Posts tagged: Autostatic

Automated Raspberry Pi audio recorder

Today we’re gonna roll our very own sound recorder using a Raspberry Pi

Raspberry Pi Audio Recorder

This tutorial will show you how to build a fully automated recorder using an RPi, a USB sound card and a USB drive.

First up; install Raspbian, make sure it defaults to the command line and/or has SSH access so you can login to it from another computer. There’s plenty of tutorials out there explaining how to do this.

Second; make sure you have a compatible sound card, (I used a spare Griffin iMic, any class compatible one should work) and a USB flash drive. It should be possible to write to the SD card you’re using on the RPi, but people have had problems going that route. Besides, using a fat32 formatted usb drive will ensure you can plug it into you computer and play or copy the sound files without having to login (ssh) to the RPi.

First we’re gonna get rid of a lot of unwanted stuff! This isn’t a complete list, but I’m sure we can live without these applications installed taking up precious CPU cycles, RAM and disk space. Note: This will completely wipe the graphical user interface. You won’t be able to use the desktop anymore!

$ sudo apt-get purge galculator idle3 idle idle-python3.2 python3 midori scratch xpdf midori dillo netsurf-common netsurf-gtk leafpad penguinspuzzle pistore gpicview heirloom-mailx wpasupplicant aptitude xarchiver omxplayer aspell usbmuxd debian-reference-common debian-reference-en python-picamera cups-bsd cups-common vim-common vim-tiny desktop-base lightdm lxappearance lxde-common lxde-icon-theme lxinput lxpanel lxpolkit lxrandr lxsession-edit lxshortcut lxtask lxterminal obconf openbox raspberrypi-artwork xinit xserver-xorg xserver-xorg-video-fbdev xserver-common xserver-xorg-core xserver-xorg-video-fbturbo x11-common x11-utils x11-xkb-utils xauth xfonts-encodings xfonts-utils oracle-java7-jdk aptitude-common python python-gi python-minimal python-pifacecommon python-pifacedigitalio python-rpi.gpio python-serial python-support python2.7 python2.7-minimal python3.2 python3.2-minimal

Followed by:

$ sudo apt-get autoremove


$ sudo apt-get autoclean

That’s a lot of stuff we won’t be using! Now, we’re gonna install what we do want:

$ sudo apt-get install sox libsox-fmt-mp3

Sox is a specialized recording, processing and playback application. I won’t go into it too much, but it fits our needs perfectly. The second, libsox-fmt-mp3, is a library so we can encode to MP3 (if that’s what you want).

Now that we deleted and installed what we need, let’s set-up the soundcard. First up, let’s kill the built-in sound card:

$ sudo nano /etc/modules

And comment out:


By putting a “#” in front of it. Like so:

# snd-bcm2835

To be sure USB is first in line, we’re gonna force ALSA to pick it over the built-in one, even if we’ve just killed it.

$ sudo nano /etc/modprobe.d/alsa-base.conf

And comment out:

options snd-usb-audio index=-2

Again, with a “#” like this:

# options snd-usb-audio index=-2

Last but not least enter:

$ alsamixer

And set the recording levels of your soundcard to how you like them by pressing F4. To make sure the Raspberry Pi always boots up with these sound settings, enter this in the command line:

$ sudo alsactl store

Make a folder to mount the USB stick in:

$ sudo mkdir /mnt/USB/

Now we’re gonna make a few scripts. Don’t be afraid if you’ve never done this before, I’ve pre-fabricated them for you! In your home folder (Type “cd” and hit enter if you’re not certain), type:

$ mkdir Scripts

This’ll make a neat little folder for you to put scripts in. Change into it by typing:

$ cd Scripts/


$ nano

Copy and paste the following into it.

## Created by Son of 8-Bits
## Borrowing parts from Autostatic

## Mount the USB stick and kill unwanted services

## mount the USB stick
sudo mount -t auto /dev/sda1 /mnt/USB

## Stop the ntp service
sudo service ntp stop

## Stop the triggerhappy service
sudo service triggerhappy stop

## Stop the dbus service. Warning: this can cause unpredictable behaviour when running a desktop environment on the RPi
sudo service dbus stop

## Stop the console-kit-daemon service. Warning: this can cause unpredictable behaviour when running a desktop environment on the RPi
sudo killall console-kit-daemon

## Stop the polkitd service. Warning: this can cause unpredictable behaviour when running a desktop environment on the RPi
sudo killall polkitd

## Kill the usespace gnome virtual filesystem daemon. Warning: this can cause unpredictable behaviour when running a desktop environment on the RPi
killall gvfsd

## Kill the userspace D-Bus daemon. Warning: this can cause unpredictable behaviour when running a desktop environment on the RPi
killall dbus-daemon

## Kill the userspace dbus-launch daemon. Warning: this can cause unpredictable behaviour when running a desktop environment on the RPi
killall dbus-launch

## Set the CPU scaling governor to performance
echo -n performance | sudo tee /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor


Press “ctrl+x” to exit, “Y” to save, followed by an enter. You should now be back in the command line. This script will automatically mount your USB drive in /mnt/USB/ and kill some unwanted services clogging up RAM and CPU cycles. Most of this script was made by Autostatic, check out his original work here.

