Enabling the watchdog timer on the Raspberry Pi

Turns out that the Broadcom BCM2708 chip on the RPi has a hardware watchdog. This can be very useful if your RPi is located remotely and locks up. However, this would not the preferred method of restarting the unit and in extreme cases this can result in file-system damage that could prevent the RPi from booting. If this occurs regularly you better find the root cause of the problem rather than fight the symptoms. Enable Watchdog Kernel Module echo 'bcm2708_wdog' >> /etc/modules sudo modprobe bcm2708_wdog Install Watchdog Daemon sudo apt-get install watchdog chkconfig chkconfig watchdog on sudo /etc/init.d/watchdog start sudo vim /etc/watchdog.conf # Uncomment the line watchdog-device = /dev/watchdog # You might also want to uncomment max-load-1, or add something like "max-load-1 = 24" to reset your Pi if the load average exceeds 24 in any 1-minute span. sudo /etc/init.d/watchdog restart The watchdog daemon will send /dev/watchdog a heartbeat every 10 seconds. If /dev/watchdog does not receive this signal it will brute-force restart your Raspberry Pi. If you are feeling adventurous you can test the setup by launching one of the fork-bombs you can find out there. Just make sure you don't have anything of importance running. : (){ :|:& };: Thanks to gadgetoid for the original tip !

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Dropping the wires on the Raspberry PI

Testing the RPi for some remote sensing application I needed to use a wireless connection as it would have been a pain to reach with an Ethernet cable. Parts Raspberry Pi Series B 512MB Raspbian 3.6.11+ Kernel Comfast 802.11n - Realtek RTL8188CUS WLAN Adapter Install WPA Supplicant sudo apt-get install wpasupplicant See http://en.wikipedia.org/wiki/Wpa_supplicant Check for the USB adapter sudo lsusb This should show output similar to this (depending on your USB adapter) Bus 001 Device 004: ID 0bda:8176 Realtek SemicondRTL8188CUSuctor Corp. 802.11n WL:AN Adapter Generate PSK Key If you want to use the cleartext PSK you could probably skip this step. wpa_passphrase YOUR_SSID YOURCLEARTEXTWPAKEY This should show output similar to this: network={ ssid="YOUR_SSID" #psk="YOURCLEARTEXTWPAKEY" psk=c885c4288a0c68b989289586cb075c0ccd1729d2c035820d02ed813fc729f317 } Edit network configuration sudo vim /etc/network/interfaces auto wlan0 allow-hotplug wlan0 iface wlan0 inet dhcp wpa-ssid "YOUR_SSID" wpa-psk c885c4288a0c68b989289586cb075c0ccd1729d2c035820d02ed813fc729f317 Finish off sudo shutdown -h now Unplug ethernet cable Power up the RPi and you should see another wireless DHCP assignment on the router

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Webserver and database combination on Raspberry Pi

My normal combination on the big-server side would be Apache + MySQL (or PostgreSQL), but on the RPi this seems to be absolute overkill. For data-logging operations I would not use the local system anyway (looking at MQTT as well as Remote MongoDB datastore via REST Webservices). After some poking around and reading up on the options I decided to go for the following combo: LightHTTPD + SQLite. Both are lightweight replacement of their fully-featured big-server counterparts (Apache HTTP & MySQL) and have very familiar configurations. There would be other options that have even less resource usage, but I really don't have the time to start from scratch somewhere. Another reason to go for this combination is that these are very well supported systems with regular security audits. Even though I am not planning to use my RPi's for anything mission-critical this is always worth a consideration as you don't need to unnecessarily introduce vulnerabilities to your network. Install & configure LightHTTPD sudo apt-get install lighttpd php5 php5-cgi php5-sqlite sudo lighty-enable-mod fastcgi sudo lighty-enable-mod fastcgi-php Further config changes can be also made via the config file. sudo vim /etc/lighttpd/lighttpd.conf sudo service lighttpd force-reload Install & configure SQLite sudo apt-get install sqlite3 sqlite3 /home/username/database_name.db All other commands are standard SQL from the 'sqlite>' command prompt or via SQL scripts like sqlite3 /home/username/database_name.db < sql_script.sql Access Databases from the webserver (using PHP) < ?php $db = new SQLite3('mysqlitedb.db'); $results = $db->query('SELECT bar FROM foo'); while ($row = $results->fetchArray()) { var_dump($row); } ?>…

