1. Introduction
  2. My OpenGD77 Code Plug [Download Here]
  3. Marine and Citizen Bands
  4. Radioddity GD77 Key Names and Functions
  5. User Guide
  6. Downloading the Firmware, Source and Associated Tools
  7. udev rules for Ubuntu
  8. The Linux firmware Loader
  9. Starting the GD77 in CPS Update Mode or Firmware Update Mode
  10. Installing the Firmware
  11. The Programming Cable
  12. Community CPS or OpenGD77 CPS
  13. Building a New Code Plug
  14. The GB3GF cvs utility
  15. Programming Hints
  16. Frequency Bands
  17. References

Related Pages:
  1. Any-Tone-AT-D868
  2. RB-STM32-DVM
  3. Equipment/MMDVM_HS_Dual_Hat_Duplex/MMDVM_HS_Dual_Hat_Duplex.html
  4. Mutli-Mode-Digital-Voice-Modem
  5. Pi-Star
  6. DMR



OpenGD77 is an open source (GNU General Public Licence Version 2) and is a great effort on the part of Rodger Clark, VK3KYY, in Melbourne and his co-authors. Rodger Clark is a Freelance IT Consultant & Developer, based in Melbourne Australia and is a legend in DMR firmware, modifications, and the DMR mode. It is the opinion of man that this firmware is far superior to the manufactures. I am certaintly, of that opinion. He is to be congratulated.

Rodger's web site is here:

The User Forum is here: It is the opinion of many that this firmware is far superior to the manufactures firmware.

The github repository is here:


My OpenGD77 Code Plug [Download Here]

This is the code plug I use with the Open GD77 Firmware:

[Download link to 2020-08-19-No-ID.g77]

Note the Callsign is blank and the DMR ID is a nonsence as the OpenGD77 CPS will not allow it to be blank.


Marine and Citizen Bands

The Codeplug comes with marine VHF and CB UHF frequencies. As we know, the marine and citizen band channels are outside the amateur radio bands As a resukt they are enabled to receive only. If you try to tramsmit on these frequencies you will get an error message: ERROR - Out of Band

To enable out of band transmitting do the following:

Note The use of the VHF Marine Bands requires operators to hold a minimium of a SHORT RANGE OPERATOR CERTIFICATE OF PROFICIENCY (SROCP)

Australian Maratine College's SROCP:

Note thes are software controlled band limits, and this is a separate issue to the hardware band constraints. The RF hardware can't technically operate reliably outside these bands.


Radioddity GD77 Key Names and Functions

This diagram is usefull. I printed this out in colour and keep it with my radio.

Note that, the OpenGD77 community and documentation often refer to the SK and TK keys, other times to the Black, Blue, Orange, and Green and Red keys. This table may help decipher the instructions.

Button Position Colour Short press Long press
SK1 1st one under the PTT Black Menu Nothing programmed yet
SK2 2nd one under the PTT Blue Channel info Channel info
TK Top button next to antenna Orange High/low power select Long press = Scan On/off
Menu Left-hand button under the screen Green Menu
Exit Right-hand button under the screen Red Exit or Back


User Guide

NOTE: This User Guide is the version extracted from the source archive on the github repsoitory.
Please check for up to date versions.

User Guide as at August 2020 (R2020.06.27): docs/OpenGD77_User_Guide.pdf


Downloading the Firmware, Source and Associated Tools

The most current stable release can be obtained from this github repository.

The github Download:

At time of writing these files were available for download.
  1. FirmwareLoader.exe
  3. OpenDM1801.sgl
  4. OpenGD77.sgl
  5. OpenGD77S.sgl
  6. OpenGD77_User_Guide.pdf
  7. Source code(zip)
  8. Source code(tar.gz)

On Windows download FirmwareLoader.exe.

On Linux download the firmware loader,, that runs on the Ubuntu. Be sure to extract and update the udev rules.

On both platforms, the firmware file, OpenGD77.sgl, is required.

