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README.md
 
 

README.md

quick general course introduction

131017

raspberry pi overview, introduction, ssh login, getting around and making sound

  • raspberry pi is a cheap computer than can run linux (meaning you can also run supercollider)
  • really good video playback
  • ok for connecting sensors and controlling leds+motors etc.
  • sound support is not so good unfortunately (low sound quality, noise, hickups)
  • lots of material online - books, reference projects, blogs, forums

demo projects

//--4 channel video player

for the dance piece Ich(a) by Zufit Simon (https://www.tanzforumberlin.de/produktion/icha/) i needed a way to send out 4 separate hi-quality video streams. the videos didn't need to play back in frame sync, but they had to have a manual trigger to go to black and start the next video. on the board is a small python program that starts automatically. it reads a button and uses omxplayer to cycle between mp4 files. the black out is just a short mp4 with only black frames.

see https://fredrikolofsson.com/f0blog/cheap-4-channel-videoplayer/ for the python code and installation instructions.

//--96 channel pwm led driver

for the piece redAlert to be premiered in stockholm 9nov i wanted to control hundreds of leds. i built three boxes with raspberry pis that could drive 32 channels each. i control them from supercollider with osc via wifi. here i used model A because it is cheaper but mainly because it requires less current. without the leds the rpi + wlan + driver circuit draws 360mA. with all the 32*3 leds turned on it's 1000mA total.

see https://fredrikolofsson.com/f0blog/redalertlight/ for schematics, code and pictures.

setting up a raspberry pi

//--operating systems

there are many different systems you can run on a raspberry pi. most of them are linux distributions build on debian. i can recommend the standard raspbian https://www.raspberrypi.org/software/operating-systems/

or for a minimal headless (no windows, gui etc - only terminal) install you can try moebius http://moebiuslinux.sourceforge.net

and another system with preinstalled music software is satellite https://ccrma.stanford.edu/wiki/Satellite_CCRMA_First_Steps

//--minimum requirements

below is what's required for booting up and logging in via ssh.

  • a raspberry pi. i recommend a model B to start with. this is the most common one and easiest to get started with. model A lacks ethernet and that makes it harder to install new software and communicate with (can be solved with a wlan usb dongle). often i use a model B for developing and then when the system/code is finished, i move the sd card over to a model A. just watch out for the ram memory difference (512 vs 256mb).
  • a power 5v supply with micro usb connector that can provide >700mA. it might work to power it from your laptop (max 500mA) but that's not a good idea. maybe you already have an usb charger that can be used.
  • ethernet cable
  • sd card of 4gb or more. 4gig is plenty and very rarely will you need a bigger one. also don't care much about different sd card classes and speeds (extreme, 2, 4, 6, 10 etc). write speed won't make such a big difference. instead it's better to get a card from a good brand - stay away from cheap no-name brands.

additional stuff if you want to use it like a standalone computer...

  • usb keyboard and usb mouse
  • hdmi cable and screen/projector (also works with rca composite video)
  • usb hub
  • usb soundcard

//--basic preparation and startup

you will need to do a few things before booting the pi for the first time...

  • download an operating system (here we will use Raspbian)
  • put the os on a sd card (on osx it is easiest with Pi Filler http://ivanx.com/raspberrypi/)
  • connect ethernet and 5v power to the pi
  • find the ip address of the rpi (on osx it is easy with the free app lanscan https://www.iwaxx.com/lanscan/), or look in your router settings (web admin/settings pages).
  • (on osx you can also connect the pi directly to you mac via ethernet and turn internet sharing on. then figure out the ip with lanscan or ping broadcast.)

logging in for the first time:

  • ssh pi@192.168.1.53
  • default password for raspbian is raspberry
  • sudo raspi-config and select expand file system and optionally change password. then select finish and let the rpi reboot.
  • after reboot log in again with ssh
  • sudo apt-get update to go online and check for software updates
  • sudo apt-get upgrade to install any software updates (these two are good to run once in a while)

ssh troubleshooting:

  • if you get ssh: connect to host 192.168.1.11 port 22: Operation timed out then likely the ip is wrong or the rpi isn't powered.
  • if you get WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! on your laptop while trying to log in then no worries. just reset the ssh key with the following command.
  • ssh-keygen -R 192.168.1.53

//--running sc on rpi raspbian

install 2013-09-25-wheezy-raspbian.img like above and also update to get sc+jack (sudo apt-get update; sudo apt-get upgrade)

  • $ ssh pi@192.168.1.53
  • $ jackd -P 95 -p 32 -d dummy -C 1 &
  • $ alsa_out -d hw:1 2>&1 > /dev/null & use hw:1 for usb soundcard, and hw:0 for internal onboard sound
  • $ sclang
  • > s.boot
  • > "jack_connect SuperCollider:out_1 alsa_out:playback_1 &".unixCmd
  • > "jack_connect SuperCollider:out_2 alsa_out:playback_2 &".unixCmd
  • > a={SinOsc.ar([400,404],0,0.1)}.play
  • > a.release
  • > 0.exit
  • $ pkill jackd

notes:

  • lines beginning with a $ means terminal
  • lines beginning with a > means it's within sclang and should be executed with a ^L+return in the end (ctrl+L on osx).

//--links

some random projects...

some getting started guides...