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Chromebook tips to get started

Just got myself (actually it's for our Office Manager back in OZ) one of these Chromebooks while in Europe (since Google Australia with their absolutely hopeless hardware strategy do not seem to be able to ship any devices - Nexus 4 anyone ?) . Since the first days turned out to be a bit of a frustrating experience, I thought I share some of the findings as I had a hard time finding much useful info on troubleshooting ChromeOS. Wireless Connection (WIFI) Do not use WPA (or for that matter WEP) connections with ChromeOS. I had extreme difficulties browsing webpages on the Chrombook. Some pages would load, some pages would not load at all. There seemed to be no consitency to it as some would load one day, but not another. Somewhere in the Google Groups there seemed to be people reporting issues with wireless connections using WEP. It turned out that the Wireless Modem Router (Telekom Austria supplied Pirelli PBS modem) where I was staying was set to WPA encryption only by default. Once I figured out how to set the unit to WPA2 (which these days should really be the default anyway) things started to actually work consistently. Check the sections below (specially chrome://diagnostics) to see how you can find out what's going wrong. However to save some trouble & frustrations, before you do anything make sure your Chrombook connects using WPA2 ! Terminal CTRL+ALT+T will launch the Chrome Shell which is a slightly odd and very cut-down…

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Raspberry Pi – Raspbian post install tasks

The Raspbian Install process is fairly well documented using the Raspbian Installer. This is just to document common tasks after the stock install. Install base utils apt-get install sudo vim ntpdate git-core binutils make gcc ca-certificates rpi-update Allow non-root user account access to 'sudo' adduser USERNAME sudo For those Ubuntu users there is no 'admin' group in Raspbian (Debian Wheezy). NTP time update sudo rm /etc/localtime sudo ln -s /usr/share/zoneinfo/Australia/Adelaide /etc/localtime sudo ntpdate -u au.pool.ntp.org Probably best to choose an NTP Server closest to your location or provided by your ISP Firmware upgrade EDIT (2014-03-31): rpi-update is now part of the Raspbian repositories and can be installed via apt-get install rpi-update (I have added this to the above line). Note: unless you want the latest firmware this is not a necessary step as apt-get will update the firmware to the latest stable release. Using Hexxeh updater. Install dependencies wget http://goo.gl/1BOfJ -O /usr/bin/rpi-update && sudo chmod +x /usr/bin/rpi-update sudo rpi-update Install WiringPi Thanks to the excellent work of Gordon Henderson (https://projects.drogon.net/raspberry-pi/wiringpi/) this is a C-based program to read/write to the Raspberry Pi GPIO pins. cd /usr/share git clone git://git.drogon.net/wiringPi cd wiringPi git pull origin ./build Output: wiringPi Build script ===================== The wiringPi I2C helper libraries will not be built. WiringPi library [UnInstall] [Compile] wiringPi.c [Compile] wiringPiFace.c [Compile] wiringSerial.c [Compile] wiringShift.c [Compile] gertboard.c [Compile] piNes.c [Compile] lcd.c [Compile] piHiPri.c [Compile] piThread.c [Compile] wiringPiSPI.c [Compile] softPwm.c [Compile] softServo.c [Compile] softTone.c [Link (Dynamic)] [Install] GPIO Utility [Compile] gpio.c [Link] [Install] All Done. Testing the…

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Mongodb / Python development install on Ubuntu

Add apt repository key sudo apt-key adv --keyserver keyserver.ubuntu.com --recv 7F0CEB10 Add apt repository sudo vim /etc/apt/sources.list.d/10gen.list #add the following line: deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen Install mongodb & python utils sudo apt-get update sudo apt-get install mongodb-10gen python-pip python-dev build-essential pip install pymongo

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Accessing 1-wire devices on Raspberry Pi using OWFS

