2019-01-31 12:46 AM
Hello all.
I use ST25R3911B-DISCO and dynamic tag ST25dv04k
When reading data from FIFO come bytes with a redundant cipher.
Suppose the code is presented as custom manchester code:
After that, you need to perform a cyclic shift to the right by 3.
It all works with the exception of some bytes.
For example: in fact (in tag buffer) - 0xAA. Recived 0x3333, after decryption - 0xAA. All ok
But it happens: in fact - 0xCC. Recived 0xb3b4, after decryption - 0xCA.
Where can I read more about this cipher?
Or what am I doing wrong?
Solved! Go to Solution.
2019-01-31 04:49 AM
Hi,
actually this is not a cipher but the bit coding VICC->VCD. It is Manchester coding and e.g. defined in ISO/IEC15693-3 or NFC Forum Digital specs.
ST25R3911B does not perform ISO15693 bit coding/decoding internally.
If you experience issues, then you should start off by looking at the SOF pattern and see why you experience a shift here. Possibly the timings (MRT of 3911B is not set appropriately).
Does the same happen using the ST25R3911B-DISCO GUI/firmware? Which version? If so then please give details how to reproduce this. Otherwise the firmware sources are available and are working.
Regards, Ulysses
2019-01-31 04:49 AM
Hi,
actually this is not a cipher but the bit coding VICC->VCD. It is Manchester coding and e.g. defined in ISO/IEC15693-3 or NFC Forum Digital specs.
ST25R3911B does not perform ISO15693 bit coding/decoding internally.
If you experience issues, then you should start off by looking at the SOF pattern and see why you experience a shift here. Possibly the timings (MRT of 3911B is not set appropriately).
Does the same happen using the ST25R3911B-DISCO GUI/firmware? Which version? If so then please give details how to reproduce this. Otherwise the firmware sources are available and are working.
Regards, Ulysses