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Datasheet: UDRCDS


Important: Use only Compass Linux images.  They contain support specific to the UDRC™. Source is available for review on GitHub.

Mount your UDRC™ on a Raspberry Pi 2 or 3

Make sure the pins are properly aligned and use the supplied standoffs to support the board above the HDMI port.

Universal Digital Radio ControllerUniversal Digital Radio Controller

Create the Boot Image

  1. Obtain a high quality microSD card.  A Class-10 card of 8GB or more is recommended.
  2. Download a Compass Linux image from
  3. The 'lite' version is without a GUI.  The full version has graphic interface and is recommended if you plan to have a GUI application running.
  4. Unzip and copy the uncompressed image to the SD card using the procedure outlined on the Raspberry Pi site.

Boot for the First Time

  1. Place the microSD card in the Raspberry Pi.
  2. Attach a monitor and keyboard/mouse to the Raspberry Pi
  3. Attach Ethernet via the RJ-45 jack to your network.
  4. Apply power 
    1. Using the micro USB port next to the HDMI port 
    2. There are solder pads to apply 12 vdc to the UDRC if that is more convenient 
  5. Allow the Raspberry Pi to boot up
  6. Login  (User: pi, Password: raspberry)
  7. From a terminal command line, verify that the UDRC™ is recognized by typing the command aplay -l (that's a lowercase l) and observe that udrc is listed as a card.  If you do not see it listed, power down and remount the UDRC™.
  8. Perform any Linux configuration specific to your installation, e.g. assign specific network addresses, install favorite tools, etc. (This is beyond the scope of NW Digital Radio support, please use Linux support resources for assistance.)
  9. You may wish to edit the /etc/hosts file and add reference to the hostname, for example if you keep the default 'compass' hostname, add a line    compass
  10. To preset the pins and levels on the UDRC™ for direwolf we provide a script.  Execute the following
    curl -L -s | sudo sh
    (the 'pipe' or | is usually above the \ key on most keyboards -- if you want to see what the script does, leave off  '| sudo sh')
  11. To gracefully shutdown the Raspberry Pi, you may use the command sudo halt

Build and Install Direwolf

apt-get install libasound2-dev
cd ~
git clone
cd direwolf
sudo make install
make install-conf

Configure Direwolf

Read the README

Download the User's Guide

Peruse other documents on the WB2OSZ Github for ideas and troubleshooting -- however, you do not need to perform the items in Raspberry Pi document. The UDRC only needs a few edits in direwolf.conf 

cd ~

Use your favorite editor, e.g. nano or vi to edit file direwolf.conf 

vi direwolf.conf
# or
nano direwolf.conf

Follow the directions in the file for setting up MYCALL, PBEACON, DIGIPEATER, and IGSERVER/IGLOGIN

Set the following parameters

ADEVICE plughw:CARD=udrc,DEV=0

Under CHANNEL 0 -- Choose MODEM (1200 and 9600 for VHF/UHF) and set the PTT


If you are using 9600 (Discriminator Audio), also setup CHANNEL 1 with

MODEM 9600

Attach Radio and Start Direwolf

Use the Mini Din-6 connector to attach a radio with a 9600 baud packet port.  Many radios have a Mini Din-6 socket specifically for this purpose, use a straight through male to male Mini Din-6 cable.  If you selected Mini Din-6 when ordering the UDRC, use that cable.  If you need a specialized cable to go to another radio, you can build one or see Cable and Connectors on the NW Digital Radio blog.

Startup direwolf

cd ~


The values set by the script should be sufficient, but controls exist in the alsamixer program to adjust PCM (modulation for TX) and ADC (receive), after selecting the UDRC as the sound device.  Use them judiciously and save changes with the command

sudo alsactl store

You may wish to save the initial script and change the db values you pick in alsamixer.  

cd ~
curl -L -s  >
chmod +x
Use your favorite editor to modify the new shell script.  You can execute it any time



Many applications can be used with direwolf 

One quick application is Xastir for APRS.

apt-get install xastir

Support Group

NW Digital Radio is in the process of setting up various community groups at Please create a personal account at Join the main NW Digital group by sending an email from your registered email account to and then send an email to Please use the group for questions and to share your experiences, so that all UDRC™ users can benefit from the replies.

Please share your solutions at