raspberrypiWorkshop

held at ems 9oct2016, organized by vems

in this 3h workshop we will install the raspbian operating system from scratch, install pure data and supercollider and last look at how to connect an arduino board and send data to/from it and the raspberry pi.

participants should bring:

• laptop - preferably with sd card reader/writer
• micro sd card - 8gb or larger
• raspberry pi - model 1b, 2 or 3
• power supply - 5v micro usb for the rpi
• headphones with minijack
• ethernet cable
• arduino with usb cable

additional: (but not necessary)

• usb sound card
• usb wlan module
• breadboard, sensors, leds, wires

overview

these are the steps we will go through. it may look complicated but in practice there are only a few things one need to do. and after you've gone through it once, you should be able to perform it all again in <15min.

details are writting in italic.

1. burn raspbian to your sd card
2. start your raspberry pi
3. log in to your raspberry pi
4. setup raspbian
5. [setup wifi](#setup wifi)
6. install pure data
7. install supercollider
8. tune your audio
9. autostart
10. communicate with arduino
11. useful terminal commands
12. shutdown

burn raspbian to your sd card

1. download the latest raspbian image
   • or copy the zip from the provided usbstick
   • to save space you can use the .zip file directly without unpacking the .img
   • here we use 2016-09-23-raspbian-jessie - not the 'lite' version
   • jessie 'lite' will fit on a smaller sd card and is useful for non-gui audio-only headless systems
2. download etcher.io
   • works on osx, linux, windows
   • on osx you can also use pifiller
3. start etcher and select the raspbian zip file
4. insert your 8gb sd card
5. click flash
   • on my machine the process takes ~9min
6. if you are using a raspbian image newer than 2016-11-25 make an empty file called 'ssh' on the sd card
   • for security reasons ssh is no longer enabled by default

start your raspberry pi

1. put the sd card in your raspberry pi
2. connect the ethernet cable to your raspberry pi
   • the other end goes to your home wlan router or to your laptop
   • if you connect to a osx: go to system preferences / network and activate internet sharing - share from wifi to ethernet
   • if you connect to a windows machine: see here
3. connect 5v micro usb power supply
   • always connect power last
   • and never pull the power without properly shutting down the system (see below)
   • on first boot the rpi will automatically expand the file system to make full use of the sd card

log in to your raspberry pi

1. wait a bit after applying 5v
   • specially on first boot it will take a while to connect to the network
2. find your raspberry pi on the network and take note of the ip address (e.g. 192.168.1.52)
   • we want to see that it is accessible and which ip address it got assigned
   • to find out you can log in to your router's admin setup panel
   • or open terminal and type arp -a to list connected devices
   • or on osx you can use lanscan
3. open a terminal window and type ssh pi@192.168.1.52 (or whatever ip you found for your rpi)
   • on osx terminal is found in your applications/utilities folder
   • on windows you can install putty
   • if you get a warning about 'remote host identification' first do ssh-keygen -R 192.168.1.52
   • instead of the ip you can also use ssh pi@raspberrypi or pi@raspberrypi.local
4. the default password 'raspberry'
5. make sure you can log in like in the picture below
6. then type exit to leave

setup raspbian

1. log in again using ssh
   • via terminal or putty - see #3 above
2. type sudo raspi-config
3. select change user password and enter a new password
4. select change hostname under advanced options and enter a new name
   • this is so that you can identify your raspberry pi on the network
   • then use ssh pi@mynewhostname to log in
5. optional: change memory split under advanced options
   • if you run headless and never use gui you can set this to the lowest (16)
   • if you will do graphics (e.g. with openframeworks) set this to a higher value (256)
6. optional: enable vnc under advanced options
   • so that you can use the gui remotely with vnc viewer - see under setup wifi below
   • install real's vnc viewer
7. finish and reboot

setup wifi

1. log again in via ssh

   • note: use the new hostname (see #4 above) and new password

2. type sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

3. type or copy/paste the following at the bottom

   network={
       ssid="wifiname"
       psk="password"
   }
   

4. press ctrl+o to save and ctrl+x to exit

5. restart with sudo reboot

   • the raspberry pi should now reboot and try to connect to the wifi network - check with lanscan or in your router's setup panel like before
   • if the raspberry pi could connect to wifi, you can now disconnect the ethernet cable

6. optional: start real's vnc viewer and try to connect to your raspberry pi

   • download it from here
   • make sure you have activated vnc in raspi-config - see above

reference: setting up wifi via command line

install pure data

first make sure your raspberry is connected to the internet and then do the following.

