Re: [Discuss-gnuradio] Matplotlib and GNU Radio: Dynamic plot

[Marcus Müller]

Interesting!

So, my approach in this case would be:

1. Write a block that takes the data from your flow graph, and converts it to a format (e.g. JSON, KML, GPX,…) that makes sense for the receiving end. This data should be emitted as messages (not python variables).
2. use a UDP or ZeroMQ (I recommend the latter) to send these messages out
3. Write a really minimal web application that receives the things from 2. and updates a browser visualization. Use your own images or simply OpenStreetMap as base layer.

You can of course also write your own visualization block. That's absolutely feasible; it's just that matplotlib is really not the tool of choice for that here. But it's definitely not the software you need, either, to draw points on an image. There's literally dozens of python toolkits that can display images and modify them.

Writing visualization blocks will require you to think about how to thread them. And since it'll be hard for the block to interact with the main thread, but that would be necessary for GUI blocks to work, I don't know whether that is an entry level project. Anyway, do have a look at Tim O'Shea gr-pyqt ; it contains python visualization blocks, and I don't think it'll be hard to understand and modify them. Look at the raster_plot.py for example.

Best regards,

Marcus

On 09/20/2017 10:21 PM, Ali wrote:

Hi,

Actually I want to draw coordinates on a map. So I want to upload a map(a png file, like using imshow function in MATLAB, matplotlib) and then draw points on this map. I think it is not possible by just using QT instruments. 

Regards,

Ali

2017-09-20 21:14 GMT+03:00 Marcus Müller <address@hidden>:

Dear Ali,

don't convert data streams to Python variables. Just use the Qt instrumentation plots that directly come with GNU Radio, they are actually meant for this.

Matplotlib is *definitely* not what you want to use for live plots. Far too slow.

Best regards,

Marcus

On 09/20/2017 01:29 AM, Ali wrote:

Hi everyone,

I have a flowchart in which USRP's are running and after some blocks 2 variables are produced at the output.

As the inputs change, outputs change. I want to dynamically plot these two variables on x and y axis. I am willing to use matplotlib.

What do you suggest to plot these variables?

1- Write them to a .txt file and read by matplotlib at the same time,

2- Without writing the variable anywhere, directly use in matplotlib(somehow)

3- Write a python block and use in GRC directly

I don't know whether these can be applied or not. I am open to any ideas.

Regards,

Ali

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