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Datasheet: UDRCDS


Important: Use only Compass Linux images and dstarrepeater packages.  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

ircDDB Registration

If you are local simplex node or using a personal callsign, do not register at use QuadNet instead. If you want to use your personal call sign, you will be able to run the repeater and perform linking to repeaters and reflectors, but will be unable to do callsign routing including STARnet Digital groups.

Now is a good time to register a unique callsign for your repeater at  In the United States this needs to be a club callsign, in other countries a secondary callsign is necessary. If you already have an ircddbgateway registered, you can just add this repeater to it at configuration.

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 and will require hand editing of the dstarrepeater configuration file.  The full version has graphic configuration tools for those new to setting up dstarrepeater and ircddbgateway.
  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 via one of these methods
    1. Using the microUSB port next to the HDMI port (good if you are not at the repeater site)
    2. Through the 15-Pin connector while attached to the DR-1X repeater (Power down the repeater while installing the supplied 15-Pin cable)
  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.) 
    Note: DO NOT RUN raspi-update - it will break your install
  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™ 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

Starting dstarrepeater

Make sure the UDRC™ is connected to the radio or repeater via Mini-DIN 6 port.  

NOTE: Many standard Mini-DIN 6 cables, e.g. PS2 cables, do not have all of the pins wired and will not work!  Be sure your cable has all 6 pins wired straight through.  If you obtained the cable from NW Digital Radio it will have all pins wired.

Login to the Raspberry Pi and issue the command:

sudo systemctl start dstarrepeaterd@1
If you want to see a GUI, run the commands:
sudo systemctl stop dstarrepeaterd@1
sudo dstarrepeater 1

The UDRC should now decode D-STAR signals received on the radio or repeater's input. Test by keying up and watching the display on the D-STAR Radio.

Logs for troubleshooting are at /var/log/opendv

If you want the dstarrepeaterd daemon to start on reboot, issue the command:

sudo systemctl enabledstarrepeaterd@1

A video of hints for management of the daemon.


Each radio and repeater model may need adjustments to the standard configuration.  The items that may need adjustment are as follows:

  1. Under dstarrepeater config in modem sound card, make sure both TX and RX sound cards are set to udrc
  2. Also you may need to adjust TX and RX invert based on the radio and band.
  3. Modulation level is set using using the program alsamixer, select the udrc, adjust LO first and then PCM to get the right deviation
  4. Detection level is set in alsamixer with the ADC setting 

The "poor man's" approach to getting this working. (Without a deviation meter and spectrum analyzer.)

Use a second FM receiver and listen to the transmissions.  You should hear modem tones on each transmission, assuming you are using a simplex frequency (DUPLEX offset 0.0), for both your D-STAR radio and the radio or repeater.  Listen to the relative volume of the two transmissions.  Is the radio or repeater is 'louder' or 'quieter' than the D-STAR radio?  If it is louder then you need to decrease the drive of the modem out of the UDRC, if it's quieter, then you need to increase it.

If they are the same, then you need to adjust the TX polarity in modem setup (via dstarrepeaterconfig 1)

If the radio is keying but no tones, check the 'Sound Card' settings in dstarrepeaterconfig 1 -- make sure both TX and RX are set to udrc.

How do you change the drive level, you ask?  Glad you asked.

You need to open a terminal and run the program alsamixer and press 'F6' key to switch to the udrc.  See here for keyboard commands.

There are two controls that adjust the level of the modulation.  One titled PCM (on the far left) and one titled LO which is almost all the way to the far right (use the right arrow key to get to it). Start with the LO level, take it up or down (louder or quieter) to see if you get the output level right.  If that doesn't get you there, you may need to fine tune with PCM.  When you get it just right, look at the upper left of the screen and note the level in 'dB' for PCM and LO.  You can use those numbers to modify a script to reset the modem to those values in the future.

Note: if you do not hear any audio on the FM radio when the UDRC™ is transmitting, make sure LOL is not muted in alsamixer.

When you get it right, press the ESC key and give the command

sudo alsactl store
You can create your own script by saving the default script 

curl -L -s > ~/
chmod +x ~/
Edit the script changing the values for PCM, LO, and ADC according to what you found in alsamixer setup.

You can then use the script to reset values when needed.


Since there are no special instructions for ircDDBGateway for the UDRC™, please refer to the documentation in the files section of the Yahoo Group  ircDDBGateway  If you would like a web based dashboard for ircDDBGateway, check out the real time dashboard at  ircNodeDashboard

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.