1. sudo apt-get update

2. sudo apt-get install puredata

3. apt-cache search "^pd-" (this will just list libraries and externals)

4. sudo apt-get install pd-comport pd-cyclone (this will install two libraries that we need for arduino below)

5. nano testsines.pd and copy/paste in the following

   #N canvas 1068 88 450 300 10;
   #X obj 238 159 dac~;
   #X obj 235 73 osc~ 400;
   #X obj 289 73 osc~ 404;
   #X msg 126 154 \; pd dsp 1;
   #X obj 126 83 loadbang;
   #X obj 126 123 del 100;
   #X text 42 122 important ->;
   #X obj 238 111 *~ 0.2;
   #X obj 280 111 *~ 0.2;
   #X connect 1 0 7 0;
   #X connect 2 0 8 0;
   #X connect 4 0 5 0;
   #X connect 5 0 3 0;
   #X connect 7 0 0 0;
   #X connect 8 0 0 1;
   

6. press ctrl+o to save and ctrl+x to exit

7. pd -stderr -nogui -verbose -audiodev 4 testsines.pd (test different audiodev - 4 is usually the usb soundcard)

8. you should hear two sine tones

   • note: if you are using the build-in headphones output (audiodev 0) you should turn up the volume to 100 with alsamixer (see tune your audio below)

9. stop with ctrl+c

10. nano testmic.pd and copy/paste the following

    #N canvas 1068 88 450 300 10;
    #X obj 238 230 dac~;
    #X msg 126 154 \; pd dsp 1;
    #X obj 126 83 loadbang;
    #X obj 126 123 del 100;
    #X text 42 122 important ->;
    #X obj 238 24 adc~;
    #X obj 238 53 delwrite~ del1 500;
    #X obj 238 123 delread~ del1 500;
    #X obj 259 80 delwrite~ del2 750;
    #X obj 280 144 delread~ del2 750;
    #X obj 238 182 *~ 0.2;
    #X obj 280 182 *~ 0.2;
    #X connect 2 0 3 0;
    #X connect 3 0 1 0;
    #X connect 5 0 6 0;
    #X connect 5 1 8 0;
    #X connect 7 0 10 0;
    #X connect 9 0 11 0;
    #X connect 10 0 0 0;
    #X connect 11 0 0 1;
    

11. press ctrl+o to save and ctrl+x to exit

12. pd -stderr -nogui -verbose -audiodev 4 testmic.pd (test different audiodev - 4 is usually the usb soundcard)

13. if you have a soundcard with a mic connected you should hear an echo effect

    • note: this example will not make any sound if you try it with the built-in audio - there is no sound input on the raspberry pi

14. stop with ctrl+c

reference: https://fredrikolofsson.com/f0blog/pd-on-raspberry-pi/

and if you connect a monitor+keyboard or log in via vnc, you can also also patch pd like normal. just start pure data from the menu on the left hand side (under sound & video). set up your audio under 'Media' in the menu bar.

install supercollider

just follow the instructions under installation and headless here... https://github.com/redFrik/supercolliderStandaloneRPI2

(or if you are using an older rpi1 or a rpi0 here https://github.com/redFrik/supercolliderStandaloneRPI1 )

if you connect a monitor+keyboard or log in via vnc, you can also use the supercollider ide like normal. follow the instructions under startup on the github page linked above.

tune your audio

by default the alsa volume on raspberry pi is quite low. it's recommended to turn it up so that you can lower the amplifier on the output and thereby get a less noisy signal.

alsamixer

and to make the settings permanent do...

amixer controls #and check which numid is ’Master Playback Volume’
amixer cset numid=1 100% #adapt this value
sudo alsactl store

autostart

to make puredata start the testsines.pd patch at startup do

1. open terminal and type crontab -e

2. scroll down and add the following line (edit to match your audio device and path)

   @reboot /usr/bin/pd -stderr -nogui -audiodev 4 /home/pi/testsines.pd
   

3. press ctrl+o to save and ctrl+x to exit

4. sudo reboot

and now you should hear the sines after the rpi booted. to stop log in and type pkill pd

to autostart supercollider see the github page linked above.

