OpenGD77 firmware update

posted in: Uncategorized | 40

I’ve made a few small changes to the OpenGD77 firmware and uploaded a new version to the daily builds folder on Github (see the link below)


  1. There is a fix to prevent totally incorrect power levels being shown in Hotspot mode, if the PA drive setting in the utility menu was set to values below 775.This was being caused when the calculated power in mW was a negative value.

    I have changed the Hotspot version that is displayed in PiStar to v0.0.51

  2. I’ve changed the beep volume setting to be adjustable in 3dB steps rather than the arbitrary percentage values that resulted from the way I was reducing the audio volume by dividing the amplitude by integers between 1 and 10.

    0dB should be approximately the same volume as the official firmware, 3dB will be twice as loud and 6wB will be 4 times as loud.
    The minimum value is -24db which is barely audible above the physical click of the buttons.

    I have also changed the pitch of the key beep to be roughly the same as the pitch in the official firmware.

    Some users will probably need to adjust their beep volume settings again in the Utilities menu.

  3. I have also prevented the radio starting to transmit if the PTT is pressed during boot-up or during shutdown.


As usual the firmware can be downloaded from


Other news

Over the next few weeks I’m going to start investigating how to implement DMR Tier 2.

Colin G4ELM did some initial investigations into what needed to be added to, or changed in the firmware in order to support Tier 2, but discovered that a partial re-write of the existing Tier 1 functionality would be needed before any work on Tier 2 could commence.


I’ve also noticed that the DMR end of transmission appears to be slightly wrong, because there is an additional audio tone after the DMR 4FSK has finished. This seems to indicate the the PA and Tx is being held on after the DMR DSP chip has completely finished sending all the necessary DMR data (Link terminator frames), so I will also be attempting to fix that small problem.


I may still occasionally add enhancements just as light relief from the Tier 2 work, and I will release bug fixes when necessary, but my primary focus will be on DMR Tier 2.

40 Responses

  1. ON8AD

    Works awesome. I’m running MMDVMhost on a Ubuntu 18.04 Virtual Machine; USB passthrough to the OpenGD-77. 1W out. Probably hands-down the cheapest / most versatile hotspot! Thanks for all the effort you’re putting in!

  2. ken


  3. Roger Clark

    MMDVMHost can be compiled to a Windows exe as well..

    I use Windows for most of my testing, and compile MMDVMHost from the source code using Visual Studio (which is also free), albeit requires registration.

  4. ON8AD

    Hi Roger, yes indeed! Works on a lot of platforms. Just wondering, If I would flash the firmware to a GD-77s – that should work identically as well, no? Same hardware, just no screen on it.

  5. Roger Clark

    Its not the same hardware.

    It has no screen.

    It doesn’t have a keypad.

    It has the rotary switch, but I don’t know what thats connected to.

    Potentially there could be lots of other hardware interconnection differences between the CPU and the antenna switch, PA control, Pre-amp control etc

    So loading the OpenGD77 onto the GD-77S could potentially cause the PA and the RF – Preamps to be turned on for both VHF and UHF simultaneously and destroy the radio

  6. ON8AD

    Hi Roger, ok, fair enough. I was thinking more in terms of PA etc. I have both models, i could comoare them side by side and check where traces go?

  7. RiKu Bister

    can you roger share the winblows mmdvm binaries, as google found only one versio from back dated 2017.
    i know i could recompile it, but well… it takes huge amouth disk space and i need to learn how to use it(and see what need to install). I have done more compilation things at linux.

  8. RiKu Bister

    good news
    I managed to get it working with BlueDV. it even says firmware is opengd77!!
    Bad news there is minor bug. the radio rx frequency is mess up, on screen it says right frequency but however radio wont listen(no green light) at right fq.

    to get it working its abit tricky:
    1. start bluedv for windblows
    2. setup your callsign etc and setup com port same as opengd77
    3. Connect first SERIAL button on (radio will go hotspot mode on right frequency) from bluedv
    4. Connect DMR button (radio will go 0.0001Mhz..) from bluedv
    5. press red button from radio and go vfo mode set desired frequency
    6. disconnect DMR button (radio will do nothing) from dluedv
    7. Connect DMR button again from bluedv (now radio will stay on vfo frequency and it will transmit there)
    however when radio is on Rx mode the frequency read on screen is not right. i think this is the point where something is happening 😀

    in theory this should work with android/ios via lan serial line.. havent tested
    picture of prof:

    – OH1E

  9. Roger Clark


    It looks like the data protocol is different.

    I don’t have time to write a version which is compatible with BlueDV, but as the code is open source, someone else who uses BlueDV could do that

  10. Roger Clark


    But I will need to do a clean build, because I modified it during the development of the OpeGD77 Hotspot to help with my debugging.

    However I will check in case it’s in breach of the license to distribute the binary

  11. Roger Clark

    If you take a look in the source code , specifically files like fw_trx.h , I think that’s where the PA and preamp control pins are defined, and the antenna switch pin etc.

