Open jamesham opened 3 years ago
The MMDVM could do it easily, do you have any suitable radios with TX/RX changeover time of 1ms or less to do it with?
Anytone 878 seems to support it. Can MMDCM on pistar can be configured to do it?
No. I have no programming information about it. If you find it, let me know.
TDMA direct mode (DCDM) is documented in the DMR standards documentation. https://www.dmrassociation.org/dmr-standards.html Part 1, Sections 4.4.4, 4.6.2, 4.6.3, 5.1.4.6, 5.2.2.4, and more. I think TDMA direct mode is getting pretty popular, at least all the DMR Tier 2 radios I know of support it, including the ever popular Anytone 878, GD-77, DM-1701, MD-UV380/390, etc etc.
This could be a huge revolution for hotspots. If there are no other constraints, a "simplex" hotspot could function with two timeslots, as the air interface specs a bidirectional channel with guard time. I think it could be a great step forward, eliminating the need for and cost of two RF interfaces.
That's all very well, but can you find suitable hardware that can do the fast switching reliably? Have a look at the timing requirements, they're very strict. It'd be very easy to do in software, but suitable hardware is lacking. On Friday, 10 May 2024 at 09:00:01 BST, J. Chang @.***> wrote:
TDMA direct mode (DCDM) is documented in the DMR standards documentation. https://www.dmrassociation.org/dmr-standards.html Part 1, Sections 4.4.4, 4.6.2, 4.6.3, 5.1.4.6, 5.2.2.4, and more. I think TDMA direct mode is getting pretty popular, at least all the DMR Tier 2 radios I know of support it, including the ever popular Anytone 878, GD-77, DM-1701, MD-UV380/390, etc etc.
This could be a huge revolution for hotspots. If there are no other constraints, a "simplex" hotspot could function with two timeslots, as the air interface specs a bidirectional channel with guard time. I think it could be a great step forward, eliminating the need for and cost of two RF interfaces.
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So we're getting closer to the edges of my knowledge here, but is it the timing aspect that disqualifies the AD7021/current MMDVM_HS boards?
What about the S2-LP with an STM32? I think there's a sufficient clock on that setup.
Or even this Auctus A6/A7/A8. It's the same integrated chip that powers the extremely low cost COTRE DMR portables, among others. The single integrated transceiver and controller must be very cheap, and I can confirm it is capable of DCDM. If I can get a data sheet I'll return with that.
Also the Si4464 looks very promising and explicitly mentions TDD in its data sheet. I will investigate.
Based on some discussion on the Pi-Star Facebook group, I started to wonder if MMDVM systems could support DMR Dual Capacity Direct Mode (DCDM). I don't think this is something MMDVM currently supports. Is there a reason it couldn't be added? Or just not popular enough to justify the development?
I saw that this was asked a few years ago, but the issue, #161, was closed without comment.