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RasberryPi & Pisound minimal build.md

These are instructions for building a stand alone, headless, music computer based on the Pisound audio card and a RaspberryPi 3.

I use this set up in my live performance rig where it does all of the following without breaking a sweat:

  • Audio effects
    • stutter gate (beat sync'd)
    • full sweep LPF & HPF filters
    • multiple delay lines (beat sync'd)
    • reverb
    • 3 band parametric EQ
    • volume controls
  • MIDI processing
    • CC controls for all audio effect parameters
    • MIDI clock master w/tempo controls and display on controller
    • routing CCs from control surface to ext. synths
    • routing keyboard input to different ext. synths
    • set and song timers

The aims of the set up are:

  • Standard Linux distribution for a Pi (Raspian)
  • Minimal installation (based on Raspian Lite)
  • Runs headless at gigs, with minimal system overhead
  • Ability to use X & VNC when connected via a network
  • Support for Puredata and SuperCollider.
  • Low audio latency without excessive fiddly tuning.
    • With all of the above active, I get ~5ms input to output delay!

Assumptions

  • You know what a terminal is
  • You have some passing experience with Linux
  • You have a Mac
    • You could use Windows or Linux, but I don't have detailed instructions for some bits. Most of the instructions are exactly the same.
  • You are brave

Get the Hardware

Pisound from Blokas

RaspberryPi

SD Card

  • Install takes just under 2GB, so go 8GB or more.

Misc

  • SD Card reader if your computer doesn't have an SD Slot
  • Free Ethernet port - either on an Ethernet switch, or on your computer.
    • If on your computer, you must be able to get onto the Internet while that jack is in use by the Pi - so either via WiFi, or your computer has two Ethernet jacks.
    • A USB Ethernet adpater is often just the ticket.
  • Ethernet cable

Set up the Image

1. Download Raspian "lite" image

Download from here: https://www.raspberrypi.org/downloads/raspbian/

You want the version named "RASPBIAN STRETCH LITE"

You can use the "DESKTOP" image, and it will have tons of software already installed and set up.... but its not small by any means. Most of it has nothing to do with running the Pi as a music computer. Further, some of it might well slow the unit down.

2. Burn the image to the sdcard

Note: There are several methods listed on Raspberry Pi site for installing the image onto the SD Card. You can use any of them... but most involve downloading and installing a program on your personal computer. But on a Linux or OS X machine you already have all the tools on the command line. And since you need to be familiar with the command line anyway... I just do it this way.

These instructions are for OS X -- For other systems, see the Raspberry Pi site

Before you insert your SD Card... (If you already did, eject it in the Finder, then physically remove it.)

Open terminal run:

diskutil list | grep ^/dev

You'll see something like:

/dev/disk0 (internal, physical):
/dev/disk1 (synthesized):

These are the disk volumes on your computer. You may have more or just one.

Now, insert your SD Card into a SD Card reader, and into your computer. If your computer asks you about formatting it, just choose "Ignore".

Run the same command again:

diskutil list | grep ^/dev

You should see one more line:

/dev/disk0 (internal, physical):
/dev/disk1 (synthesized):
/dev/disk2 (internal, physical):

Note which is the new one. In this case /dev/disk2 is the new disk, and represents the SD Card. It's disk number is 2. The disk number for your SD Card may be different.

In the commands that follow, when you see disk# replace the # with your disk number.

Now run the following:

diskutil unmountDisk /dev/disk#
cd ~/Downloads
unzip ~/Downloads/2018-04-18-raspbian-stretch-lite.zip
sudo dd bs=1m if=2018-04-18-raspbian-stretch-lite.img of=/dev/rdisk# conv=sync
rm ~/Downloads/2018-04-18-raspbian-stretch-lite.img

Your download file might be named differently. Also take careful note that on the second line there is a sneaky r in front of disk#.

This will take a bit of time. If you are worried, type CTRL-T and dd will print some cryptic indication of it's progress.

When it is done, OS X will automatically mount the newly imaged disk.

Do not eject the SD Card yet...

Enable SSH in the Image

This is very important so that you can connect into the Pi when it boots headless.

After the burning, the disk will be mounted at /Volumes/boot. Run this:

touch /Volumes/boot/ssh

Now eject the SD Card, either in the Finder, or from your terminal, like so:

diskutil eject /dev/disk#

First Boot

The aim at this stage is to get the Pi up and booted, on the network, and to be sure you have connectivity to it.

Network Preparation

If your computer uses wired ethernet, and you have a spare Ethernet jack on your hub or switch or router, you can just plug the Pi into that.

If not, you can connect the Ehternet port on the Pi to the Ethernet port on your computer (or perhaps a USB Ethernet adpater on your computer), sharing access to the internet you get via WiFi. To do this:

  • Ensure you have Internet connectivity
  • Connect your USB Ethernet adapter if you need to
  • Apple menu > System Preferences > Sharing icon
  • Select Internet Sharing (it won't check, that's okay)
  • "Share your computer from" should be showing your Internet connection
  • "To computer using": check the Ehternet port you'll use to connect to the Pi
  • Now check the box next to Internet Sharing
  • Click Start in the dialog that appears.

