Re: [Discuss-gnuradio] Bug with scrambler in hierarchical block

[Daniel Estévez]

El 14/02/17 a las 19:15, Bastian Bloessl escribió:

> I tested the flow graph with current next and master branches and didn't
> see the problem, i.e., the first byte of both message debug blocks was
> always 0xff.
> 
> Are you sure you don't use any custom patches?

I only have the Viterbi decoder patched.

This problem also happens to other people. I found the bug originally in
my AO-73 decoder in gr-satellites:

https://github.com/daniestevez/gr-satellites

The CCSDS descramble will descramble incorrectly the 1st bit in the
packet (except for the first packet) and you'll always end up with 1
error in the Reed-Solomon decoder. Other users have also told me about
this problem.

Testing this is more elaborate than with the simple flowgraph I sent
before. In case anyone wants to try, the sample recordings at

https://funcube.org.uk/working-documents/telemetry-examples/
http://www.sigidwiki.com/wiki/FUNcube-1_Telemetry

can be used together with the audio streamer in gr-frontends.

Regarding the simple flowgraph I sent before, I think this problem is
not so easy to reproduce. It probably depends on what version you're
running and all sorts of things. I changed the name of the "packet_len"
tags in the CCSDS scrambler and the problem disappeared in my simple
flowgraph but not in the AO-73 decoder from gr-satellites.

I'm afraid I can't be of much more help right now. If I notice anything
new I'll write again.

Regards,

Dani.

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