Now for the recording script:

$ nano


## Created by Son of 8-Bits
## 48000Hz stereo MP3 at 320kbps that automatically stops recording after 1 minute of silence.

FILENAME=$(date +”%Y%m%d_%H%M”)

sudo rec -c 2 -r 48000 -C 320.99 –buffer 262144 /mnt/USB/${FILENAME}.mp3 silence 1 0.1 1% 1 1:00 1%

[ $? -eq 0 ] || exit $?

sleep 10

sudo shutdown now


ctrl+X, Y, enter

To make these scripts work as planned enter:

$ sudo chmod 755

But these scripts won’t start by themselves just by being there! To make them start at boot type:

$ sudo nano /etc/rc.local

On the empty line after “# By default this script does nothing.” add:

sudo /home/pi/Scripts/
sudo /home/pi/Scripts/

ctrl+X, Y, enter

BAM! You’re done!

Try it out by hooking up a sound source to the line-in of your soundcard, booting the Pi, and recording a part of whatever it is you want to record. Note that after one minute of silence the RasPi will shut itself down. Listen back what you’ve just recorded by unplugging the USB flash drive and plugging it in you computer. Here are some tips if things are not to your liking.

Volume too low or high? Check the part about Alsamixer. (And don’t forget to check the level coming out of your audio source as well!)
Like to stop sooner (or later) after silence sets in, edit the recording script. See the part that says “1:00”? This is 1 minute, edit it to your liking. For instance ‘0:30’ for 30 seconds or ‘2:00’ for 2 minutes.
Pi not getting enough power? Use a 2 ampere powerplug or put a powered USB-hub between the RasPi and the soundcard/USB stick.



First ever Raspberry Pi Jam (the Netherlands)

September 26th was the first ever Dutch Raspberry Pi Jam at Ordina


Short version: Raspberry Pi & Arduino-fest 2013. Embedded systems and micro-controllers everywhere!

Longer version: Gert van Loo was there, known from the Gertboard, telling us about the process of how the Raspberry Pi came to be. There were (quite a few) representatives from Bitlair, a ‘hackerspace‘ located in Amersfoort, (edit:) and Rev Space located in The Hague (/edit) showing their awesome hacking skills. Like this old military telex connected to twitter showing all the tweets hash-tagged #RasPiNL. Awesomely steampunk, don’t you think?

Tim Becker was a speaker who gave a presentation about Anykey0x. What is Anykey you ask? One button to rule them all! Need a designated “ë” button on your keyboard? This button provides! .. Well, that’s how it started out and it has grown out to be programable micro-controller similar to Arduino, but much simpler in it’s premise, yet it’s a little faster so it should be able to do a little more. And I for one like it’s noob-friendly features: You can’t brick the little device by writing bad code, cause the boot-loader is written in ROM! Thank you Tim! So I decided to get one myself. A few examples of what you could do: Make a joystick track your mouse-pointer, run midi-commands (OSC would work as well but beware, check the maximum binary size!) or make led’s blink (…duh!). With some work you could, as far as I’ve understood, make a working audio interface out of it which could perhaps provide the Raspberry Pi with a better audio output then the current build-in one. A device this small could easily be patched onto the RasPi. I did mention it was small right? Well, this is what it looks like:

And last but certainly not least was Jeremy from Autostatic who gave a live demo of what the Raspberry Pi can do using real-time audio software. Using (Debian) applications like Samplv1 and a virtual guitar-effect box playing live guitar. Jeremy has done a lot of work to get audio software like Jack running with low-latency and has build applications from source for the Raspberry Pi’s ARMHF CPU architecture, sometimes working together with the coders of the original source to get things working. Most if not all of his work on the Pi can be installed via the audio repository he is maintaining. To install the repository on your Debian (Raspbian) system head on over to, and follow the procedures. From there you can look up all kinds of useful audio-applications like Synthv1, Non-Sequencer, and much, much more!

All in all it was a great day, and there was just too much to sum up here. Like a robot playing chess, pi-cameras making time-lapse images or providing an easy way to tweet your new hairdo , there was even a programming workshop to get you started with the Scratch programming environment. I think this day inspired many new projects and I hope we can see more innovative workshops, seminars and conferences like this. And for that we thank Ordina for hosting this event. (Hopefully,) see you at the next one!