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

From: Daniel Estévez
Subject: Re: [Discuss-gnuradio] Bug with scrambler in hierarchical block
Date: Tue, 14 Feb 2017 16:16:10 +0100
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El 14/02/17 a las 15:46, Daniel Estévez escribió:
> Hi,
> I have a hierarchical block that implements a CCSDS synchronous
> (additive) scrambler/descrambler.
> I have noted that the scrambler doesn't reset properly. The first bit is
> wrong all the times except the first one. However, if I take all the
> block inside my hierarchical block and put them on a flowgraph,
> everything works fine. I'm puzzled.
> See the attached files. The hierarchical block is ccsds_descrambler.grc.
> The test flowgraph is test.grc. It contains both the "CCSDS descrambler"
> block and a set of blocks which is precisely what is inside the "CCSDS
> descrambler" block. By default, you see the output of the CCSDS
> descrambler. Note that the first time the first byte is 0xff but the
> remaining times it is 0x7f. However, if you disable one of the message
> debug blocks and enable the other one, you'll see that the first byte is
> always 0xff.
> I have no clue about what could be the problem.
> I'm running GNU Radio

I've been doing some further tests and it seems that it doesn't have to
do much with whether the descrambler is implemented as a hierarchical
block or not.

In some other flowgraphs I have I've replaced the descrambler
hierarchical block by its "contents" and the problem with the first bit
being wrong after a reset persists.

Perhaps something about the scheduler?



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