ST25DV16 - CRC16 Calculation for when the Error flag is set

[Gustavo.Laureano]

Hi,

I am receiving the wrong CRC16 value from the tag when it is answering error flags, for example:

2020-12-16 14:01:18.143 writeMsg >> 02AA0200AA

2020-12-16 14:01:18.148 writeMsg << 0F0F68EE

I forced an error there (writing to the MB when it is off) and the tag correctly answered 0F0F, but the answered CRC (68EE) is not correct, according to the standard it should be 0x7478

What am I doing wrong here? Is the tag really answering wrong CRCs for error codes or is there any other reason why this value is different?

Thanks,

Gustavo

[Brian TIDAL]

Hi,

The 0F0F68EE answer sounds strange. On my side the answer is 010F68EE (in that case the CRC 68EE is correct). is it a kind of trace error/printf error in your log?

Rgds

BT

[Gustavo.Laureano]

Hi Brian,

That's strange

I tested it both with ST25PC-NFC tool on my computer and an application that I developed myself... on both cases using a FEIG ID CPR30, and on both cases all tags (16K and 64K), returned 0F0F68EE

But now I decided to test with my cellphone, sent the raw NFC command and the answer was indeed 010F

Now it seems to be some bug on the FEIG driver or hw... but it give wrong results only on this specific case.. any other suggestions?

Thanks for your help

BR

Gustavo

[Brian TIDAL]

Hi Gustavo,

the tag can only send 00 or 01 as response flag, so I tend to believe the issue is on reader side. If you have a NFC spy, you can check the real value being returned by the tag or you can use a scope with a simple loop (but in that case you would have to decode manually the tag response...). You can also contact FEIG so that they can investigate on their side.

Rgds

Bruno

[Gustavo.Laureano]

Thanks Brian

It seems to be really a problem with the FEIG reader / driver, as I get the correct 010F response when I transceive with a smartphone.