Just a quick update on the OpenGD77 Tier 2 functionality.
I’ve been working on the Tier 2 functionality for the last 2 weeks, and I now have Tier2 “Passive” functionality working, but it still has a some bugs.
Tier2 Passive is the technical name for duplex repeater operation, where the radio known as the Mobile Station or MS for short, gets its timeslot synchronisation from the Base Station (or BS for short), which is the repeater or duplex hotspot.
The main problem is the almost lack of documentation for the HR-C6000 DMR IC that is used in the GD-77. Although we have one data sheet, its the “Simple” version, and is written in Chinese and the diagrams don’t display correctly.
I’m sure that the full documentation pack would not just be this “Simple” data sheet and include application notes and also full documentation of the chip.
But since all I have is the “Simple” datasheet, everything has to be done by trial an error, as I have no way of knowing what the correct way to operate the chip.
For example. Currently in order to differentiate between TS1 and TS2, I seem to need to put the C6000 into a mode where its actually receiving constantly on both TS1 and TS2. I then only decode the audio from the selected Timeslot.
However the C6000 still sends the ID’s and TG’s for both Timeslots to the CPU, and at the moment I can’t see a way to tell which ID is for which Timeslot.
This isn’t a major problem if only one Timeslot is in use, however if both Timeslots on a repeater are in use, the radio displays the ID’s whenever anyone starts transmitting on either Timeslot, even in the middle of an existing transmission that you are listening to.
The other complication is that the MMDVM repeaters and MMDVM duplex hotspots, don’t seem to work in exactly the same way as the Motorola or other commercial repeaters.
I had the firmware working quite well with my duplex hotspot, but when I tried it on a Motorola DR3000 repeater and the audio faded out ever couple of seconds.
Then even when it worked fine on Tx and Rx for Motorola repeaters and duplex hotspots, there was an Rx issue on some MMDVM repeaters.
Anyway. I think the firmware is now almost at the point where I can make a Tier2 Beta version publicly available, if people are initially able to put up with things like the ID’s not displaying correctly.