NFC Tap App (Android) FTM - Write MSG CRC Calculatin Method

[jerry chang]

Hi Experts

I used NFC Tap App to transmit data(use FTM write message cmd), transmit 10 byte

As my analysis below the last 4 byte should be the CRC(4 byte)，I think it's use CRC32 method, but I can't calculate the result as same as the App

Results by using on-line CRC calculator

Could you please verify this for me? thank you very much!

[JL. Lebon]

Hello Jerry,

I think you are mixing the Write message command (ISO15693 frame) with something else.

The Write Msg command format is:

02 aa 02 | 0f | 05 00 01 02 03 04 05 06 07 08

cmd code | msg len | data

Control Byte and Packet length and CRC32 you are inserting in the middle of the Write Msg command do not belong to this command.

Best regards.

[Tesla DeLorean]

Hi, can you provide a cite to the document with the CRC and example packet code, and perhaps the ISO standard that's coming from.

Thanks,

[JL. Lebon]

Hi Jerry,

Any news from your side on this issue ?

Best regards.

[jerry chang]

Hi, Sorry for lately respond because I just ignore the CRC and proceed to develop my application.

The protocol I described is "FTM protocol" which you can refer to below url:

https://www.st.com/resource/en/user_manual/um2062-firmware-for-the-st25dvdiscovery-boards-stmicroelectronics.pdf

And I just wanna find which CRC32 method was adapted in ST FTM protocol

Thank you!

[Olivier L · Accepted solution]

Hi,

The ST25SDK contains a class for this CRC verification. You can use it with:

import com.st.st25sdk.Crc;
 
byte[] computedCrc = Crc.computeCrc(data);

Best regards

Olivier