How to change password rules on Raspbian

On recent version of Raspbian (I think since the release of January 7th of 2014) the password rules have changed and you can’t use anymore simple password like `pi`.
To enforce this requirement, just change the line 25 of /etc/pam.d/common-password. Remove the obscur keyword and add minlen=2 (or whatever you want).
The line should looks like :
25 password [success=1 default=ignore] pam_unix.so sha512 minlen=2

Check man pam_unix for more options.

How to backup a Raspberry Pi and restore it on a smaller SD card

If you’re using Raspberry Pi, you might know the famous command line utility dd, useful to write a Raspbian image to a blank SD card (cf. http://elinux.org/RPi_Easy_SD_Card_Setup).

You can also use this tool to do backup of the whole disk, but it has two drawbacks :

  1. when you copy the whole disk, the image is as big as the disk, even if the is lots of empty space on it.
  2. when you restore the backup you need a disk at least as big as the original one.

Those two disadvantages lead me to find a solution to make backups smaller and more versatile. The solution I’ll describe here is an adaptation of Ubuntu’s documentation : https://help.ubuntu.com/community/BackupYourSystem/TAR and have been tested on Ubutnu 14.04.

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How to make a RPi boot silent

Here are few modification that allow a very quiet boot, nothing will appear on the screen before the login prompt.
Thus if you start a visual application before that (in /etc/init.d for example) you will not see anything on the screen before your application starts.

First modify the /boot/cmdline.txt like this :
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty3 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=noop rootwait loglevel=3 logo.nologo vt.global_cursor_default=0

here are the details of the changes :
console=tty3 redirect all the post messages to the third console (hit CTRL + ALT + 3 to see them after boot).
loglevel=3 make it less verbose, only errors are reported
logo.nologo disable the RaspberryPi logo on boot
vt.global_cursor_default=0 Disable the blinking cursor.

Moreover you can add disable_splash=1 to /boot/config.txt in order to disable the rainbow splash on power on.

At the en, vous can completly disable the prompt #1 by editing the file /etc/inittab and commenting the following line :
1:2345:respawn:/sbin/getty --noclear 38400 tty1

That’s all !

VLC Network Synchronisation

Here are two command lines to play 2 different video files in sync with VLC.

network clock client :
vlc --network-synchronisation --netsync-master-ip 127.0.0.1 sync-test-rouge.mp4
network clock master :
vlc --network-synchronisation --netsync-master sync-test.mp4

It seems to work only with videos of the same length.
Both audio and video are synchronized. The jitter compensation algorithm take a few time to compensate and after a dozen of seconds all videos are in sync.
It was tested on Ubuntu 13.10 with VLC 2.0.8, the two players on the same machine but it should work over the network.
Also the client must be started before master.

How to upload a sketch to all connected board

For das Körperrauschen project, I use an array of 5 Arduino micro and since they are plugged inside the sculpture, it is not convenient to unplugged them for upgrading one by one. And as I’m a lazy boy I search a way to upgrade them all at the same time. Since they run all the same code, I just made a simple script to upload all the connected board one by one.

Here is the script :

#!/bin/bash

for arduino in /dev/ttyACM* ;
do
ino upload -m micro -p $arduino
sleep 1
done

It searches all serial interfaces that looks like Arduino (/dev/ttyACM* on Ubuntu) and uses inotool to upload the sketch to them. Of course the folder should have the structure required by inotool.
Without delay, I can’t access the next board, and I don’t know why…

(R)Pianophone v0.2

The R(Pianophone) has been upgraded since last year (see http://antoine.villeret.free.fr/?p=427).
Here is the version 0.2 :
(R)Pianophone v0.2
It has a nice 16×2 LCD screen and two push buttons.
The LCD displays Pd patches available on the SDcard and you can go up and down in the list thanks to the buttons.
I also added a USB sound card : ESI UGM96 with 2 inputs (mic and hi-Z) and 2 outputs.

The LCD is a Midas I²C device connected to the Pi through GPIO.
A small command line tool writes on the LCD.

The two buttons are matrixed with the keypad and scanned in an infinite while loop.
When a patch is selected, its name is send through OSC to a main Pd patch and the patch is loaded.

To update the patches on the SDcard, just plug a USB key with some Pd stuff and all patches will be available on the (R)Pianophone.

The USB sound card makes me crazy because of lots of issues.
First I have to disable the ethernet chip to get audio input through USB with this command :
dhclient -r # release DCHP
echo -n "1-1.1:1.0" | sudo tee /sys/bus/usb/drivers/smsc95xx/unbind #disable the cheap

I also need to downgrade to the firmware revision of April 26, 2013.
sudo rpi-update 994e46341bd190ef4ce6ee011e3f9fb8173e2bbf
With the up-to-date firmware, I only got crakles when I disable the ethernet chip (and my USB keyboard goes crazy too…).

