A uni project: the movie: the game: the sequel.
The goal of this project is to learn how the Raspberry Pi works in conjunction with Pure Data. We want to control a PD patch with live midi-input and ideally also have the ability to sample incoming audio.
- Raspberry Pi (we used the fourth iteration of the microprocessing unit commonly known as the Raspberry Pi)
- adapter to power your Pi
- micro SD card, at least 8gb
- ethernet cable
- usb to ethernet adapter
- audio interface (we used a Focusrite for the sampling part of the synth, other audio interfaces might cause inconveniences)
- midi controller of some sort
- a device – or more precisely: a transducer – that converts sound into an electrical signal (you might call it a microphone)
- speakers
Download a Raspbian image from the Raspberry Pi site. We recommend Raspbian Buster with desktop. Write your downloaded image to your SD card. On Windows you can use Rufus. To enable SSH you'll need to a make an empty file called ssh (without an extension!) and place it in the root of your SD card. That's it, really.
Now it's time to grab your ethernet cable and usb to ethernet adapter. Connect the ethernet cable to your adapter and Pi. Connect the usb to your already working computer. To allow your Raspberry Pi to connect to the internet, you'll need to share your already working computer's internet connection with your Pi. On Windows you'll need to change your adapter properties like this:
Open up your favorite terminal. You can use PowerShell if you're on Windows (perhaps consider changing the color scheme to make it actually readable). Stretch your fingers, we're going to start typing!
ssh pi@raspberrypi.local
The default password is raspberry. You won't see letters or * appearing when typing your password - don't worry, your keyboard is still working! You'll probably get a prompt yabbering about so-called ECDSA fingerprints. To shut it up, answer with a confident yes. If all went well you'll now be logged into your Pi!
Let's make our stay a more comfy one by configuring some options. It's handy to maximize your terminal window for the coming steps. We're going to run a program requiring special security privileges. That means that we need to prepend our command with the sudo (superuser do) command:
sudo raspi-config
You'll be greeted by a big menu:
You can navigate through the menu with the arrow keys. Select option 5 and enable P3 VNC. You could also consider other options like changing your password and locale, or enabling Wi-Fi. This is not in the scope of this manual though, so let us move on!
First things first, download and install VNC Viewer on your already working computer.
If you were wondering how the last step made our stay more comfy: fret not, you'll find out right now. Escape the big menu and return to the regular terminal environment. To start VNC Viewer, simply type vncserver (on a Pi 4 you might run into some resolution problems, vncserver-virtual -randr=1920x1080 may solve that). Your terminal will spit out a bunch of text, but we only need the last bit:
New desktop is raspberrypi:1 (*IP-address:port*)
Your desktop might have a different name. Make sure to use that one and not the one above. Open up VNC Viewer and let's connect to your Pi.
Login with your username and password. Now you can comfyily navigate your Pi!
Installing Pure Data is easy as Pi:
sudo apt-get install pd
If you want a more up-to-date and extensive version of Pure Data, we can recommend Purr Data (which is also slightly less easy to install).
The included patches are made for use with Purr Data and won't work with vanilla pd.
To configure midi we need to use a program called aconnectgui. You might not have it installed, so just in case:
sudo apt-get install aconnectgui
You can plug-in your midikeyboard now and start Pure Data. Open the preferences window (Ctrl + P) to select your audio interface as I/O and make sure that you're using the ALSA audio api.
Hop over to the MIDI tab, set the midi api to the ALSA one and both ports to channel 1.
To make use of these channels we need to run aconnectgui to connect them to your midikeyboard. You can do this by clicking on the cable-icon and drawing the right lines between the corresponding channels.
Almost there! Download this repository using git:
git clone https://github.com/nooisy/pi-pd-synth.git
Open the main.pd patch and start having fun!
Raspberry updated the HDMI display graphics connection stuff for the Pi 4 (vc4-fkms-v3d) which resulted in cool stuff (4k @ 60hz), but it also made using different resolutions on a headless Pi a bit of a hassle. Forums talk about editing boot options which, sadly, didn't do much for us. The xrandr utility that usually takes care of the outputs for a screen also behaved in a different-than-normal way (missing modes, not accepting new modes). In the end, specifying the size of the VNC virtual desktop like this vncserver-virtual -randr=1920x1080 made it work.
Coming from Max/MSP, Pure Data took getting used to. Lots of objects behave just a bit differently. Especially the way buffers work. No suchs objects like [buffer~] or [groove~] in PD. To write to main memory in PD you have to use array objects. Johannes Kreidler's PD book/site really helped with understanding that process. Trying to manipulate the arrays gave us more on insight on the workings of samples, sample rates, phase, phasors, Hanning windows, delay lines, etc.
PD's helpfiles are lackluster in comparison to the Max ones. The excellent community on the PD Patch Repo Forums luckily has great explanations and often share their patches with illustrative examples.
https://www.raspberrypi.org/forums/
https://puredata.info/docs/manuals/pdrefcards/pd-refcard-en.pdf
http://www.pd-tutorial.com/english/index.html
http://write.flossmanuals.net/pure-data/introduction2/
https://www.youtube.com/playlist?list=PL12DC9A161D8DC5DC
https://www.youtube.com/playlist?list=PLqJgTfn3kSMW3AAAl2liJRKd-7DhZwLlq
https://www.youtube.com/playlist?list=PL0dqIhYnzlnPeQAC5mRzKq5HLwfBGRYaO
https://forum.pdpatchrepo.info/
https://patchstorage.com/