OpenGD77 Hotspot PiStar update

posted in: DMR, Ham radio | 24


The configuration screen having a new Modem option of OpenGD77 DMR hotspot (USB)


And the Dashboard now displays the name and the firmware version


A note to the Beta testers.


Your versions won’t display the version number correctly, as I only added this today and I have not send out an update with the version number included.

I’ve been making some enhancements to Hotspot mode today, so that the display on the GD77 uses the DMR ID database to look up the callsign and name, for both Rx and Tx functionality


I’m also working to add power control via PiStar, but for that to work, I also need to add the general functionality to read the High and Low power PA drive values from the calibration data in the Flash memory and also build a look-up table to convert from required power values in milliWatts to PA drive values.

Because as you can see from the graph below, the relationship between PA drive level (voltage) and power output in mW is not linear.


The blue line in the graph, is record values from VK4JWT’s radio on 437.5 and the green line was my attempt to calculate the value using a quadratic equation.

However, I think its going to be easier to manually build a look-up table an interpolate between values


One other thing I noticed is that the power calibration on my radios is not that accurate. One radio was putting out 4.6W when it should have been 5W, so I’m not sure if the factory power calibration values are that accurate.


24 Responses

  1. Fabio

    Hi Roger, I have installed the first firmware version opengd77, I would like to try the firmware otspt as a beta tester. I would be happy if I sent the firmware to 73 de iz2bks Fabio.

  2. Marko YT5HOK

    Hi Roger,

    Following your work since the beginning. Amazing job done!

    Just one idea for you… Two GD-77, Raspberry Pi with two USB ports… Mobile repeater! 🙂

    Best regards,
    73 de YT5HOK

  3. Roger Clark

    I thought about that, but its not possible, because the 2 radios need to be locked in very close synchronization which I don’t think would be possible via USB

  4. Marko YT5HOK

    Never mind. Keep up the good work.

    There are more then few of us (AROs) here in Serbia following your work. GD-77 is very popular here, cause it’s good enough and cheap.

    Best regards to you and the other guys on project,

    Tried to contact you via DMR couple of minutes ago to express our appreciation, but you were unavailable, so I’m writing here instead.

    73 de YT5HOK

  5. Roger Clark

    I’m hoping to release publicly very soon.

  6. Roger Clark

    Hi Marko

    Its getting late here, so I turned off my radios etc.

  7. Yolanda

    I want to have a try. But It’s a pity, I have no GD-77. I have Ailunce HD1. Will you have this radio plan?

  8. Roger Clark

    Hi Yolanda

    No. Its not possible to support any other radios, since each radio is different.

    Also the reason that this is possible at all on the GD-77 is that the firmware encryption was cracked by DG4KLU.

    It may be possible for the MD-380 dev’s to port the code to that platform, since they have also cracked the firmware encryption for that radio and know a lot about its hardware, but personally, I would not ever have time to undertake development on any other radio

    The OpenGD77 project has taken several thousand man hours already just to get this far, and its not complete as Tier 2 DMR is not supported yet

  9. frederic bonnet

    Bonjour Roger, J’ai installé la première version du firmware Opengd77. J’aimerais essayer le firmware en tant que bêta-testeur.,
    Cela fonctionne très bien entre le pi-star et le gd77 .Le gd77 conserve toujours ses menoires et je trouve cela impeccable.Je l’utilise avec votre dernier CPS. Je serais heureux si j’envoyais le firmware à fredbonnet@☻ 73 de Fred.

  10. Roger Clark

    I have now released all the changes to Github. See my more recent posts

    The daily build file can be downloaded from Github


  11. Justin Korpal

    I would like to sign up as a beta tester. Plan on starting this this week. Please send me the firmware at

  12. Roger Clark

    Hi Justin

    Please see my latest post.

    I’ve now made the Beta version available for anyone to test.

    So far the majority of people tell me that its working fine for them.