    You could see if they appear to be the same on the GD-77S.

    Those are the most important in terms of not damaging the radio.

    I can’t remember if the LED pins are also defined in that file or somewhere else.

    I think the chance of damaging the radio is low once we know that we are not accidentally tuning on both PAs at the same time, or not changing the antenna switch when in Tx mode.

  12. RiKu Bister

    i must repost this again, it works but needed a trick vfo mode needed to be on DMR mode to get both ways working, here is also qso video demonstrating it will work both directions. maybe on todo list(after tier2 and other things) to check out dmr hotspot manual frequency input, at least improve it abit.

    BlueDV working with OpenGD77 (as hotspot) A radio connected via usb programming cable. plug and play.

    1. start bluedv for windows
    2. setup your callsign etc and setup com port same as opengd77
    3. Connect first SERIAL button on (radio will go hotspot mode on right frequency) from bluedv
    4. Connect DMR button (radio will go 0.0001Mhz..) from bluedv
    5. press red button from radio and go vfo DMR mode set desired frequency
    6. disconnect DMR button (radio will do nothing) from dluedv
    7. Connect DMR button again from bluedv (now radio will stay on vfo frequency and it will transmit there)
    8. the RX will work only someone after has TX something..

    OpenGD77 Facebook group(New, just created)

    Video done by OH1E

  13. RiKu Bister

    Managed also get it working on Android bluedv, there is not much bugs, only frequency offcet is 0.001mhz nothing fancy. plug and play (you need tho install tcpuart to redirect packets to usb)
    YES, a radioddity radio connected directly via programming cable via usb otg to the android mobile phone and it is working.

    This hotspot thing is way more useful than ppl think.. it works everywhere. very good for a temporary hotspot on camps/fests etc, full battery powered without any battery banks etc.

    A picture is posted at new opengd77 facebook group


  14. Roger Clark


    I think I know why it has problems with BlueDV, and I can fix them.

    Please can you explain how configure the Android App to use the OTG cable.
    I tried the Android app but it would not connect at all.

    I tried both the MMDVM_HS and also the Zumspot option.

    I know my OTG cable is working, because it works if I connect a USB memory stick.

    Is there a setting in BlueDV to select USB OTG?

  15. Hardy OZ1MAX

    hey Roger, now i´ve got the bat file to the OpenGD77 to work, but now the Wdi-simple exe is not compatible with my 64 bit system, is there a way to change that ?? it´s regarding to the CPS of GD77 🙂 Tnx for the god work by the way … Hardy

  16. Anonymous

    You need to use network serial and download app called TCPUART to let have network packets routed to serial port(in this case usb/serial inside radio) as bluedv for android devs have not implemented this function to the program…

    TCPUART settings, use port 2000 this need to be as bluedv use only this port. then start USB_UART CONNECT (115200)
    Use TCP SERVER port 2000, then press start.

    now press home button on your device and start bluedv for android

    bluedv settings -> setup
    radio type MMDVM_HS
    enable ser2net -> tap YES
    ser2net IP ->
    save/submit settings

    then press connect and after press DMR “connection to brandmeister button) at top left.

    then it work radio go hotspot mode and it is ready to use

    in theory you also could use ESP with wifi or bluethooth connected directly to radioddity, but that will need an extra power source not convenient.

  17. Roger Clark

    I’m not sure why its not compatible with your system.

    Many other people have used it on 64bit systems

    Its the same file used by my Arduino STM32 core, which has thousands of installs.

  18. Roger Clark



  19. Hardy OZ1MAX

    Hey again Roger, now i´ve got the drivers, but now it wou´nt install it, becaurse of digital signing hmmm, it found the GD77 and i have treid to install it manualy, but it says it should be signed digital for the Win 8.1 64bit, but works 100% on my daugthers 32bit machine .. 😉

  20. Hardy OZ1MAX

    hey again, got it working now, had to disable the lookup for digital drivers, then it´s ok works 100% both BlueDV and CPS now …

  21. RiKu Bister

    here is a short video how setup opengd77 working with android device in hotspot mode using bluedv software
    greetings OH1E

  22. Angelo

    Hi Roger!
    I installed pi-star on RPI3 B, updated and configured everything.
    I installed OpenGD77 on the radio.
    The GD77 correctly transmits the traffic of the pi-star, but does not receive !!
    I set the same frequency to another radio, CC = 1 and slot = 2, but the GD77 does not receive !!
    How can I solve it?

    p.s. opengd77 updated on last commit

  23. Anonymous

    Great Work, thank you !!! Now we need to find a power solution for the GD-77, to get the radio powered with no need of battery. That would enable its use a an official repeater.

  24. Roger Clark

    I opened the base of the charger and removed the PCB.
    Soldered wires to the spring connectors that contact with the battery, and connect those wires to an external PSU which is 8V, 1A.