Set up the Pi

  • Unpack the Pi: Don't put it in any case yet. Don't power it on. Don't attach heat sinks (ever). Place it on something non-conductive (paper? the box it came in?)
  • Insert the SD Card
  • Connect an Ethernet cable between the Pi and your computer.
  • Now plug in the power.

Log In

Back on your computer, in the terminal, run:

ssh pi@raspberrypi.local

You'll get asked if you trust this new host. Type yes and hit return.

Then you'll get asked for the password. It's raspberry.

The authenticity of host 'raspberrypi.local (192.168.2.2)' can't be established.
ECDSA key fingerprint is SHA256:13XNzKJHbLc3wizLJMlrMbhtnj2cRRcQXdF9iG4umUE.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'raspberrypi.local,192.168.2.2' (ECDSA) to the list of known hosts.
pi@raspberrypi.local's password:
Linux raspberrypi 4.14.34-v7+ #1110 SMP Mon Apr 16 15:18:51 BST 2018 armv7l

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

SSH is enabled and the default password for the 'pi' user has not been changed.
This is a security risk - please login as the 'pi' user and type 'passwd' to set a new password.

pi@raspberrypi:~ $

You're in!

Update and Install Basics

This will ensure you have the latest version of all the installed packages.

sudo apt-get update
sudo apt-get dist-upgrade

Depending on how old the image you downloaded is, this could be quick or take some time.

Now install the minimal things needed to be able to run a graphical desktop. You'll use this graphical desktop when you connect to the Pi from your computer. This makes working in PureData or SuperCollider nice. Because we're seting it up minimal, when you run headless, the desktop will not be running, and the audio programs will run without visual UI.

Run these two commands. Don't be clever and combine them:

sudo apt-get install --no-install-recommends \
    screen vim \
    git make \
    xserver-xorg xinit \
    realvnc-vnc-server
sudo apt-get install raspberrypi-ui-mods

Swap emacs for vim if you prefer. You'll get asked if you want to proceed ('Y', of course). These two commands will download well over a hundred packages.

Run:

sudo rasp-config

You can move around this menu structure setting things. Here are a few you need to set:

1. Change User Password

change it now! To something you'll remember.

Then make these settings, using arrows to select options, tab to move between menus and buttons, and enter to select:

3. Boot Options
    B1 Desktop / CLI
        B3 Desktop

4. Localisation Options
    I2 Change Timezone
        -- pick your timezone

4. Localisation Options
    I4 Change Wi-fi Country
        -- pick your country

5 Interfacing Options
    P3 VNC
        Yes    (use arrow keys to select)

7. Advanced Options
    A3 Memory Split
        16

7. Advanced Options
    A5 Resolution
        1600x1200   (or whatever you like, but the default is too small!)

Then [tab] key to Finish, hit return, then select Yes to reboot.

Graphic Login

On your computer, install RealVNC Viewer

Run it and connect to your Pi (raspberrypi.local). You'll need to enter login information twice - once to RealVNC... and then once to the Pi screen that comes up.

Play around with the desktop if you like. Customize the colors and background image.

From the big raspberry icon on the task bar, Shutdown the pi...

Whew!

You've got the Pi set up as a minimal system that can have a desktop if you like, or will just boot up without a display if needed.

That was the hard part... getting audio set up is going to be much easier!

Assemble the Pisound

Follow the instructions on Blokas' web site: Getting Started.

If assembling the case, pay attention to the height of the standoffs - there are short and long ones, and the short ones go on the bottom. Also the bottom plate may need to be fliped over as the two sides aren't exactly the same. Try fitting the long side pieces in before screwing all down to see which way it goes.

Leave the SD Card in - it is really hard to insert it once you start assembling the case.

Once it is all assembled, connect the network again, then power it back on.

Pisound Software

1. Install Pisound Drivers

Blokas provides an installer script. They have you download it directly into the shell so it runs immediately. That always makes me nervous, so I do it this way:

Log into the Pi via RealVNC. On the task bar, click the screen icon (has ">_" symbol) to open a shell. Run this:

curl -O https://blokas.io/pisound/install-pisound.sh
less install-pisound.sh   # look at it and see if it sensible
sh install-pisound.sh
rm install-pisound.sh

If you are adventurous, you can do it in one step:

curl https://blokas.io/pisound/install-pisound.sh | sh

In either case, you may have to enter your password, since installation runs with sudo.

At the end of the script it suggests:

Now you may run sudo pisound-config to customize your installation!

Hold off!, we will install the music software manually to ensure it is minimal.

2. Verify Drivers

You can verify that the drivers are installed, and that the Pisound hardware is all operating with the O.S.

