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De-whitening, endianess and length issues

ltoso.1
Associate II

I am trying to use the WL55 with a legacy 2-gfsk system that relies on CC1120 chip.

The major issue here is related to de-whitening of the received data.

I am editing the subghz ping pong example.

Band, AWG and datarate are coherent with the legacy system, but the data I receive is waaaaay too long compared to the expected (and transmitted) one.

First issue: I'd like to receive all the data over the air, preamble and sync word included. I am not sure I am receiving it because the data does not look like the sync word (that is 0xAA in the CC1120 and 0x55 on the WL55). I am relying on the variable-length packet format BTW.

Second issue: in Variable length packet format the whitening is applied both in tx and rx ALSO to the legth byte hence the data I receive is arbitrarly long.

Third issue: the PN9 algorythm in CC1120 and in WL55 are different, something related to IBM vs CCITT, hence the only solution I can figure is to receive whitened packets and de-white them in software. I don't think changing the initial seed for the algo could help me in any way.

Any hint on these 3 points?

K.R.

L.

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