  25. Johan Hansson

    Hi Roger, I have a question.. I am selling GD77 (As a hobby and to be able to keep servers etc up for Brandmeister). I offer to flash OpenGD77 at NO EXTRA CHARGE for those not willing to do it by themselves. Nevertheless I want to contribute to the project somehow.. Why not setup a Paypal account for donations? //SM0TSC

  26. Roger Clark

    The problem with donations is that for projects with more than one developer, its impossible to divide the donations in the correct proportion to everyone involved.

    So I don’t think it would be possible to take donations to the project.

  27. Johan Hansson

    Can I offer you serverspace for your blog/homepage? //Johan

  28. Roger Clark

    Thanks but I already have hosting, which I pay for 1 year in advance.

  29. Mario

    Hello Roger,
    At first thanks for your work.
    The Hotspot mode is awesome. 😜

    But I hope you have a hint for me:
    With the last two Versions the communication between GD77 and MMDVMHost freezes after ca. 2 hours, only a restart of Radio Host helps.
    Any Idea what is wrong ?

    With the last Version before BlueDV ( ? 0.3.5 ?)
    It works like a charm for 12 or more hours.

    I’am running the latest Version of MMDVMHost on a Raspberry Pi 3A+ with Raspbian Stretch

    73 and thanks de Mario, DC7JZB

  30. Leif OH0KCE

    I’m trying to start up OpenGD77 + RPI 4, but get this in pi-star log:
    Starting logging, please wait…
    E: 2019-09-24 15:52:26.054 DMR, Login to the master has failed, retrying network …
    M: 2019-09-24 15:52:26.054 DMR, Closing DMR Network
    M: 2019-09-24 15:52:26.055 DMR, Opening DMR Network
    E: 2019-09-24 15:52:36.102 DMR, Login to the master has failed, retrying network …
    M: 2019-09-24 15:52:36.102 DMR, Closing DMR Network
    M: 2019-09-24 15:52:36.102 DMR, Opening DMR Network

    Pi-star admin show connected to my wifi and GD77 goto hotspot sreen automatic when start


  31. Roger Clark

    It’s not a Network problem.
    Post your question to the PiStar forum.

  32. Roger Clark

    No don’t know.

    Sounds like it’s something specific to you.

    Also, its still experimental firmware, and probably has bugs.

  33. Jason - N6WBL

    Heard some hams talking about your OpenGD77 project on air and found it compelling. So I picked up a radio and put the Tier I version on it, and I’m really enjoying it. Super ham friendly using it with my simplex hotspot. I’ll test the hotspot radio option soon. Thanks for the hard work and making an open ham friendly firmware. And I’m following the Tier II posts, and love the direction.

  34. Roger Clark

    Tier2 Alpha 2 is currently being tested and I hope to release it next week.

    However neither Tier 2 version currently has Hotspot mode enabled, as the underlying functionality needs to be stable before I can start getting Hotspot mode to work with the changes needed to support Tier2.


    Dear Roger:

    After an error when processing a new codeplug, in which I have set up a boot in password, I cannot read or write the codeplug anymore. It asks the password, which I have put just for digits when setup, and now it’s said wrong password. I don’t know how to fix this mess. The radio is initializing as factory but give rx error and don’t work. I tried downgrade and upgrade the firmware many times. Not success. after it too, so Could please help me.

  36. Roger Clark

    This post is about the Open Source OpenGD77 firmware.
    The OpenGD77 firmware does not have any “boot password” functionality.

    I presume you are using the official firmware.

  37. Rob

    Only for your info , Trying on a orange pi zero and it works perfect no problem at al

  38. KARL alex

    Alguém poderia me ajudar?
    Adiquiri um ht Radioddity e configurei o radioddity no BLUEDV.
    Estou usando o OPENGD77 VK3KYY OCT 26 2019
    Conecto o ht Radioddity no computador e conecto no bluedv
    So que o ht Radioddity não dar portatora( não transmiti) e não tem recepção
    Estou usando apenas o ht Radioddity, cabo e computador
    Gostaria de saber como faço para ativar essa opção de transmissão e recepção?
    Desde já agradeço

  39. Roger Clark

    Thats a very old version of the firmware.

    Please see


    Hello Roger.

    My name is Nelson Saraiva PY2HO Brazilian amateur radio. I want to congratulate you on OPENGD77
    and in this suggest the inclusion of new options!!!

    1) LEDs option: ON/ OFF For the two LED colors (TX red and RX Green)
    i.e. for the TX/RX LEDs and if it succeeds, being possible you can have the option of LED ON
    75%, 50% 25% luminousness and the famous : OFF How the options were made for

    2) Baterry POWER SAVER: OFF/ON option on ON 1:1 1:2 1:3 1:4 1:5 seconds.

    These two options would be added to those created by you in the focus of
    saving battery life. What do you think??

    Sorry for writing errors. I’m using a translator to converrter my text.
    Grateful. 73.

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