OpenGD77 Hotspot mode general Beta release

posted in: DMR, GD-77 | 83

I think the OpenGD77 Hotspot mode firmware is probably stable enough for more people to Beta test it, so I am making it publicly available for download.


Since I’ve now pushed all the source code to GitHub, I’m also updating my “Daily builds” version on github.The latest version of the complete OpenGD77 firmware, including Hotspot mode, can be downloaded from here

This version also has some new features to the non-hotspot use of the firmware, including audible Timeout warning beeps, and DMR audio mute, for use when you only want to receive Private Calls


This firmware can be loaded onto the GD77 using the official firmware loader.

Please Note.

  1. This firmware is still in the early stages of development.
  2. It only supports DMR audio. i.e It does Not support SMS messages at the moment, and won’t support SMS until after Tier 2 functionality is working, as Tier 2 is our priority for our development time.
  3. You use it at your own risk.
  4. It may not be completely stable and is likely to have bugs.
  5. Using high power settings may overheat the PA in the radio, because the radio is not designed to be constantly transmitting.
  6. There is a potential bug where Tx does not turn off. So the hotspot should not be left unattended for extended periods

Default power in the OpenGD77 firmware is approximately 1W, and this is the value that will be used by the Hotspot unless you change either the Power (PA drive) value in the Utilities menu, or you change the RF Level setting in PiStar’s Expert -> MMDVMHost settings.

If you change the power setting in PiStar to any other value apart from the default value of 100%, the firmware will use the value from PiStar.

Hence 99% will give almost 5W, which is unsustainable over a long period of time.

0% will almost turn the PA off completely, but you will find at short distances that the 5mW produced by the AT-1846S  Tx/Rx chip in the GD-77 can still be received.

The power display in Hotspot mode, is currently only a rough approximation of power, as its actually the percentage of PA drive, multiplied by 5000mW to give a mW figure.

However since the PA output is non linear with respect to PA drive voltage this value is not accurate.

If you want to set your Hotspot to a specific power level, which you measure using your own power meter.

  1. Turn off PiStar (Power off)
  2. Exit from Hotspot mode using the red menu key.
  3. The radio will probably now be in VFO mode.
  4. Connect a power meter
  5. Press the * button and look at the top left of the display to confirm the radio is in FM mode (or press * again until you toggle into FM mode)
  6. Go into the Utilities menu, and select a PA drive setting (approx 1700 gives 1W)
  7. Adjust the value by pressing the left and right buttons.
  8. Press the PTT to transmit in FM and confirm the power level
  9. When you are happy with the power level. Press the green menu key.
  10. Turn the GD77 off and on again, go back into the Utilities menu and confirm the power setting has been saved
  11. Exit back to the VFO (or Channel screen) by pressing the green menu key.
  12. Turn PiStar back on, and wait for the radio to enter Hotspot mode.
  13. Make sure the RF level is set to 100%, as this will use the value you just assigned in the radio



83 Responses

  1. RiKu Bister

    well it does it only when dmr signal coming, and never done this on official firmware. i could reinstall original firmware back and read radio codeplug with community cps, send codeplug to you. as i do have only one radio i cant test other radio. where i should send it?

  2. Roger Clark

    I doubt its a codeplug issue, but I’ll send you an email later and you can send me your codeplug

  3. RiKu Bister

    its only thing what we have different the codeplug. now have original firmware and it is working fine no self pressing happening

  4. Roger Clark

    The official firmware does not use all the buttons. The Left arrow is not normally used, and I don’t think the star key is used at all.

    So if your hardware was pressing those buttons you would not see any difference on the official firmware

  5. RiKu Bister

    button sound will come when press button, and it comes only when i physically press it even when dmr signal

  6. Roger Clark

    Very strange

    I really don’t understand why this only happens with your radio.

    Did you load the driver so that the community CPS can backup your EEPROM and Flash.

    I could try loading a clone of your radio if I have those data files.

    BTW. What is your callsign ?

  7. Alister Chapman

    Hi Roger. Excellent work. Just one note from me is that it does not pass SMS messages as a conventional mmdvm hotspot would.

  8. Roger Clark


    Thanks for pointing this our to other readers. I should have probably mentioned this in my post, so I’ll update my post.

    We’ve not implemented SMS messages yet at all with the OpenGD77 firmware, hence why it doesn’t work with the OpenGD77 Hotspot.

    The OpenGD77 Hotspot mode does not work like conventional hotspots which are basically just a transparent pipeline and generally just demodulate whatever 4FSK they receive and pass it to MMDVMHost (PiStar).

    We don’t have access to the 4FSK data decoded by the HR-C6000 DMR DSP chip, so I had to write code to generate the DMR frames from scratch and send them to MMDVMHost.

    So to support SMS messages I need to get SMS Rx and Tx working in the normal operation of the OpenGD77, and after that’s working, I’d have to work out how to generate SMS DMR frames from scratch.

    However, Tier 2 support takes precedence over SMS functionality for our development time.

