Hello everyone,
I've been working lately with puredata and python together using python as the brain of the system and puredata as the audio engine. For the moment I've been successfully sending messages from python to puredata thanks to this tutorial:
Make Python and Pure Data communicate on the Raspberry Pi

Now I want to reverse the process sending float values from puredata's vumeters to python and then represent them in led vumeters that are connected to the raspberry gpios.

One question is, how do I package the different vumeters values to connect them separately to the netsend object in pd? (Like the following screenshot)

I made a python script with the pdreceive command but I don't know how to take the message from the string concatenation:

I need to take each vumeter value separately from puredata and be able to identificate them in python.

Does anyone knows how to solve this problem?

Thank you!

@JackPD Hi, you could try something like this, which sends a 2-element list with the first element being the vu-meter ID, and the second being the vu-meter value.

I don't know about python but maybe you're able to sort the incoming messages by their first value in the same way as [route] would in Pd.

Thank you weightless, sounds like a good idea. With this method, will the 3 variables be sent as one big string? If I have the first pvu 10, the second 6 and the third 20 for example, how netsend will send this? Something like 1 10 2 6 3 20?

@JackPD That is right, each vu-meter will send a 2-element string (called a list in Pd) exactly like you wrote. You can also use the [netreceive] object to check what is being sent.

EDIT: I wasn't clear: they won't be sent as a 6 element string, but whenever there is a change in one of the vu-meters, it will send out the respective id number and the value.

In case that the three elements are sending values at the same time, will the three be sent separately at different times? I'm reading about the pack and route function in puredata, but your solution it's pretty simple and looks efective, I'm gonna create a netreceive to see what it receives from the netsend.

I've made a receive object and seems that the messages are shown in the order that I've made the three send objects (1 3 2), and the most important, each one in separate messages. That's very interesting.

@JackPD Yes, since the three pvu~ objects output their values at the same time, the order of creation of the send objects will determine which one is output first, although there is no real delay between them.

If you have a way in python to parse the incoming messages according to the first element (like route does), then this should work. Otherwise, you can use [pack] to send a 6-element list to [netsend], and then break it down in python.

@weightless Yes, in python is easy to split strings by counting whitespaces:

>>>data = “'1 1.19'”
>>>split = data.split(“ “)
>>>split

[‘1’, 1.19’]

And it will work to with the pack too:

>>>data = “'1 1.19 2 5.6 3 7.3'”
>>>split = data.split(“ “)
>>>split

[‘1’, ’1.19’, ’2’, 5.6’, ’3’, ’7.3’]

The second way I think is better because I have the data always in the same position and I can make a function that take the data from the same position everytime and assign each of them to different variables.

Maybe this is not the best way of communication, but I think it is pretty solid for its simplicity.

And again, thanks man for helping me out, this was driving me crazy.

@JackPD You're welcome, glad to help out.
If you're packing the six values in one message, make sure to send a bang to pack after you update the "cold" inlets of pack.

@JackPD Hello. and apologize if i'm writing in a very old thread but i'm trying to do something very similar and i stumpled across this post. i wanted to ask you how did you menage to represent the vu values in Led meter?
how can Phyton process these data and use them straight away for controlling the GPIOs?
thanks in advance for any hint! cheers

@nhouse [comport] is the Pd object that you could use to talk directly to the GPIO pins...... especially if you want high speed data.
If you just want to set pins in/out and high/low I think [wiringpi] will do that.
You can search for them from the Pd top menu with... Help.. Find externals.

[pvu~] values in Pd are from -99 to +12 with 0 @ 0db.
It samples the incoming audio at a rate you can set and outputs values in that range.
It might also be available through Find Externals...... and it was built into Pd extended.

I don't know how to program Python but I know that pdreceive (an executable that should be somewhere in your Pd folders...... probably the /bin folder) can be used to receive data from Pd [netsend] by calling it in Python....... as in the first post.....
David.

@whale-av hello!
i will need to drive a series of led WS2812B given an audio level on a puredata . so essentially i need to mimic the pvu~ with the leds as well as JackPD wanted to do (i believe).
The comport object seems like a good solution since it doesn't require the communication with phyton but it sounds a bit tricky to make it work.

@nhouse It looks like you will need to use the PWM or PCM or I2S pins for that....... and not the UART so not comport.
You might loose the audio out from the PI.
Some reading.....
https://github.com/jgarff/rpi_ws281x
https://www.raspberrypi.org/forums/viewtopic.php?t=201516
And with some python (and electrickery) here.....
https://tutorials-raspberrypi.com/connect-control-raspberry-pi-ws2812-rgb-led-strips/
Once you have the python code doing what you want with the leds (for say X = 0-112..... but it can be scaled or shifted in Pd before sending) you can use pdreceive to receive the data from pd.
That will be the easy bit.
David.

I am trying to get Pd on a raspberry 3 to interact with GPIO. I need to blink some LEDs and to receive data from accelerometer. I have the pdsend to netreceive up and runing, but I can not seem to manage to receive, store and display the data from Pd - netsend in Python using pdreceive. How did you end up writing the code ?

@zangpa Python needs to find pdreceive when it is called from your code so you probably need to copy it into Python somewhere.
Sorry..... I am not a Linux person..... but maybe into the folder that contains the Python binaries.

I lifted this from a website a while ago...... Guitar Extended.pdf
It shows how to send from Python to Pd and I imagine the code will be similar but opposite for sending back....... knowing as little about Python as I do about Linux.

At the end..... in French..... the author suggests using OSC instead if pdreceive is problematic...... using a Python OSC module.
David.

Hi,
You can find here a python coded client/server running in a PyQt5 application.
As it's designed as FreeCAD plugin, it needs modifications to run standalone but I can help if needed.