Re: Controlling GRC parameters with QT Creater

Hi Philipp,

exactly, use a "meta variable" that it's set on every variable changes.

 Sending the meta variable ( dictionary) with each change could be a problem if there are a large number of parameters to be transferred; in that case it might be useful to 'split' the parameter set into 'changed often' and 'changes sometimes'.

 Actually, one could also use a 'list' and then derive the individual variables via the list index... I used a dictionary because they seems a little more descriptive to me.

 In my application there are about ten of them and I have never encountered any problems: my 'Control Unit' and the 'RF head' are connected via a VPN and physically about 40 km apart.

Attached is a small demonstration flow ;-)

Enjoy!

Viitorio, I3VFJ

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lunedì 27 gennaio 2025 18:58, Philipp Niedermayer <p.niedermayer@gsi.de> ha scritto:

Hi Vittorio,

not sure I get it, according to [1], [2] and [3] linked below it is clear, that the variable name configured as parameter is used, and the actual <name> of the message pair is ignored.

Are you suggesting to to put all my variables in a single "meta variable" of dict type? I.e. something like `meta_var = {"freq": 1e6, "gain": 5}` and then access it like `meta_var["freq"]` instead of just `freq`? That's an interesting approach, but it would require to change all variables in the flowgraph, and to always send all variables even if you only want to change a single one, right?

Best
Philipp

[1] https://wiki.gnuradio.org/index.php/Message_Pair_to_Var
[2] https://github.com/gnuradio/gnuradio/issues/6574
[3] https://github.com/gnuradio/gnuradio/blob/8cbd8526b50a96188119d11bf69b2fc701edb38a/gr-blocks/python/blocks/msg_pair_to_var.py

Am 27.1.25 um 17:33 schrieb vittben@pm.me:

Good evening everybody!

Regarding this:

"...PS: I found that the "Message Pair to Var" block is not very flexible, since it only allows to set one specific variable...."

Actually a variable can also be a dictionary: simply creates a dictionary in which tag/value pairs refer to other variables.

In a mine (never finished) project I'm using this to transfer several settings (TX_freq, RX_freq, various gains, PTT) between a remote RF head (Pluto+ and amplifiers) and a local CONTROL unit, over ZMQ sockets with very good results

I hope it can be helpful...

Vittorio, I3VFJ

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lunedì 27 gennaio 2025 09:16, Philipp Niedermayer <p.niedermayer@gsi.de> ha scritto:

Dear Muhammad,

you can use ZMQ blocks to send messages to your GR program. Either directly to the message port of USRP sink, or use a "Message Pair to Var" block to update a flowgraph variable. You can read more about these blocks here:

• https://wiki.gnuradio.org/index.php/Understanding_ZMQ_Blocks
• https://wiki.gnuradio.org/index.php/Message_Pair_to_Var
  

PS: I found that the "Message Pair to Var" block is not very flexible, since it only allows to set one specific variable. I am currently working on a similar block that allows me to change multiple variables based on the message car, so that I can control my flowgraph by sending (variable_name, value) message pairs. Once I got it to work, and if there is interest, I could open a PR.

Best
Philipp

Am 25.1.25 um 8:08 schrieb Muhammad Anas:

Dear GNU Radio Community,

I'm working on a project to control a USRP channel frequency from QT creater GUI application, is it possible to implement a communication between QT and GRC using xmlrpm or tcp block etc to control the GRC parameters in real-time on the same computer in window.

Kindly help me to achieve this communication.

Regards

Muhammad Anas