arduino

program an arduino from your laptop with the following

//arduino code testarduino.ino
void setup() {
    Serial.begin(57600);
}
void loop() {
    int val = analogRead(A0);
    Serial.write(253);
    Serial.write(254);
    Serial.write(val>>8);
    Serial.write(val&255);
    Serial.write(255);
    delay(100);  //update rate
}

and then on the rpi open terminal and type

apt-cache search "^pd-" #just list libraries and externals
sudo apt-get install pd-comport pd-cyclone #just if you did not do it above

then nano testarduino.pd and copy/paste the following

#N canvas 141 95 450 300 10;
#X msg 86 31 devices;
#X obj 86 61 comport 1 57600;
#X obj 86 95 cyclone/match 253 254 nn nn 255;
#X obj 86 140 unpack f f f f f;
#X obj 140 176 << 8;
#X obj 140 202 +;
#X floatatom 140 230 5 0 0 0 - - -, f 5;
#X connect 0 0 1 0;
#X connect 1 0 2 0;
#X connect 2 0 3 0;
#X connect 3 2 4 0;
#X connect 3 3 5 1;
#X connect 4 0 5 0;
#X connect 5 0 6 0;

connect the arduino to the rpi via usb and run the pd patch with

pd -stderr -nogui -verbose -audiodev 4 testarduino.pd

you should see (and hear) values in the range 0-1023 depending on the voltage present on pin A0. stop with ctrl+c.

for supercollider use this code (testarduino.scd)...

(
s.waitForBoot{
   var syn, ser, r;
   syn= {|freq= 0| SinOsc.ar([400, 404]+freq, 0, 0.2)}.play;
   ser= SerialPort("/dev/ttyUSB0", 57600);
   r= Routine.run({
      var val;
      inf.do{
         var data= [];
         var d= 0;
         while({d!=255 and:{d.size<100}}, {
            d= ser.read();
            data= data++d;
         });
         if(data[0]==253 and:{data[1]==254}, {
            val= (data[2]<<8)+data[3];
            syn.set(\freq, val);
            val.postln;
         });
      };
   });
   CmdPeriod.doOnce({ser.close});
};
)

and also let's try python. open terminal and type nano testarduino.py and paste in the following code

import serial
ser= serial.Serial('/dev/ttyUSB0', 57600)
while True:
    indata= []
    d= ''
    while (d!='\xff') and (len(indata)<100):
        d= ser.read()
        indata.append(d)
    if (indata[0]=='\xfd') and (indata[1]=='\xfe'):
        hibyte= ord(indata[2])
        lobyte= ord(indata[3])
        val= (hibyte<<8)+lobyte
        print val

start it with python testarduino.py and stop with ctrl+c

shutdown

to safely turn off your raspberry pi you need to log in and type:

sudo halt -p

then wait for the led on the board to blink 10 times. now you can disconnect the 5v micro usb cable. if you don't power down the system in this way you risk corrupting the sd card.

another option is to add your own button to run a halt script when pressed. below is one way to do this using a python script that always run in the background.

1. log in and type nano shutdown.py

2. type or copy/paste the following

   import sys
   from os import system
   from time import sleep
   import RPi.GPIO as GPIO
   pinoff= 3
   GPIO.setmode(GPIO.BOARD)
   GPIO.setup(pinoff, GPIO.IN)
   while True:
       if GPIO.input(pinoff)==0:
           system('sudo halt -p')
           sleep(10)
           sleep(0.5)

3. press ctrl+o to save and ctrl+x to exit

4. type crontab -e and add the following to the bottom @reboot /usr/bin/python /home/pi/shutdown.py

5. sudo reboot, wait for a bit and then connect a cable/button between pin 3 (aka bcm2) and ground. see https://pinout.xyz

copy files to & from rpi

one way is to use scp (secure copy) in your laptop terminal.

to copy a file from your laptop desktop to rpi desktop directory type:

scp ~/Desktop/myfile.pd pi@192.168.1.52:Desktop

to copy another file from your rpi home directory to your laptop home directory type:

scp pi@192.168.1.52:testsines.pd ~

to copy a whole folder add the recursive flag -r. for example to move a folder from your laptop documents folder to your rpi home directory type:

scp -r ~/Documents/soundfiles pi@192.168.1.52:

useful terminal commands

ls              #list files
df -h           #disk free
free -h         #ram memory
top             #cpu usage (quit with 'q')
lsusb           #list usb devices
aplay -l        #list available soundcards
exit            #leave ssh
sudo halt -p    #turn off - wait for 10 blinks
sudo reboot     #restart
sudo pkill pd   #force quit on some program
ls /dev/tty*    #see if /dev/ttyUSB0 is there
rm -r sounds    #remove a folder recursively

reference: https://leanpub.com/jelinux/read