device is found, still out in the field and out of power, it should still be possible to read the list of IDs without having to recharge it. The device includes other functionality that will use the battery much more quickly than NFC.

The complication is that I require both NFC reader and NFC energy-harvesting tag functionality. The ST25DV is only an NFC tag. While it's possible to include separate reader and tag chips, it would increase design complexity, so I would prefer to avoid that.

[Ulysses HERNIOSUS · Accepted solution]

Hi,

I am not aware that what you are looking for actually exists. For sure NFC Forum does not define such devices (Reader with harvested power tag emulation).

I think mobiles are implementing a similar functionality to what you are describing by never completely draining the battery to be still able to support card emulation for some extended time. I think this is needed for things like having your Car Key on the mobile, etc.

Ulysses

[LltWc]

I just spent a while researching and that does seem to be correct; most competitor chips have similar operation to the ST25R3916B. (Except an old MediaTek chip for some reason! The MT6605 looks like it would work, but it's not even mentioned on the MediaTek website so that's not feasible.) I'll have to discuss options with my team, thanks for your help.