Driver for ST25R3912 with external microcontroller.

[ADoan.1]

Hi ST support team,

We use ST25R3912 with solution for design phone (use chip microcontrller SM6150(Qualcomm)),

We have problem need you support list in below:

1:  If we design without MCU_CLK signal, do we can use Transparent mode for AFE and framing implemented in the external microcontroller?

2: Can you support about the driver can implement all your NFC requirements (NFC card emulation, NFC reader/writer, NFC peer-to-peer) if you use SPI bus only (internal framing in NFC chip).

Thanks,

AnhDN

[Ulysses HERNIOSUS · Accepted solution]

Hi AnhDN,

ad 1)

Transparent mode usage typically requires modulation of the field synchronous to the carrier. Running from a different clock may be feasible for short frames but at always existing frequency deviations they will at some point move out of sync to a point where communication breaks.

Thus I consider usage of MCU_CLK for transparent mode essential.

ad 2)

ST25R3912 can act as NFC Forum reader/writer. If you look at https://nfc-forum.org/our-work/compliance/certification-program/certification-register/ you will find ST25R3911B under "Reader Devices". For this certification only the internal framing of the ST25R3911B was used.

ST25R3912 is essentially the same device. However ST25R3911B and its derivates (ST25R3912 up to ST25R3915) don't support load modulation - even when using transparent mode. So they don't support card emulation and passive P2P target. So they cannot be certified as Universal Devices.

Theoretically you could add external circuitry to do the the load modulation external from an MCU. But we cannot share any experience for such an approach.

Regards, Ulysses