Raspberry PI APRS using Xastir

I had such great success with my Raspberry PI NAS that I decided to take a stab at running an APRS application with maps on a Raspberry PI. After searching the web I was not surprised to find that others have done something similar. Because I dedicated my original Raspberry PI as a NAS I obtained a second Raspberry PI model B along with some accessories from Adafruit Industries. Adafruit tests the accessories with the Raspberry PI so it eliminates the hunting for compatible accessories.

My intent for the APRS-PI was to read the APRS-IS and display those stations near my location.  My setup is:

• Raspberry PI Model B - Over clocked at 900 MHz
• Belkin 4 port powered USB hub
• SanDisk Cruzer Fit 16 GB USB Flash Drive for the file system 
• Class 10 SD Card
• WI-FI USB dongle 

Raspberry PI APRS

There are many websites that already exist for setting up a Raspberry PI NAS so I will not duplicate the steps here; however, these are some very helpful links.

• Setup SSH
• Move files system from the SD card to USB thumb drive
• Set up Xastir
• Set up the VNC server
• Updating Raspbian

The setup is fairly straight forward for Xastir on the Raspberry PI. Depending on what your intent is for using it the filter from the APRS database may need to be updated. I am using a filter of m/25 to retrieve stations within 25 miles of my location.

Xastir via VNC

A monitor could be added to the Raspberry PI via HDMI or the AV video output but while one of the 3.5" or 4.3" displays may sound good the resolution is too low to be able to fully use the Xastir. It can be done and the map with the stations can be viewed but the pop-up boxes for making changes are mostly larger than the small screen's real estate and the dialog boxes will be off the screen.

As always YMMV but for a small, low cost, always on APRS device the Raspberry PI fills the need.

Raspberry PI NAS

I have been excited about playing around with a Raspberry PI and I had some free time so I purchased a unit. I bought a Raspberry PI model B along with some accessories from Adafruit Industries. Adafruit tests the accessories with the Raspberry PI so it eliminates the hunting for compatible accessories.

My intent for the NAS was to create a low cost / low power device to store a backup of digital pictures. My setup is:

• Raspberry PI Model B - Over clocked at 900 MHz
• 7 port powered USB hub
• 2 Toshiba 1 TB USB drives
• SanDisk Cruzer Fit 16 GB USB Flash Drive for the file system 
• Class 10 SD Card

Raspberry PI NAS

There are many websites that already exist for setting up a Raspberry PI NAS so I will not duplicate the steps here; however, these are some very helpful links.

• Setup SSH
• Move files system from the SD card to USB thumb drive
• Setting up the USB drives and Samba
• Mounting the USB drives by UUID
• Formatting the USB drive as ext3
• Updating Raspbian

After combing through all of the information out on the web I first formatted the two USB drives as NTFS. This was so the drives could be easily plugged into a Windows (or Mac) should the Raspberry PI fail. After some initial tests I was not thrilled with the throughput writing to the USB drive. I did notice that the ntfs-3g driver was CPU intensive (~40%). After reformatting the USB drive as ext3 I reran the test at 900 MHz and was pleasantly surprised at the write time performance increase.

RPI w/ NTFS @ 900 MHz - 2.35 MB/s (18.8 Mb/s)

RPI w/ NTFS @ 900 MHz - 2.63 MB/s (21.04 Mb/s)

RPI w/ ext3    @ 900 MHz - 6.26 MB/s (50.08 Mb/s)

Due to the limitations of the USB bus on the Raspberry PI you will not see anything near the theoritical maximum throughput but I was more than happy to achieve 6.26 MB/s (50.08 Mb/s) throughput writing to the USB drive.

A cronjob can be used to rsync the contents of the first USB drive to the second drive (instructions in Setting up the USB drives and Samba). The second frive provides some added reliability for the data storage. You could also use a third USB drive and manually mount it, rsync, un0mount and store the drive in off-site or on-site fire / water safe storage.

To move the files from a Windows machine to the RPI NAS rsync for Windows can be used. Mac has rsync packaged with OSX which will make easier to copy data to the PI without the need for a third party application. 

As always YMMV but for a small, low cost, low power consumption NAS the Raspberry PI with two USB drives suits my backup needs.