[Solved] MMDVM Repeater w/ HBlink

NA7Q
Posts: 151
Joined: Wed Jan 01, 2020 3:41 pm

[Solved] MMDVM Repeater w/ HBlink

Post by NA7Q » Thu Apr 02, 2020 11:10 pm

I just built an MMDVM repeater. I have an interesting problem that only exists on the OpenGD77 firmware.
If I tune my MMDVM repeater using MMDVMCAL, I can fine tune the transmitter as necessary and use the test pattern calibration for CC1 ID1 TG1 and it works with no issue as simplex. Now when I put everything into repeater mode. The radio decodes nothing voice wise. All my commercial gear, and secondary GD77 with stock firmware running, has no issues decoding. Sometimes when I unkey, my callsign will appear on the radio. Parrot or other users are not heard or displayed.
I suppose it does decode some stuff, but it's in a really bad chop.
Last edited by NA7Q on Wed Apr 15, 2020 11:02 pm, edited 2 times in total.

User avatar
EB3AM
Posts: 204
Joined: Fri Jan 24, 2020 1:40 pm
Location: Catalonia, not Spain
Contact:

Re: MMDVM Repeater

Post by EB3AM » Fri Apr 03, 2020 12:23 pm

It has not been clear to me whether, once tuned to the commercial radio, the opengd77 is working properly.

I also just made a UHF repeater, from an old "Standard RP80" and an MMDVM, and until I found the way to properly modulate the transmitter I had a lot of problems.

What kind of radio did you work with? I am the first time I didn't use Motorola, and it was a little difficult for me to find the problem.
Screenshot-2020-04-03-002435.png
Screenshot-2020-04-03-002435.png (438.73 KiB) Viewed 5338 times
In my case, the TX signal was cut off at just 2khz and not wide enough to send all the DMR data. Fusion, on the other hand, was working properly.

oh4va
Posts: 25
Joined: Sat Mar 07, 2020 7:14 am

Re: MMDVM Repeater

Post by oh4va » Fri Apr 03, 2020 2:50 pm

We have here in Mikkeli, Finland, an MMDVM based repeater. My GD77 w/ OpenGD77 firmware works with it fluently, not any problems so far.

73 de VA

NA7Q
Posts: 151
Joined: Wed Jan 01, 2020 3:41 pm

Re: MMDVM Repeater

Post by NA7Q » Fri Apr 03, 2020 5:24 pm

I'm using Vertex VX-2200 radios. I have adjusted everything within the proper specifications to make it work by using an SDR receiver. It is only the OpenGD77 that it will not work with. It seems okay when on simplex mode. That's what is so odd about it. No problems with stock firmware or other radios when on simplex or duplex mode. I'll try playing with it a bit more after the weekend.
I spent several hours thinking the repeater wasn't working with DMR, though it was, just not with OpenGD77. My GD-73 has always required very finely tuned specs for MMDVM. However it works flawlessly.

Thanks for the reply guys. I will look into it some more and post here if I fail or succeed.

VK3KYY
Posts: 7484
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: MMDVM Repeater

Post by VK3KYY » Fri Apr 03, 2020 7:54 pm

There is probable some secret sauce which we may be missing, which controls the DMR chip internal operation.

However as there is incomplete documentation for the DMR chip is very hard to know what that secret sauce is.

I recommend you hook up a logic analyser to the C6000 and compare the commands the official firmware sends to the commands the OpenGD77 sends.
Look for anything that appears to be filter parameters

oh4va
Posts: 25
Joined: Sat Mar 07, 2020 7:14 am

Re: MMDVM Repeater

Post by oh4va » Fri Apr 03, 2020 8:50 pm

NA7Q wrote:
Fri Apr 03, 2020 5:24 pm
I'm using Vertex VX-2200 radios.
Our repeater has Motorola (ex. Vertex) VX-2100 UHF transceivers and GD77 with OpenGD77 works fine. Should be compare our repeater radio settings?

73 de vA

NA7Q
Posts: 151
Joined: Wed Jan 01, 2020 3:41 pm

Re: MMDVM Repeater

Post by NA7Q » Sat Apr 04, 2020 12:04 am

oh4va wrote:
Fri Apr 03, 2020 8:50 pm
NA7Q wrote:
Fri Apr 03, 2020 5:24 pm
I'm using Vertex VX-2200 radios.
Our repeater has Motorola (ex. Vertex) VX-2100 UHF transceivers and GD77 with OpenGD77 works fine. Should be compare our repeater radio settings?

73 de vA
I recognize your callsign now. I emailed you a couple weeks ago asking about these radios. I have an LTR trunking version of the radio which has a band split for 450mhz to 512mhz. I had to hex edit to get it out of band down to 440mhz. It's just unexplainable why OpenGD77 would make a difference on it all.
I will report back after the weekend when I get back home and spend a few hours working on it. I would surely appreciate your help and guidance. Thank you!

NA7Q
Posts: 151
Joined: Wed Jan 01, 2020 3:41 pm

Re: MMDVM Repeater

Post by NA7Q » Sat Apr 04, 2020 12:06 am

VK3KYY wrote:
Fri Apr 03, 2020 7:54 pm
There is probable some secret sauce which we may be missing, which controls the DMR chip internal operation.

However as there is incomplete documentation for the DMR chip is very hard to know what that secret sauce is.

I recommend you hook up a logic analyser to the C6000 and compare the commands the official firmware sends to the commands the OpenGD77 sends.
Look for anything that appears to be filter parameters
I'm wondering if this is the case. I'll spend some time toying around with things and see what I can figure out.

VK3KYY
Posts: 7484
Joined: Sat Nov 16, 2019 3:25 am
Location: Melbourne, Australia

Re: MMDVM Repeater

Post by VK3KYY » Sat Apr 04, 2020 3:28 am

The official firmware seems to send other streams of data to the C6000, but its impossible to know whether that data is necessary or just boiler plate code for some other functions e.g. FM audio processing, which neither the official or the OpenGD77 firmware use.

I have tried removing the stream of 0xAA's that gets sent to the C6000 by the OpenGD77 (as Kai must have found this in the Official firmware), but it seemed to make no difference to the operation of the radio at all

Hence why I'm not convince that just because the official firmware does something, that its actually needed, or even the correct way to do it.

By looking at the decompilation of the official firmware, using Ghirda, the code didn't look that good, hence it also doesnt give me much confidence about relying what the official firmware does.

oh4va
Posts: 25
Joined: Sat Mar 07, 2020 7:14 am

Re: MMDVM Repeater

Post by oh4va » Sat Apr 04, 2020 6:38 am

NA7Q wrote:
Sat Apr 04, 2020 12:04 am
I recognize your callsign now. I emailed you a couple weeks ago asking about these radios. I have an LTR trunking version of the radio which has a band split for 450mhz to 512mhz. I had to hex edit to get it out of band down to 440mhz. It's just unexplainable why OpenGD77 would make a difference on it all.
I will report back after the weekend when I get back home and spend a few hours working on it. I would surely appreciate your help and guidance. Thank you!
Okay, nice to meet you on this forum as well. I hope you can sort this problem out soon.

I'm very new with GD77, I got my first radio one week ago. I have done some firmware source code modifications to back light functions and more is yet to come. The code is here in a forked repository https://github.com/oh4va/OpenGD77/tree/dev_oh4va

73 de VA

Post Reply