Run this to see the list of audio output devices:

aplay -l

You should see this, with pisound listed in the list:

**** List of PLAYBACK Hardware Devices ****
card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 7/7
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
card 0: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: pisound [pisound], device 0: PS-2DES12E snd-soc-dummy-dai-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0

Run this to see the list of audio input devices:

arecord -l

You should see:

**** List of CAPTURE Hardware Devices ****
card 1: pisound [pisound], device 0: PS-2DES12E snd-soc-dummy-dai-0 []
  Subdevices: 1/1
  Subdevice #0: subdevice #0

Run this to see the list of MIDI devices:

aconnect -l

You should see this:

client 0: 'System' [type=kernel]
    0 'Timer           '
    1 'Announce        '
client 14: 'Midi Through' [type=kernel]
    0 'Midi Through Port-0'
client 20: 'pisound' [type=kernel,card=1]
    0 'pisound MIDI PS-2DES12E'

If you have some USB MIDI devices plugged in, you'll see them in that list, too!

Music Apps

PureData

Install with:

sudo apt-get install --no-install-recommends puredata gem

Note: This is a much smaller install than what the pisound-config installs. For some unknown reason, the package for gem recommends pulling in a full PDF rendering system! Hence, the --no-install-recommends.

SuperCollider

You have two choices... install version 3.7.0 which is in the package repos. This is easy, but a little older.

Or compile it yourself, but that's a bit harder and will take an hour or more.

Just install it...

Install with

sudo apt-get install --no-install-recommends supercollider

Note: This is a much smaller install than what the pisound-config installs.

You will get a dialog box with a lot of text, asking you, at the end "Enable realtime process priority?". Choose

Yes

Set up

Unlike PureData, which can talk directly to the alsa audio drivers, SuperCollider talks to jackd, which in turn talks to alsa. You can let SuperCollider handle starting and stopping jackd for you, but you need to set it up.

Edit (vi or emacs or nano) the file ~/.jackdrc to have the following single line:

/usr/bin/jackd -R -P 75 -d alsa -d hw:pisound -r 48000 -n 2 -p 64 -s

Run it

scide

Once running, you need to boot a server: From the Language menu, choose Boot Server. You'll see some text which should let you know that jackd is running with ALSA.

Then type some SuperCollider code into the big, Untitled window, select it, and choose Language menu > Evalutate Selection, Line, or Region. (Or type [CTRL+Return])

Try this lovely snippet from Fredrik Olofsson:

play{q=SinOsc;a={|x...y|perform(x,\ar,y)};Splay ar:a.(CombN,c=a.(q,0,a.(Blip,1/f=(1..8),888/a.(q,1/88,0,2,3).ceila.(Duty,a.(q,1/8)>0+2*1/8,0,Dseq([8,88,888],inf)))188),1,8-f/8,8)/8+a.(CombN,a.(GVerb,a.(BPF,8e=c.mean,88,1/8),88),1,1)+a.(q,88,0,a.(q,0,e)<0/88)}// #SuperCollider

He's @redFrik on twitter, and he posts many great short compositions you can play in SuperCollider.

To stop, Language > Stop. (or just [CTRL+.].)

If you want to test input effects processing, try this:

{
    var fast = SinOsc.kr(12) * 2;      // +/- 2 semitones at 12Hz
    var slow = SinOsc.kr(0.2) * 24;    // +/- 2 octaves at 1/5Hz
    var center = 60;                   // around middle C
    var filtFreq = (fast + slow + center).midicps;

    var input = SoundIn.ar();
    var resonated = Resonz.ar(input, filtFreq, bwr:0.15);
    var reverbed = FreeVerb.ar(resonated, room:0.8);

    reverbed   // last thing returned is played out
}.play

Done!

Play music, have fun, and let me know how it went!

  • Mark

Things Still to Figure Out and Add

WiFi

two ways to set up WiFi

- raspi-config if you want it to connnect
- pisound-config if you want the button to launch a hotspot

  • set up static ip by editing /etc/dhcpcd.conf (optional):

    interface eth0

    static ip_address=192.168.42.6/24 static routers=192.168.42.1 static domain_name_servers=8.8.8.8 8.8.4.4

    • reboot, re-log in

Nicer terminal

sakura

Setting up the Btn for SuperCollider scripts

The default PureData patches don't work with the Button

[] Pressing the button after installing PureData fails because it loads the wrong file. It tries to load

/usr/local/puredata-patches/GarageBeat/_main.pd

But that patch needs to start with:

/usr/local/puredata-patches/GarageBeat/0_START.pd

Turn off the Screen Saver

use the menu > Preferences > ScreenSaver setting

or, maybe also

edit ~/.config/lxsession/LXDE-pi/autostart, comment out the @xscreensaver line like so:

@lxpanel --profile LXDE-pi
@pcmanfm --desktop --profile LXDE-pi
#@xscreensaver -no-splash
@point-rpi

note about cron & anacron

need to measure if auto login really eats any significant CPU when headless

should figure out if changing the memory split really matters or not

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