hi all, here is an up-to-date tutorial to make an analog synth with a Raspberry Pi and pd :
- installing raspbian on a SD card
see instruction : http://www.raspbian.org/ http://elinux.org/RPi_Easy_SD_Card_Setup
connect a keyboard, a mouse, an HDMI screen and an ethernet cable with DHCP (to get internet access) and boot on the SD card to configure the OS :
- expand root
- change keyboard
- change password
- change local (fr utf8)
- change memory split : minimum allocated to video
- enable ssh
- boot : no desktop
- update
sudo apt-get update / upgrade sudo reboot log in and start graphical interface : startx
- installing puredata
sudo apt-get install git tk8.5-dev libasound2-dev subversion downloading latest pd :
git clone git://pure-data.git.sourceforge.net/gitroot/pure-data/ pure-data cd pure-data/src autoconf ./configure CFLAGS="-mfpu=vfp -mfloat-abi=hard" make sudo make install
It takes around 20min to build, be patient. you can start pd using the « pd » command
- optimising the system for pd :
sudo leafpad /etc/security/limits.conf or try nano if you don’t start an X server add
- rtprio 99
- memlock 1000000000
start pd and go to media > preference > startup add the following flag in the startup flag field : -rt -alsa -noadc -audiobuf 25
then apply and restart pd.
- test
download analog synth emulation patch by Cyrille Henry here : svn checkout https://pure-data.svn.sourceforge.net/svnroot/pure-data/trunk/externals/nusm... cd ~/nusmuk-audio make cd examples pd analog_synth_emulation.pd
- Performance :
The analog output is very poor now. Some (like Miller) are working on improving it (thanks for their work). The signal to noise ratio is low and there is also some quantization distorsion.
On the other hand, one can output some audio through HDMI. We use an HDMI display to convert audio and to send it to good quality loudspeaker. We later tried a USB soundcard (Edirol UA-1A) which works out-of-the-box.
We tried to reduce latency without hearing click with the Cyrille’s patch, here are the results : 10 ms latency with USB soundcard 20 ms latency with integrated HDMI audio We also tried to input audio with USB soundcard but audio is crackly as soon as input is enable (with output too).
- Getting data from real world
Most of MIDI-USB interface should work out-of-the-box. With Edirol UM-1EX we get a MIDI loopback between 30 and 35ms.
HID works great. svn checkout https://pure-data.svn.sourceforge.net/svnroot/pure-data/trunk/externals/hid/... cd hid/ make pd hid-help.pd
The Byron interface (http://www.1010.co.uk/org/byron.html) is one of the cheapest way to make a CV-to-computer interface.
A TCP loop on a local computer takes less than 1.5 ms.
- Autologin
To enable auto login, we follow this : http://elinux.org/RPi_Debian_Auto_Login. And to start pd at startup, we follow the steps on the same page but replace startx by ~/autostart.sh wich is a script like this : pd -nogui -audiodev 3 -open ~/nusmuk-audio/examples/analog_synth_emulation.pd