  13. barış

    baofeng rd-5r will

  14. Roger Clark

    Possibly in the long term

    The RD-5R shares most of the same chipset as the GD-77, (MK22 CPU/MCU, HR-C6000 DMR DSP, AT-1846S TRx, EEPROM etc) but has a different screen.

    However the interconnection between the MK22 MCU and the other chips seems to be different on Baofeng radios to the GD-77, so even if a new display driver was written for the display in the RD-5R it would not work, because all the connections are different.

    If someone has a schematic diagram for the RD-5R, it would make things easier to convert, because the connections between the MCU and the other chips would be easy to see.

    The same applies to the Baofeng DM-860/DM-1801 . This radio looks like a clone of the GD-77, but when I tried to load the OpenGD77 onto my DM-1801 only the display worked, and part of the keypad. It would not transmit or receive etc, so I presume the CPU connections must be different and I don’t have a schematic for the DM-1801 either

    The firmware is open source if you want to create a version that works for those radios.

  15. barış

    Thank you very much for your quick reply

  16. Matt Fairbairn (M6SEU)

    Hi Roger.
    All been running well today. Ver 0.0.3 according to Pi-Star 4.9.35-v7+. Had a wee problem getting it to TX but sorted by connecting GD77 then boot Pi3 and works every time done that way.
    Super work Sir.
    Cheers Matt

  17. Fabio damiani

    Hi Roger, with firmware 0.0.3 I found occasionally that the gd77 remains in tx infinity, tot 180 sec does not work and only turning off the radio resets. Pi-star works correctly in RX but GD77 remains TX. 73 de iz2bks Fabio.

  18. Roger Clark


    I don’t know whats causing that, but I think it may have happened to me once when I was testing.

    When it happened was the screen displaying the power etc, or displaying the data about the station ID etc

    I’m going to put in an emergency Tx Off command if the Tx is on and the mode is Rx but its hard to know precisely why this is happening.

    I suspect its being caused because the way the Tx takes a while to shut down while it sends the “Terminator” frames after a transmission has ended.

  19. Fabio Damiani

    Thanks Roger, great work, excellent sound and with 1 watt external antenna I cover 10 km around my city!

  20. Roger Clark

    I’ve uploaded a updated version to

    Which checks in Rx mode whether Tx is still enabled, and if so turns it off. However I don’t really know what conditions cause the problem you have described, so I don’t know if this will fix the problem.

    Tx should finish if PiStar puts the Modem into IDLE mode, or if it runs out of data in its Tx DMR frame buffer.

    I’ll email you about this

  21. Anonymous

    Hi Rodger
    Could it be possible to number or date stamp the firmware updates. At the moment it is only called firmware.
    Best George

  22. Fernando

    hi, greats work. have a litlle bug
    M: 2019-09-10 19:38:20.665 DMR Slot 2, received RF voice header from CE4RAY to 730997
    M: 2019-09-10 19:38:24.447 DMR Slot 2, received RF end of voice transmission, 3.6 seconds, BER: 0.6%
    M: 2019-09-10 19:38:27.720 DMR Slot 2, received network voice header from 730997 to CE4RAY
    E: 2019-09-10 19:38:29.936 No reply from the modem for some time, resetting it
    M: 2019-09-10 19:38:29.936 Closing the MMDVM
    M: 2019-09-10 19:38:31.937 Opening the MMDVM
    E: 2019-09-10 19:38:44.754 Unable to read the firmware version after six attempts
    M: 2019-09-10 19:38:49.755 Opening the MMDVM
    wen speak in parrot for example, lost conecction and dont TX my parrot, hardware GD77B (black display) + Pi 3 Model B (1GB) thank you

  23. Fernando

    fine, work fine with 253mW… more power generate more RF, grettings ce4ray – Chile

  24. Roger Clark

    Not really, I would also have to constantly update the link URL in my blog, many times a day.
    And it would break the link for anyone who shared it via email etc

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