OpenGD77 Hotspot bug fix to support BlueDV

posted in: DMR, GD-77, Ham radio | 15

Just a quick post for anyone using the OpenGD77 as a Hotspot connected to BlueDV on the PC

I’ve resolved the problem where BlueDV set both the frequency and power of the hotspot to zero when the “DMR” button was pressed.

The problem was a combination of 2 things.

  1. BlueDV seems to send the  Set Frequency command twice. Once when BlueDV initially connects to the radio, and once when the DMR mode is enabled.
    The data in the first Set Frequency command is correct, however the data in the Set Frequency command that is sent when the DMR mode button is enabled seems to be invalid, because the fields which normally contain the Tx and Rx frequencies and also the power, are filled with zeros.

    I’m not sure if this is a bug in BlueDV, or whether there there is a reason the Set Frequency is sent with zero’s for all values, but either way it caused problems in my Hotspot firmware, because I didn’t expect the “host” to send what appears to be invalid data.

  2. My Hotspot firmware had a bug, where i used the master Rx and Tx variables to store the data from the Set Frequency command, before I had checked whether the values for Tx frequency and Rx frequency were valid.
    Consequentially, even though I send a reject back to BlueDV when I had decoded the Rx and Tx frequencies, to indicate to BlueDV that I thought the frequencies were not valued, I’d already stored the value of 0Hz into both the master frequency values, and hence why the screen end up showing 0Hz with a small rounding error since the frequency of 0Hz is not valid

I’ve now fixed the bug in my code, and the firmware now ignores the invalid frequencies and power settings sent by the second Set Frequency command.

I’ve changed the Hotspot version number to v0.0.6, and also to save confusion about the overall OpenGD77 firmware version, I’ve removed the master version number which was V0.3.5, from the Firmware info screen and replaced it with my callsign “VK3KYY”, so that its obvious that this firmware is quite different from the last formal release which Kai did from his HamDV account on GitHub.


As I continue with the firmware development, the best indication of the overall firmware version will be the date as show on the Firmware info screen, and I will update the Hotspot version number, visible in PiStar if changes are made to the Hotspot functionality.


This new version of firmware can be downloaded from the same location as the previous version

I have also tested this new version on my Android phone, by following the instructions by Riku OH1E in his Youtube video, and it worked OK. But I did have some occasional problems, where BlueDV seemed to indicate it was receiving a signal from the net but the OpenGD77 did not transmit.

At the moment I don’t have time to investigate why the Android app didn’t work perfectly, because I am focusing my efforts into making the OpenGD77 firmware support DMR Tier2.


15 Responses

  1. RiKu Bister

    Good job again Roger, it is working well now. thanks for fix and thanks for posting my video.
    Good luck on Tier2, we all waiting it. 🙂

    73’s OH1E

  2. Robert Lowe

    Hi, I like what you have done with this radio. I have been playing around with it and can seem to find the digital monitor off button, the radio will have audio from both time slots on it.

  3. Stef.

    Hello Roger ne Stef. Dl1bh from germany, also in a Groups of developers😎
    Is it possible to reach yiu in telegram or whatsapp?
    Best regards

  4. Roger Clark

    No. To preserve my precious free time and sanity, I don’t use those apps and I am not on social media.

    Currently I am the only person actively developing the firmware. There is not a group of developers.
    Kai (DG4KLU) does not have time to do any more development of the firmware at the moment.
    The only person who I occasionally discus who to program the DMR protocol etc is Colin G4EML, but he is too busy to do any programming at the moment.

  5. Roger Clark

    The firmware is still in the early stages of development.

    I am currently rewriting a lot of the low level DMR code and when it’s finished those sorts of things will be added

  6. Roger Clark


    I have started the Tier 2 development, but it requires a lot of changes to the existing DMR code, not just some additional functionality to be added.

    So it will not be a quick job 😉

  7. ken

    thanks i have bluedv

  8. Stef.

    I have on question, i understood right, gd-77 is now also running with blue dv on a WINDOWS machine?
    Here it s not working; starting blue dv and connecting gd-77: device is not found, what i m doing wrong?
    Which speed must be taken? 230400 and 460800 are not working both,
    best regards, i took the correct com-port!
    Stef., DL 1 BH

  9. Stef.

    So, problem is tixed, as ever sitting between the ears; on 2 m the distance between gd-77 and raspy was to low, although running only 50 mW, now running perfect, only one question left, it s possible to switch over to another reflector, but the answer is not send in tg9, but in the refl. number, problem an the firmware or of blue dv?
    best regards,
    Stef., DL 1 BH

  10. Stef.

    Don t know why, my last sending here was erased…

    Stef., DL 1 BH

  11. Reggie Rapson

    Thank you Roger. If you need anything your need some testing done please give me shout. Also I tried to setup the BlueDv on my phone and it seem to somewhat work. I wont go into detail as you stated you are focusing on the Tier 2 development.Keep up the great work. K8UPE Reggie

  12. Krzysztof

    Great, fantastic job you’re doing Roger! If you need more testers – I could become one (some background in IT but ain’t no C programmer). BlueDV on Lunix/wine works flawlessly (some issues but I was expecting them), no issues with Tier1 on mmdv, having dual purpose HT is the thing!! de Krzysztof SO1Z SP1ATOM.

  13. Carlos Fonseca - CT1GFQ


    Here Is a video in portuguese, of the configuration by CT1HDC and CT1GFQ

  14. Vincenzo

    Buongiorno Roger ho un problema con l’hotspot opengd77, in pratica mi funziona per circa 1 minuto e poi sulla schermata del pi-star “Radio Info” la voce “Trx” rimane in rosso come se rimanesse in trasmissione ma non succede niente. Devo settare qualche parametro in pi-star o sulla radio? Grazie e comunque ottimo lavoro. Vincenzo IU8HVF

    “Hello Roger I have a problem with the hotspot opengd77, in practice it works for about 1 minute and then on the screen of the pi-star “Radio Info” the voice “Trx” remains in red as if it remained in transmission but nothing happens. Do I have to set some parameters in pi-star or on the radio? Thanks and still a great job. Vincenzo IU8HVF”

  15. EA3HGK

    Absolutamente sombroso el esfuerzo que estás dedicando. Muchas gracias y adelante!

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