How to make the Raspberry Pi automatically restart the WiFi interface

My WiFi router sometimes goes haywire and the Pi won’t notice when the WiFi connection is up again. So I wrote this little script:



ping -c4 ${TESTIP} > /dev/null

if [ $? != 0 ]
logger -t $0 "WiFi seems down, restarting"
ifdown --force wlan0
ifup wlan0
logger -t $0 "WiFi seems up."

You can put this script under /usr/local/bin and add the following line to the system wide /etc/crontab:

*/5 * * * * root /usr/local/bin/

This will check every five minutes if the connection is still up, and restart it, if the router cannot be pinged. If you dislike all the syslog messages, you can comment them out in the script.
My corresponding /etc/network/interfaces looks like this (I uninstalled all the network managers):

auto lo

iface lo inet loopback
iface eth0 inet static

auto wlan0
iface wlan0 inet dhcp
pre-up wpa_supplicant -Dwext -i wlan0 -c /etc/wpa_supplicant/wpa_supplicant.conf -B
post-down killall wpa_supplicant ; rmmod 8192cu ; modprobe 8192cu

iface default inet dhcp

The wpa_supplicant.conf should be easy to generate, there are lots of guides on the web for this.

Attaching a USB sound card to the Raspberry Pi

Since my Raspberry Pi runs headless, and the analog audio output is not that great, I decided to add a USB sound card to my little machine. I took a Roland UA-1G, which I was using before on an OpenWRT machine. The device was immediately recognized:

Bus 001 Device 007: ID 0582:00ea Roland Corp.

However, ALSA will prohibit the card from becoming sound device #0, thus being the default. For that you have to comment out the following line in /etc/modprobe.d/alsa-base.conf:

# Keep snd-usb-audio from beeing loaded as first soundcard
#options snd-usb-audio index=-2

After rebooting or restarting ALSA, the Roland will become the default sound device:

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: UA1G [UA-1G], device 0: USB Audio [USB Audio]
Subdevices: 0/1
Subdevice #0: subdevice #0
card 1: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
Subdevices: 7/8
Subdevice #0: subdevice #0
Subdevice #1: subdevice #1
Subdevice #2: subdevice #2
Subdevice #3: subdevice #3
Subdevice #4: subdevice #4
Subdevice #5: subdevice #5
Subdevice #6: subdevice #6
Subdevice #7: subdevice #7

Playing with REST: SilverShield USB power web frontend

Yesterday I started to code a small tool that lets me turn on and off power outlets on my USB controlled  power strip. You can find the humble beginnings over at github. It uses the sispmctl tool to turn on and off the sockets. It is implemented in Python using the Tornado web server. The rendering is simple, not styled and not yet HTML compliant. But it already scans for attached devices, and lets you toggle single outlets. However, today the power strip sort of died on me, and now I have to look for another project to practice REST with…

How to turn the Raspberry Pi into a music server

I have set up my Raspberry Pi as a music and file server. My requirements were:

  • Big local storage (HD), shared over WiFi
  • Local music playing capability, remotely controllable
  • AirPlay speaker capability
The means by which I fulfilled the requirements were:
  • Platinum 1TB MyDrive and Edimax EW-7711UTn USB wireless adapter
  • mpd Music Player Daemon
  • shairport AirPort emulator
For the first part, I bought a WiFi adapter, the Edimax EW-7711UTn. This one works out of the box with Raspbian, using WPA encryption (Note: I switched to a RTL8188 based dongle by now). It identifies itself with lsusb as:
Bus 001 Device 004: ID 7392:7711 Edimax Technology Co., Ltd EW-7711UTn nLite Wireless Adapter [Ralink RT2870]
This can be easily configured using the wpa_gui tool that comes with the default Raspbian installation. Settings will be saved and restored upon reboot.
Second, I installed samba, samba-common and samba-common-bin for sharing my USB drive. The latter one is a Platinum MyDrive, which is attached to a powered Belkin 7-port USB hub, so that I only need two power supplies. One for the Raspberry Py, and one for the Hub and its attached devices. The MyDrive has been formatted with NTFS, so as to be easily mountable under Linux, OS X and Windows. I mount it using the standard /etc/fstab mechanism. Just added one line to the file:
/dev/sda1       /media/MyDrive  ntfs-3g defaults          0       0
The /etc/samba/smb.conf gets in its first iteration only one additional share, a write-for-all public share, as a big file dump: 
    comment = Free for all
    read only = no
    path = /media/MyDrive/FreeForAll
    guest ok = yes
Note that literally everybody in your LAN can access this and write to it! You may want to fine tune this…
Now to the mpd. It is easily installed by doing apt-get install mpd. When configuring it via /etc/mpd.conf make sure to change the following lines:
music_directory         “/media/MyDrive/Music/”
password                “MyVeryOwnPassword@read,add,control,admin”
bind_to_address         “any”

Change the directory and password to your liking. Then restart the service or reboot you device. You can control the mpd using a magnitude of clients. For example Theremin for OS X or Mpod for iOS.
Finally, I would like to be able to use the RasPi as an AirPlay target for my Mac and my iOS devices. This can be done via shairport. There are already a lot of good howtos for shairport on the Raspberry Pi. So I refer you to one of those. Two things come to my mind, though:
  1. The Net::SDP library, required by shairport, is not available on Raspbian by default. It is best to clone the github mirror, and go by its installation instructions. Installation via CPAN fails, plus CPAN needs huge amounts of RAM.
  2. The configuration needs to be tweaked a bit. The /etc/init.d/shairport script should be tuned to a sensible name for your RasPi. 
This way, you will be able to see the RasPi in your AirPlay speakers list and it will be happily churning along.