I downloaded the User Guide, OpenGD77_User_Guide.pdf, but found it failed to navigate or link correctly, so I then downloaded the Source file, Source code(zip) that linked to and extracted the User Guide, OpenGD77_User_Guide.html and the OpenGD77 Quick Guide Graphic.jpg.

Be sure to check the github repository for more current versions. This is current as at August 2020.


udev rules for Ubuntu

udev rules 99-gd77.rules:

The file can be found in the master github archive at "OpenGD77-master/Linux/etc/udev/rules.d/Ubuntu"


The Linux firmware Loader


Starting the GD77 in CPS Update Mode or Firmware Update Mode

CPS Update Mode: To read and write the code plug (configuration) data turn your radio off, then connect it to your PC via the cable, and then turn the radio on. No button are required to be held down.

Firmware Update Mode: To allow the firmware to be updated, turn your radio off, then connect it to your PC via the cable, then hold down the two buttons, black and blue ones, below the PTT button on the left hand side, and then turn the radio on. The radio screen will be black with the green light on only, which means the radio is in firmware upgrade mode.


Installing the Firmware

On linux: run "mono firmware-loader.exe". See The Linux firmware Loader above.

On Windoze: The easiest way is to install the OpenGD77 Code plug application and Select "Extras" option and then select the "Firmware loader" option.

The firmware loader will display the following the screens:


I selected the Stable Version:


If the cable or Driver is not correct this Error is displayed:



The Programming Cable

The programming cable contains no electronics and is simply a wired connection, so it is possible to manufacture one in the shack. The radio contains the communication hardware and is a FREESCALE SEMICONDUCTOR INC. USB COMPOSITE DEVICE. The hardware descriptor is: idVendor=15a2, idProduct=0073, bcdDevice= 0.02.

This is a USB HID, human interface device class and a USB Composite Device. A Composite Device as the name suggests, is a peripheral device that supports more than one device class in the one physical USB port.

See: for more details.

It is loaded as a Abstract Control Model (ACM) USB Devices or often called a "Virtual Comm Port".

See: for more details.



The linux system log before the Open Firmware load:

The Linux system log before the Open Firmware load performed on Windows 10::

I do not understand why this changed after I loaded the OpenGD77 firmware. Maybe the firmware updates the devices firmware in the phone. Maybe this is the resolved by loading the udev rules.


Community CPS or OpenGD77 CPS

The OpenGD77 Code Plug Software will not run under Linux at present, although a Linux version is foreshadowed. So it is time to move to the Windoze platform. I am running Windows 10. Download the OpenGD77 application here:


Building a New Code Plug

I started with this code plug from VK3TBS:

Even though it was written in 2019 it was the best I could find and a good starting point for VK4-land. I then exported the code plug to csv files with the GB3GF utility. I then loaded these into open Office where I could edit these with all the power of a spreadsheet. However, I consistantly got errors when attempting to reload these into the CPS application.


So, make sure that all programs are closed that are accessing the csv files or the load will crash. No harm but you will have to start again.


The GB3GF cvs utility

Exporting to csv with the GB3GF utilities and edited the file by loading into a spreadsheet application

On a Windose workstation download,

Extract the files form the zip archive and then run GD77-CSV(OpenGD77).exe.

Open the Code Plug you wish to edit:

Export the csv file and edit in your favourite spreadsheet application:


Programming Hints

TX Inhibit Quick Key Override: Allows transmission to be sent on a busy channel. The user accomplishes this by double pressing the PTT within one second.

Read this resource to understand some of the GD77's terms and configurations Documentation Help for Radioddity GD-77 / CPS 2.0.5

Note that only analog mode supports this feature.


Frequency Bands

The RF hardware can't technically operate reliably outside these bands.


VK3TBS Amateur Radio Notes - Upgrade to OpenGD77:

OpenGD77 for the Blind Ham:

These pages from Jason Reilly are good resources for the GD77 generally and hardware mods and issues.

Radioddity GD-77 - FAQ Frequently Asked Questions:

Radioddity GD-77 - Tuning & alignment project:

Modifications, hints, tips and technical information for the Radioddity GD-77:

Glenn Lyons VK4PK
Ver:gnl20200807 - pre published v0.9