ST25R3916 NFC RFID - Phone Detection

[berkayCinci]

Hello,

Is it possible to detect a phone using NFC/RFID readers?

I am working on a wireless charger unit and trying to detect credit cards. When I put a mobile phone with a credit card, I am not able to detect credit card because phone is getting started to charge. I want to learn whether it is possible to detect phone using ST25 NFC Readers. 

Is it possible to read Q value of NFC side? After we talked with the vendor of power transmitter, he suggested us to read Q value of NFC side. 

[Ulysses HERNIOSUS]

Hi,

if tag and phone enter at the same time then RFID should detect the card and prevent Qi operation, right?

Ulysses

[yusufekici]

Hi Ulysses,

Yes, that's what we want to do.

[Ulysses HERNIOSUS]

Hi Berkay,

Are you fine with the explanations: Always perform NFC polling (rfal_cd) before Qi to avoid damage to pure NFC cards.  This should also handle the case of both being brought together into the field.

BR, Ulysses

[yusufekici]

Hi Ulysses,

I am ok with performing NFC polling before Qi to avoid damage.

However I need a mechanism to initiate NFC polling via a phone placed on the NFC. If no RFID tag is detected, the charger should proceed to the Qi state. If I simply poll for an NFC check and then move to the Qi state, there is a risk that the charger might enter the power transfer phase before detecting an RFID card. Therefore, we need an initiator (phone detection) to start this process.

[Ulysses HERNIOSUS]

Hi Berkay,

Sorry but I fail to understand the scenario you are describing. Can you add some flow/sequence diagrams? Or at least a written order of actions?

BR, Ulysses