Re: Discuss-gnuradio Digest, Vol 206, Issue 5

[Andy Walls]

> Date: Fri, 6 Dec 2019 07:22:11 +0100
> From: "Lukas Haase" 

> Hi,
> 
> I am using GRC 3.7.11 on Ubuntu (WSL). When I use the M&M Clock
> Recovery block GRC crashes randomly with this message:
> 
> 
> clock_recovery_mm_cc: ii > ninput_items[0] (3168 > 3167
> python: /build/gnuradio-BBYmSv/gnuradio-3.7.11/gr-
> digital/lib/clock_recovery_mm_cc_impl.cc:214: virtual int
> gr::digital::clock_recovery_mm_cc_impl::general_work(int,
> gr_vector_int&, gr_vector_const_void_star&, gr_vector_void_star&):
> Assertion `0' failed.
> 
> > > > Done (return code -6)

The M&M clock recovery block obviously has an off-by-one error in its
processing.

The M&M clock recovery block is obsolete.  Use the Symbol Synchronizer
block instead, if you must use the M&M TED.


> Based on the plots, the block seems to be working (I get the proper
> bits).
> 
> My input signal comes in small bursts (asynchronously at random times
> which is why I need M&M).
> First I need to filter the signal and center it on its mean value.
> I use the following block for it:
> 
> https://paste.pics/4573d1f2cf7df0d5e039874c51127dd9
> 
> This shows a screenshot, triggered to one of the bursts:
> 
> https://paste.pics/a48ec4aef5ddeeef74e96255d72288b3
> 
> The original bits can be seen (blue/red) and the filtered, mean-
> centered version that will go into the M&M block (green/black).
> 
> Finally the M&M block looks like this:
> 
> https://paste.pics/db179025b5c6e98c3b20e76d56bcf139
> 
> 
> 
> The output of the block looks as expected ... until GRC crashes.
> 
> 
> Is there anything I am doing wrong?

You may want to read this presentation:
https://www.gnuradio.org/grcon/grcon17/presentations/symbol_clock_recovery_and_improved_symbol_synchronization_blocks/Andy-Walls-Samples-to-Digital-Symbols.pdf


Regards,
Andy


> Thanks,
> Luke
>