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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.

During initial startup do not modify the basic Raspberry Pi setup. For example, do not overclock the Raspberry Pi, it is not needed as performance is more than adequate, and doing so can change clocking values on busses used by the UDRC™ causing it to either not function or be unstable.  If you make any changes not listed in these instructions, and your UDRC™ does not function, return to the original settings.

Mount your UDRC™ on a Raspberry Pi 2 or Pi 3

Note: Raspberry Pi 3 Addendum

ARMv6 Raspberry Pis are not supported. This includes the A/A+, Zero, Pi 1 B/B+, and Compute Module.

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

Universal Digital Radio Controller
Universal Digital Radio Controller

ircDDB Registration

If you are a local simplex node or using a personal callsign, do not register at use QuadNet 2 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.

If you are running a repeater, and haven't previously registered at ircDDB, now is a good time to register a unique callsign for your repeater at ircDDB.netIn 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.

Install Compass Linux


Basic Configuration

  1. 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™.
  2. To preset the pins and levels on the UDRC™ we provide a script. Execute the following:
    cd ~
    curl -L -s >
    chmod +x
    sudo ~/
  3. Optionally disable the internal sound chip by editing /boot/config.txt and commenting out this line (recommended unless you need it for something else):

Install Applications

You may install any mix of GUI and non-GUI versions of the repeater and gateway software. Use the following commands on the command line.

GUI Version

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install dstarrepeater ircddbgateway dstarrepeaterd ircddbgatewayd

We install the daemon versions as well because once you have everything configured you would typically run headless.

If you want a set of desktop Icons to start the GUI applications, see:

and download file icons.tgz to the 'pi' user home directory /home/pi then

tar -xzvf icons.tgz

Non-GUI Version

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install dstarrepeaterd ircddbgatewayd

If you are running ircddbgateway on another computer, there is no need to install it on the Pi. You will configure dstarrepeater to access the ircddbgateway.

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

Download the Seed File for dstarrepeater

sudo curl -L -s -o /etc/opendv/dstarrepeater_1

Edit Using GUI

sudo -E dstarrepeaterconfig 1

Edit on Non-GUI System

This requires extensive knowledge of the key/value pairs used in configuration and is not recommended for those new to dstarrepeater configuration.

sudo nano /etc/opendv/dstarrepeater_1

You will need to change the repeater callsign and gateway callsign to your system. If you are doing a 70cm repeater these are the only settings that need changed for initial configuration. Only adjust other settings if you understand their effect.

In /etc/opendv/dstarrepeater_1 set:

# For simplex access points (hotspots) and non DR-1X repeaters attached to the Mini DIN-6 connector

Set mode for simplex

or duplex

Start Up

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.

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

sudo systemctl enable dstarrepeaterd@1

A video of hints for management of the daemon.


NW Digital Radio does not possess, or test, every model of radio or repeater that may be used in homebrew hotspots and repeaters. You will need to use this troubleshooting guide to determine the right settings for your particular install.

Logs for troubleshooting are at /var/log/opendv

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 fo 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 -o ~/
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.


Visit our quick startup Wiki page for ircDDBGateway .

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