The envisioned application is event driven: send a control word from a client,
wait for the even to complete (e.g. move antenna to target position), start
streaming data for a given amount of time, and when enough data is collected 
to new position. Of course timing cannot be relied on with a non-real time 
operating system whose load is not predictable.

I did use successfully Python Module to implement the server and tune the UHD 
during the week end without editing the Python code (why the Python Module must 
be entered
through the GRC Python editor and not externally for the updates not to be lost 
is still
not yet understood). Will have a look at this new Python Snippet feature.

Thanks, JM

JM Friedt, FEMTO-ST Time & Frequency/SENSeOR, 26 rue de l'Epitaphe,
25000 Besancon, France

June 22, 2020 2:05 PM, "Albin Stigö" <> wrote:

> It might be difficult to control GPIO with precise timing on raspberry pi 
> depending on what you
> want to do... A few hundred khz might be ok though. libgpiod is the new 
> better Linux GPIO API.
> --Albin
> On Mon, Jun 22, 2020, 13:25 Marcus Müller <> wrote:
>> It gets even better:
>> We've launched a feature in (and on master before that, as we do
>> with any feature that ends up in a maintenance release) that we hope
>> doesn't come back to bite us due to enabling unclean design. But, we
>> must build best practices so that it doesn't go unused, either, so:
>> Assuming you're using GNU Radio (or later, once we release
>> something), you can make use of the "Python Snippets" in GRC.
>> Cheers,
>> Marcus
>> On 18/06/2020 23.17, Marcus D. Leech wrote:
>>> On 06/18/2020 03:54 PM, wrote:
>>>> My approach:
>>>> * build your grc chart from GNU Radio Companion and generate the .py file
>>>> * edit the py file and import pygpio
>>>> * play with the RPi4 GPIO in your python script.
>>>> See attached script, with a python server included in the Python script
>>>> to control an RF switch from a GNU Octave TCP/IP client talking to the
>>>> Python
>>>> TCP/IP server.
>>>> I am presenting this approach to hardware control at
>>>> JM
>>> If you use "Python Module" block, you can write a lot of
>>> non-GnuRadio-esque python, import anything you want, etc, etc. No editing
>>> of the output python required, necessarily.
>>>> --
>>>> JM Friedt, FEMTO-ST Time & Frequency/SENSeOR, 26 rue de l'Epitaphe,
>>>> 25000 Besancon, France
>>>> June 18, 2020 9:40 PM, "Da Fy" <> wrote:
>>>>> Hi All, does anyone have an example of how to control GOIO lines on
>>>>> the RPi4 from within a GRC
>>>>> flowgraph. I’m guessing it’s an OOT module.
>>>>> I need to generate a signal of a few 100Hz & control GPIO lines at
>>>>> various points though the cycle.
>>>>> Alternatively, I could generate the signal & lines with external
>>>>> hardware & read them with
>>>>> GnuRadio.
>>>>> Tnx, Dave

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