  9. RiKu Bister

    Heya, my callsign is OH1E, im from Finland.
    there you go, backup done with opengd77 firmware(todays version) and opengd77 supporting cps.
    this is temporary downloadlink, and will expire in few days:

  10. Roger Clark


    I’m downloading now.

    Its nearly 9pm here, so I won’t be able to look at it today, because I also have to backup my less used GD-77 before I install your backup files – in case they break my radio 😉

    Its a very strange problem, and the only other thing I can think I could do is to, is to write some diagnostics that output the keyboard state etc via text on the USB to serial. Because its possible to run any serial terminal and connect to the OpenGD77, however normally it won’t send any information as the serial us used for the CPS and also for the Hotspot mode and sending debugging infomation would prevent both those working.

  11. RiKu Bister

    yeah, that would be ok.
    One more thing you need setup your hotspot to 144.9625 or 434.450 or 434.425(and select zone from radio) to avoid any changes on cps, dont even change dmr id, because you are doing only rx that does not matter. if you can test without touching at all on cps that will be best replication what you can have 🙂

    offtopic: Also noticed opengd77 has the same problem as stock firmware, it wont save last used channel. when powering off radio it will not go on last used channel.

  12. Roger Clark

    The official firmware not saving the channel is a different bug.

    I recently noticed the OpenGD77 isn’t remembering the channel, but I can find and fix that bug. I don’t know if Radioddity will ever fix it in their firmware 😉

    PS. It doesn’t matter if I transmit, my local DMR network blocks traffic that’s not the same ID as my hotspot even if its in public mode !

  13. Roger Clark


    Its now saving the channel.

    Strange… I agree it didn’t seem to be working the other day, but is now.

  14. Miguel Angel Cabrera

    hi my name Miguel my call is cx1rk. i am willing to test that in my gd77, the last version is firmware_V0_3_4.sgl, is that correct.

    many thanks !!

  15. Roger Clark

    You can download from the link in the email.

    However. You should first install the official version 3.1.8 by downloading it from here

    And use the Community CPS to update your codeplug to the current format, because there was a codeplug data format change when the official firmware version 3.1.0 was released, and the OpenGD77 only works with the current codeplug format.

    If you don’t already use the Community CPS, it can be downloaded from here

  16. RiKu Bister

    i have been using gd77 (and all hams on our city about 10 of them) some of them since version 2.x.
    i moved on to 2.x community, cps then 3.0 and then 3.1. always used community cps when it was available. codeplug is very big it has alot of channels, so we have just upgraded from old to new as steps mentioned. it works fine with factory firmware. So basically if i have this problem, all other our city hams will have same thing because i have programmed them exactly same way.

    Okey i have created new blank codeplug just put my dmr id and well… it not works lol still doing the same arrow moving things on vfo mode. Take a look on i have uploaded empty bins, so those are dumped now after creating empty codeplug.

    I havent tried yet dumps on email, as you said it will be risky, doing as last resort.

  17. Eaden

    Greetings, and thank you for great work.

    I did tried firmware, after I connect and start pi zero gd77 switch to hotspot mode but system is not working , in pi star dashboard I see noting. Do you have any ideas why?

  18. Roger Clark

    I did you install the firmware

    Did you update PiStar to the latest version

    Did you change the mode to “OpenGD77 DMR Hotspot (USB)”

    The GD-77 needs to be connected and turned on when PiStar boots, or it won’t connect

  19. Eaden

    Yes I did install –>
    I used V3.4.17 for pi-star
    I used zum limba

  20. Roger Clark

    Probably a USB connectivity issue

  21. Roger Clark

    This firmware is experimental at the moment and not intended for general use.

    I can’t replicate your problems even if I restore your data onto my radios.

    Please wait for the final release when the firmware may be more stable.

  22. ea4gvrtony Gomez

    Hi, this is EA4GVR, Tony, Madrid Spain
    Just out of curiosity, I have1 gd-77 and 1 GD-77S, just wondering if I can use the GD-77S in the same way. No screen but the radio is the same. If yes, I would use the non-screen version as hotspot. Thanks for all your effort and dedication.tony, 73

  23. Roger Clark

    It won’t work on the GD-77S without modification.

    The GD-77S uses a different encryption key, so the firmware will be rejected by the radio.
    Also the firmware would not work because it would receive false triggers from the keyboard inputs which are not connected.

    Please note, due to commercial companies in Sweden now making money from selling the OpenGD77 firmware for their own profit, I have currently ceased doing any more public works on this project.

    I will continue to work on the project for my own private use, but will no longer be making any more updates public.

  24. RiKu Bister

    what you mean companies in sweeden, tell us more? any source of this info? it is against opensource rules to gain profit!!