To connect 1-wire serial devices to the RPi I am using a DS9490R USB 1-wire adapter (rather than wiring I2C 1-Wire master components to GPIO I2C - which I might look at sometime down the track) Install packages sudo apt-get install owfs ow-shell Edit config file vim /etc/owfs.conf ! server: server = localhost:4304 # USB device: DS9490 server: usb = all ######################### OWFS ########################## mountpoint = /mnt/1wire allow_other ####################### OWHTTPD ######################### http: port = 2121 ####################### OWFTPD ########################## ftp: port = 2120 ####################### OWSERVER ######################## server: port = localhost:4304 Create Startup Script I created a startup script for owfs modelled on the owserver script (not sure why this one is actually missing) vim /etc/init.d/owfs #!/bin/sh ### BEGIN INIT INFO # Provides: owfs # Required-Start: $remote_fs $syslog $network $named # Required-Stop: $remote_fs $syslog $network $named # Should-Start: owfs # Should-Stop: owfs # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6 # Short-Description: 1-wire file system mount & update daemon # Description: Start and stop 1-wire file system mount & update daemon. ### END INIT INFO CONFFILE=/etc/owfs.conf DESC="1-Wire file system mount" NAME="owfs" DAEMON=/usr/bin/$NAME case "$1" in start) echo "Starting $NAME" $DAEMON -c $CONFFILE ;; stop) echo "Stopping $NAME" killall $NAME ;; *) echo "Usage: $N {start|stop}" >&2 exit 1 ;; esac exit 0 Starting daemons /etc/init.d/owserver start /etc/init.d/owfs start Checking output #ls /mnt/1wire/ Should show output similar to: 10.575349000000 12.95DD17000000 alarm simultaneous uncached 10.575349000000 12.95DD17000000 bus.0 statistics 12.57DD16000000 81.B2EA2E000000 bus.1 structure 12.57DD16000000 81.B2EA2E000000 settings system cat /mnt/1wire/10.575349000000/temperature Will then show…

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Installing OMXPlayer on Raspberry Pi

Since I didn't have any luck playing videos on the RPi using mplayer I found omxplayer after some search. It has the ability to use the RPi's GPU thus taking some load of the CPU. UPDATE 2013-04-01: omxplayer is now included in the Raspbian (Debian Wheezy) repositories and can be simply installed by one line. sudo apt-get install omxplayer Check another article on how to install Raspbian. OMXPlayer binary (.deb) downloads can be found here: http://omxplayer.sconde.net/ Install dependencies apt-get install libpcre3 fonts-freefont-ttf fbset libpcre3-dev libpcrecpp0 libva-dev libva-x11-1 libva1 Install omxplayer wget http://omxplayer.sconde.net/builds/omxplayer_0.2.4~git20121205~ec7ac68f_armhf.deb dpkg -i omxplayer_0.2.4~git20121205~ec7ac68f_armhf.deb Play video omxplayer -o hdmi video.mp4 Note: If there is no sound when playing through the HDMI interface make sure your /boot/config.txt file has the following line (and it's not commented out). hdmi_drive = 2 OMXPlayer Key bindings Key Action 1 Increase Speed 2 Decrease Speed j Previous Audio stream k Next Audio stream i Previous Chapter o Next Chapter n Previous Subtitle stream m Next Subtitle stream s Toggle subtitles q Exit OMXPlayer Space or p Pause/Resume - Decrease Volume + Increase Volume Left Seek -30 Right Seek +30 Down Seek -600 Up Seek +600

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Raspberry Pi – Text to Speech

Just a quick note on Speech Synthesis a Raspberry Pi project. I had to research some of the options on the Raspberry Pi while looking into a project where I need some audio announcements. Configuring Sound echo 'snd-bcm2835' >> /etc/modules sudo modprobe snd-bcm2835 sudo apt-get install mplayer alsa-base alsa-utils pulseaudio mpg123 # make mplayer use mpg123 codec instead of default ffmp3float echo "afm=mp3lib" >> ~/.mplayer/config Since I am using Raspbian which is a Debian based (Wheezy) Distribution I used some Ubuntu documentation (https://help.ubuntu.com/community/TextToSpeech) as the starting point. Festival sudo apt-get install festival festival-english echo "Hello World - Testing" | festival --tts Plus: Local install (no internet connection required) Minus: Mechanical sounding voice Espeak sudo apt-get install espeak espeak -v en "Hello World - Testing" Plus: Local install (no internet connection required) Minus: Mechanical sounding voice (slightly better than Festival) Google Translate Create a shell script tts.sh #!/bin/bash mplayer -ao alsa -noconsolecontrols "http://translate.google.com/translate_tts?tl=en&q=$*" > /dev/null 2>&1 chmot +x tts.sh ./tts.sh "Hello World - Testing" Plus: needs live internet connection Minus: excellent human sounding voice Google Speech API I will most likely look at this in the long run to get better control rather than calling the Google Translate url too much.

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