I am using NFC424 P2P communication.
We are using our own CRC routines for our application, as we recognized problems with TRF's internal CRC calculation in noisy environments.
Thus we want to disable the internal CRC calculation of TRF7970A. This should be achievable by using direct command 0x10 (Transmission Without CRC ) instead of 0x11(Transmission With CRC). But this does not seem to work, as the NFC frame has the same length in both cases (commands 0x10 and 0x11). But it should be 2 bytes shorter in this case!
For test purposes I sent 1 byte payload (0xAA). Including our CRC calculation and the size byte this results to 4 bytes written into FIFO. On the Air interface I expect to have a total size of ~ 56 Bits Preamble, 2 Sync Bytes(0xB2,0x4D), 1 Size Byte (0x04), 1 Data Byte (0xAA), 2 CRC Bytes (00x12,0x17). But there are additional 16 bits appended by the TRF, also when sending with direct command 0x10 (Transmission Without CRC ).
Am I missing something? How do I get rid of the TRFs internal CRC?
Regards Marco