Re: [Discuss-gnuradio] Updating variable by passing message

[Marcus Müller]

Hi Mohammad,

this sounds like a wise architecture, using a message to update settings.

To answer your question:

> how i can update a variable block value in python code , is that
possible at all ?

As you noticed, yes, that's possible, because the GUI sliders etc. do that!
However, it only works because these are actually living directly in the
top_block python code.

What you **can** do is write a python block, which, as a parameter,
takes a reference to the top_block (or hier block) which it "lives" in,
and stores it in a class member.

Then you can call .set_variablename(value) on that in your message handler.

I do **not** recommend that, however. It breaks the inherent thread
safety of message passing, makes a large detour through python that will
cost a lot of copies and unnecessary type conversions "under the hood"...


Instead, better simply go and improve the FFT Filter! Add a message port
that accepts new taps! I think we'd all love to see that becoming a
feature, so if you can, please make that change and contribute it to GNU
Radio! Also, it's less work than writing the python block that I
mentioned above.

Best regards,
Marcus


On 12.08.2017 11:51, mohammad nejati wrote:
> Hi ,
> I want to update taps in "FFT FILTER" block in run time , i have a
> block that can send this taps as a message every 1 secound . i write
> an python block witch get this message what i want to do is get this
> message and update value of a variable block wich is used in FFT
> FILTER . but i dont know how i can update a variable block value in
> python code , is that possible at all ?
>
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> Discuss-gnuradio mailing list
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Re: [Discuss-gnuradio] Updating variable by passing message

[mohammad nejati]

Thanks Brian ,
But how work QT Range slider ? for example if use a range slider for
one of taps value in FFT taps for example
[0.1,0.001,0.2,My_range_slider_ID,0.2,...] changing value of slider in
run time update FFT filter taps without any problem . i need some
thins like that but it get value from message port .

On Sat, Aug 12, 2017 at 2:34 PM, Brian  wrote:
> Mohammed,
>
> That's good question and I'm working on a project that requires me to do
> similar but mine is frequency.
>
> I believe that once a code is run and your receiver is running that changing
> a variable is not possible.
>
> However I have a workaround, I am using a file as a source which will be
> either blank (so no action takes place) or a frequency value, this triggers
> a reset of python and then reads in the value as a variable.
>
> This works quite well in my case but may not suit all applications.  My
> receiver only needs to be on when I trigger it from the transmitter, it
> can't be used if you're looking for a constant FFT plot.
>
> Hope this helps and if there are any suggestions for a more refined solution
> that would be great.
>
> Brian
> 
> From: mohammad nejati
> Sent: ‎12/‎08/‎2017 10:51
> To: discuss-gnuradio@gnu.org
> Subject: [Discuss-gnuradio] Updating variable by passing message
>
> Hi ,
> I want to update taps in "FFT FILTER" block in run time , i have a
> block that can send this taps as a message every 1 secound . i write
> an python block witch get this message what i want to do is get this
> message and update value of a variable block wich is used in FFT
> FILTER . but i dont know how i can update a variable block value in
> python code , is that possible at all ?
>
> ___
> Discuss-gnuradio mailing list
> Discuss-gnuradio@gnu.org
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

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Re: [Discuss-gnuradio] Updating variable by passing message

[Brian]

Mohammed,

That's good question and I'm working on a project that requires me to do 
similar but mine is frequency.

I believe that once a code is run and your receiver is running that changing a 
variable is not possible.

However I have a workaround, I am using a file as a source which will be either 
blank (so no action takes place) or a frequency value, this triggers a reset of 
python and then reads in the value as a variable.

This works quite well in my case but may not suit all applications.  My 
receiver only needs to be on when I trigger it from the transmitter, it can't 
be used if you're looking for a constant FFT plot.

Hope this helps and if there are any suggestions for a more refined solution 
that would be great.

Brian

-Original Message-
From: "mohammad nejati" 
Sent: ‎12/‎08/‎2017 10:51
To: "discuss-gnuradio@gnu.org" 
Subject: [Discuss-gnuradio] Updating variable by passing message

Hi ,
I want to update taps in "FFT FILTER" block in run time , i have a
block that can send this taps as a message every 1 secound . i write
an python block witch get this message what i want to do is get this
message and update value of a variable block wich is used in FFT
FILTER . but i dont know how i can update a variable block value in
python code , is that possible at all ?

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