Moreover, as the analog synth emulation is eating a lot of CPU, I have to disable the audio input in this patch and to re-enable it the others.
This is done inside Pd by sending those messages to pd :
audio-dialog 2 0 0 0 2 0 0 0 2 0 0 0 2 0 0 0 48000 10 -1 64 to enable
and
audio-dialog 2 0 0 0 -2 0 0 0 2 0 0 0 2 0 0 0 48000 10 -1 64 to disable.
But those messages are not portables. I depends on the alsa configuration. You may find out which command to send by looking to tcl -> pd communication.
To do so, just put a [r pd] connected to a [print] somewhere in your patch and look to the Pd’s console when clicking on “Apply” in the Alsa configuration dialog.

One more thing, is that I got crackles when Pd is loaded directly from /etc/rc.local and I don’t know why…
But a workaround is to start Pd from /home/pi/.bashrc script instead.
It’s a bit crapy since Pd launches every time the pi user logs in and thus several Pd can be loaded at the same time.
But I can’t find a better way to avoid crakles…

RPi osc video player

i’ve just started an OSC video player on the RPi
for now, it’s just an embryo, it plays a demo video file defined in the code,
it’s a proof of concept : it can work but it needs some work
for now the only available feature is the 4 corners perspective correction (intended to be used with a video projector)

and i made a small pd patch to control the player

when i’ll have opportunity, i will add thoses features :
- OSC message to choose video file
- OSC transport control (play, pause, speed, loop…)
- OSC message to choose shader file and control its parameters
- command line arguments to choose video file, OSC port, and parameters

it’s based on the hello_video_cube example from Raspbian, so it uses the hardware decoding capabilities of the Pi

of course, it’s open source, feel free to test it : https://github.com/avilleret/rpi_osc_video_player

video player on Raspberry Pi

RPi sunning OpenELEC plugged in an old Sony Trinitron monitor
RPi running OpenELEC plugged in an old SONY Trinitron monitor

I made few tests with chnry on how to play movies with Raspberry Pi

we did the tests with a fresh Raspbian install and up-to-date
Raspbian comes with an integrated player dedicated to RPi : omxplayer
This uses hardware video decoding so it can play full HD h264 encoded film without lag.
The same is not possible with VLC (which only uses CPU decoding) we can’t find any codec which VLC can play smoothly but maybe it’s possible with a non CPU-expensive and small bandwidth codec.

Also we can heard some clicks on the analog output of the RPi when openning and closing omxplayer.
We guess this is due to the powering of the hardware but I think it could be handle on the software side.
For example, when Pd is sending some sound, and if we start playing a film with omxplayer we do hear clicks unless the sound card is powered.
Omxplayer seems to reset the sound card without regarding its state, so i think this is a bug.

So VLC is out on RPi, let’s try to control omxplayer over a network.
The simple way we find is using the udpreceive utility (which comes with puredata) and forwarding its output to bash.
On the RPi :
pdreceive 3434 udp | bash
and on the client :
echo omxplayer video.mp4 \& | pdsend 3434 192.168.11.11 udp

3434 is the port number
192.168.11.11 is the RPi’s IP
video.mp4 is the video we want to play (located in the RPi’s home)
\& go back to prompt just after starting omxplayer thus we can send other commands like killall omxplayer.bin to stop the player.

When no video is playing you will see either the command line or the LXDE interface.
With LXDE, you can set a black desktop, hide the menu bar and make the mouse disappear (with unclutter tool).

Next I will test how longer severals RPi can stay in sync and also I’ll take a look at XBMC with OpenELEC.

pix_freenect on Ubuntu 12.04

pix_freenect is one of the pd/Gem objects by Matthias Kronlachner to use Kinect sensor.
It’s not so simple to make it run on Ubuntu 12.04 64bit.
Here is a sum up of what I should do to make it work.
get the last libfreenect from git and make it (as the libfreenect package seems to not work with Matthias external) :
git clone https://github.com/OpenKinect/libfreenect.git
cd libfreenect
mkdir build
cd build
cmake ..
make
sudo make install

On my 64bit system, cmake puts the libs strangly in /usr/local/lib64 instead of /usr/local/lib. I moved all the files to /usr/local/lib, you can also make symbolic links.

I have to blacklist gspca modules to use the Kinect with freenect. I had a file named blacklist-gspca-kinect.conf in /etc/modprobe.d with that :
blacklist gspca_kinect
To prevent gspca module from loading on next reboot and to remove the module without rebooting :
sudo modprobe -r gspca_kinect

Now, get the latest pix_freenect code and make it :
git clone git://github.com/kronihias/pix_freenect.git
cd pix_freenect
mv Makefile Makefile_osx
mv Makefile_linux Makefile
make PD_DIR=/path/to/pd GEM_DIR=/path/to/Gem

You can also edit the Makefile and set the variables there. For me, the build failed because of unrecognized gcc arg : –export_dynamic. I edited the Linux LDLAGS variable on line 23 and replace by :
LDFLAGS = -shared -rdynamic
Make again and it should be ok. For now, pix_freenect can’t initialize when no Kinect is connected or if a wrong ID is set with arguments.