Override custom commands

BryanAamot · ‎2024-09-04

The ST25DV and M24LR define custom commands for specific purposes. Is there a way to override these command values so I can send a small few byte payload over NFC to the chip, read the payload, and send back a response with the same command value?

The custom command range starts at A0 so I'll use that as an example. Since the ST25DV and M24LR define A0h for Read Configuration, does that mean I can't use A0 for something else?

Brian TIDAL · ‎2024-09-05

Hi,

If I understand your use case, you would like to send a payload over NFC to the tag and then read this payload through the I2C interface.

The ST25DV features a 256 bytes mailbox. Can this mailbox fit with your needs?

Note: the M24LR is in NRND state (Not Recommended for New Design).

Rgds

BT

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BryanAamot · ‎2024-09-05

Hi Brian,

Thanks you for the reply! Yes, I want to send a payload over NFC and read it through I2C. The restriction I have is that I need to use specific custom commands for this. This is for an existing application so I can't change the software on the iPhone. I don't want to specify which commands on an open forum so I'm using the example. So, let's assume I want to use A0, A1, A2, A3 for the custom commands.

Best,

Bryan

JL. Lebon · ‎2024-09-05

Hello,

I can send whatever custom command you want from iOS, but the ST25DV and the M24LR only understand the custom commands that are defined in the datasheet, with the format that is defined in the datasheet. Any other custom command will be answered with an error.

Best regards.

BryanAamot · ‎2024-09-05

Thank you both for the rapid responses!

If I understand correctly, the ST25DV chip does not allow the embedded software to extend the NFC custom commands for its own purpose. Instead, it must stick with the protocol as defined in the spec sheet.

Does the ST24DV chip does not offer a command/response feature where I can send arbitrary data from a smart phone and receive a response?

Thanks again!

JL. Lebon · ‎2024-09-06

Hello,

" the ST25DV chip does not allow the embedded software to extend the NFC custom commands for its own purpose. Instead, it must stick with the protocol as defined in the spec sheet"
-> yes, exactly. The ST25DV does not embed any software and can't be extended in such a way.

What do you mean by "send arbitrary data"? If you mean commands that are unknown by the ST25DV, the response will be an error.

Best regards.