[USRP-users] Passing arguments to an RFNOC block

Paul Boven p.boven at xs4all.nl
Fri Mar 1 04:54:32 EST 2019


Hi again,

After way too much time spent trying to debug my issues, and renaming 
all the variables, I wasn't getting anywhere. Then I discovered xmllint 
which pointed out a few (!) more xml errors in a completely different 
section of the rfnocblock XML file. After fixing this, I've got the 
resampler part working.

Regards, Paul Boven.

On 28/02/2019 10:30, Paul Boven via USRP-users wrote:
> Hi Jonathon,
> 
> Thanks for looking at the block, and spotting the mistake.
> Unfortunately that doesn't stop the swig part from failing, so I'll keep 
> digging further.
> 
> Regards, Paul Boven.
> 
> On 28/02/2019 04:19, Jonathon Pendlum wrote:
>> Hi Paul,
>>
>> Your Nocscript has an error on line 47, you are a missing a comma: 
>> LE($config 1) should be LE($config, 1). That may not be the source of 
>> your issue, but try fixing that first.
>>
>> Jonathon
>>
>> On Thu, Feb 28, 2019 at 1:14 AM Paul Boven via USRP-users 
>> <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>> wrote:
>>
>>     Hi everyone,
>>
>>     As part of the VLBI[1] backend that I'm making in RFNOC, my first 
>> step
>>     is to make a rational resampler. It takes the 100MS/s signal from a
>>     TwinRX, and reduces it to 80MS/s. This can be done with a 5:4
>>     resampler.
>>     In order to make this work, I'm using the axi_rate_change block.
>>
>>     Although the block works in simulation, I keep running into problems
>>     with the GRC integration, in particular SWIG throwing run-time 
>> errors.
>>
>>     The problem seems to be in the way that the arguments (N, M, config)
>>     are
>>     passed around, but studying other blocks like the DDC block hasn't
>>     provided the clues for me to get past this hurdle.
>>
>>     The resampler itself does work, which I tested by having it emit 
>> zeroes
>>     instead of the 'deleted' samples, and using a 'keen 1 in N' in GRC
>>     itself.
>>
>>     At the moment, the block exits in VLBI_swig.py in set_arg:
>>     return _VLBI_swig_resamplerd5x4_sptr_set_arg(self, *args)
>>     RuntimeError: SyntaxError: Parsing Stopped at: $N, 5)
>>
>>     If you're familiar with RFNOC, can you please have a look at:
>>
>>     http://www.jive.nl/~boven/rfnoc-VLBI
>>
>>     It contains the source, and also a compiled bitfile for the X310 for
>>     your convenience (but use at your own risk, of course).
>>
>>     Regards, Paul Boven.
>>
>>     [1] Very Long Baseline Interferometry
>>
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> 
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