    Anyway, i have now tried almost everything.
    flashed to lowest firmware i can find, done factory reset from radio(memory reset) then upgraded back, dident work
    also i managed to put your version Roger what you send me on email flash version. after that again downgraded firmware to lower one to do factory reset, then problems started, radio volume needed to be full to hear static, radio was not on frequency etc. also after doing factory reset via buttons on radio many times, it every time took your callsign and your settings to the radio(even i put empty codeplug and after that reseted), very odd !! so it seems it never emptied the flash any way, luckily i did have my backup from flash that bring radio back alive.

    so what i see my radio is full of garbage at eeprom/flash there is no way to get them on factory setting/emptied i tried now everything what i know, i did reload empty codeplugs etc..
    The eeprom is always 2.06-03 i was not able change that anyway. Maybe the radio is different version somehow, i do have very old/early model of gd77. all firmwares what i tried, belive me i have flashed alot today.. none of them haved button pressing itself, only opengd was having that problem (only when DMR rx was traffic) mode. so there must come packet on rf and there is some function on the code what reads it from there and do the pressing, i dont find any other options. maybe try earlier versions? 0.1?

    riku / OH1E

  25. Roger Clark

    I don’t want to post a link, but there is a Swedish company selling the GD-77 with the OpenGD77 as an option.

    They were charging an extra 200kr for the OpenGD77 option, but now seem to not charge any extra for this option.
    I know several people have sent strong emails to them about this, and perhaps this is why there is now no additional charge.

    I think Radioddity will also contact them, because its a problem for them if people damage their radios by trying to run 5W as the hotspot, because the GD-77 is not designed to run 5W continuously, which would happen if they were tuned to a very active TG like BM TG 91.

    Re: You radio

    I’m afraid I have no idea why it does these things.

    I modified the CPS (and uploaded a new version to github), which now allows any EEPROM to be restored, and I restored your EEPROM and Flash to my oldest GD-77, which is probably 18 months old, but I could not replicate the problem.

    Possibly there was some change in the hardware design, and the official firmware may have 2 modes of operation of the keypad etc.

    I have a schematic of the GD-77 but its not completely up to date, and I don’t 100% trust the connections which are shown on the schematic, because I think Radioddity (TYT) make small changes to the radio hardware without telling anyone.

    Specifically, I have noticed that the 2 new GD-77’s which I have as samples from Radioddity, do not have the problem of the squeak on the audio if the battery is charged more then 8V.

    My old radio squeals if the volume is low and there is a signal and the battery is above 8V.

    So I think Raioddity / TYT made some change to the amplifier components to fix this in the more recent versions.
    I know Jason VK7ZJA sent Radioddity details of how to change the R and C values in the audio PA circuit to fix the squeal, and TYT may have used that information to fix the problem

    What I find strange with your problem, is that the problem only occurs when you receive a signal.

    I looked in your Flash memory and you don’t appear to have a DMR ID database loaded, so you could try loading that using the DMR ID section in the Community CPS, but even without the DMR ID loaded in your Flash, my radio still worked fine.

    I also wonder whether it only happens in DMR mode, and perhaps only on repeaters or does it also happen on simplex?

    I wish I could help more, but since I can’t replicate your bug its very hard to fix it 🙁

  26. RiKu Bister

    This is very sad to read, someone making profit for it.
    i have always running as low power is possible to avoid final blow. actually setting txpower from radio it will be less than setting number 1 to mmdvm.conf

    my radio squeals above 8volts, its a known issue.
    It happens also when pressing ptt the arrow button sound, not only on receive.

    I will try later today restore your eeprom file and see what happens.

    I know this is hard, i wish it was easy send radio to you:) i might loan other radio from my ham friends, or just buy another. we see it.

  27. lesmarvois

    Good evening, Rodger, Can we flash with the firmware a GD77S.
    Thank you

  28. Roger Clark

    No. Not without major changes.

    See my replies to other people about this.

  29. Roger Clark

    I would try borrowing another radio and see if it has the same issue.

    The official firmware can be reloaded before you give it back to the owner.

    The OpenGD77 firmware uses a small amount of the EEPROM to store its own settings for the VFO and display brightness etc, but we use the end of the SMS message store area, which hardly ever used.

    So you should have no problems when you reload the official firmware.

    At the weekend I will write you a special version of the firmware which will send debug text messages via the USB serial, and you can try that version and perhaps we can work out whether the firmware thinks the keypad is being pressed or whether it is some other problem

  30. RiKu Bister

    okey, thanks for info.
    I did look the code yesterday, even tried 0.0.1e version, that do also same thing lol!
    maybe if i can find source code for older version, that would easier to modify because less stuff there and recompile it. it gotta have something to do with gpio pins from keypad, if just start changing them spontaneously and see what happen.

  31. Roger Clark

    Its really strange that it only seems to be receiving these keypresses when its receiving a signal.

    This implies that perhaps the problem is not really that the keypad is being pressed, and that its some sort of buffer overflow in the code which is causing the keypresses.

    However I don’t know why, only you would be getting that buffer overflow.

  32. fabian

    hello I have the problem that the device is not recognized with any of the codeplug probe with the 3.1x and it is also not about updating the handy again and it does the most it is as if the sof did not recognize the gd77

  33. ta3iac

    merhabalar bende GD 77 ile hotspot olarak kullanmak istiyorum fakat başarılı olamadım son güncel hotspot güncellemsi nedir adresine gönderim yaparsanız sevinirim TA3IAC 73

Leave a Reply