Raspberry Pi

I placed a  Raspberry Pi (RPI) order to RS Components  in early March and this credit card sized  $35  Linux computer finally arrived on Monday.  

  
After quick visual inspection everything looked OK so I inserted the SD card into socket, connected HDMI cable to my display, keyboard cable to USB socket and plugged a  Nokia USB cellphone charger to power up this latest toy.  A familiar Linux bootup screen appeared and  after entering the default username "pi"  and password "raspberry"  I was logged in.

CONFIGURING RASPBERRY PI IN HEADLESS MODE 

One of the first objectives was to configure RPI in headless mode. I wanted to have access to this tiny computer via SSH and VNC remotely over the network.   Enabling SSH is as simple as renaming the "boot_enable_ssh.rc" to "boot.rc" in the /boot directory.  You can do this even before powering up with SD card mounted on another computer and just renaming the file. 


I connected LAN cable from my router and checked that I had proper IP address via  /sbin/ifconfig  command.  I used the following steps to get VNC working: 

sudo apt-get install tightvncserver       -  to install VNC server
tightvncserver                            -  to set a password
sudo vi /etc/init.d/vnc                   -  to create a startup script
sudo chmod +x /etc/init.d/vnc             -  to make the script runnable
sudo /usr/sbin/update-rc.d vnc defaults   -  to install the script for boot

The vnc script itself is below:

#! /bin/sh
# /etc/init.d/vnc


USER=pi
HOME=/home/pi
export USER HOME
case "$1" in
    start)
        echo "Starting VNC Server"
        #Insert your favoured settings for a VNC session
        su - $USER -c "/usr/bin/vncserver :1 -geometry 1024x768 -depth 16 > /tmp/vncserver.log 2>&1 &" &
    ;;
    stop)
        echo "Stopping VNC Server"
        /usr/bin/vncserver -kill :1
    ;;
    *)
        echo "Usage: /etc/init.d/vnc {start|stop}"
        exit 1
    ;;
esac
exit 0

VNC server can now be started with


/etc/init.d/vnc start 


On my Mac  I used Chicken of the VNC to connect to RPI.  In my particular network the configuration is the following (RPI is on 192.168.1.2 port 5901) :

After these steps  I am able to connect both via SSH command line and VNC  to this Rasperry Pi box. See screenshot below.  

The screenshot also shows some additional ham radio software that I have already installed such as FLDIGI and  Xastir. 

With wireless USB Wifi card installed (I used D-Link DWA-140 that I had available from other projets) RPI becomes quite portable within the range of Wifi access point.  I used  as  wicd  network manager to configure wireless USB Wifi card.  

PROJECT IDEAS HOW TO USE RASPBERRY PI 

RPI does have built-in audio output but no microphone or line input.  Therefore you need to get a USB audio device to connect it to a radio. I did not have one available right now but wanted to test how FLDIGI would work.  I installed FLDIGI  using this command

sudo apt-get install fldigi 

and followed these steps to configure ALSA audio.  After starting FLDIGI and going through configuration screens I got it running and tested sending some Morse code.  Clear audio came out from the headset plugged in.   Some other hams have also tested FLDIGI with USB audio devices with positive results.  FLDIGI does consume some 80% of CPU when sending - but I have not done any optimizations, just downloaded normal FLDIGI distribution from Debian repositories. 

I also installed Xastir  to test how APRS tracking would work on Raspberry PI.  Installation is as simple as: 

sudo apt-get install xastir 

I did play some time with Xastir and downloaded some maps but the SD memory card was getting quite full so I decided to postpone these tests until I had a larger SD card available.  Anyways, Xastir started without hickups  and I was able to see Massachusetts maps and lookup stations.  I ended up removing Xastir  to make some space. 

I also tested the built-in Midori web browser - it is not the fastest browser on the planet but did a pretty good job bringing up  http://aprs.fi  created by Hessu OH7LZB.  See screenshot example below 

I also installed nginx webserver using the instruction over here. 




Based on this very cursory testing Raspberry Pi seems to  run existing ham radio software quite well  (given CPU capacity restrictions).  I am envisioning that Raspberry Pi  could be used for many different kind of Ham Radio projects, such as 

• Use Xastir and connect RPI to 2m/70cm hand held radio to provide a simple APRS tactical  display for event organizers, like Boston Marathon 
• Portable beacon station that can also send telemetry information such as weather, location, even pictures from USB webcams, etc. 
• Use a simple Softrock type USB card and SDR software to create ultraportable Software Defined Radio
• Remote control system of ham radio station over the Internet
• Portable APRS digipeater   

I am positively surprised how capable this tiny $35  Linux computer actually is.   It certainly exceeded my expectations. 

73 

Mauri  AG1LE