Detect full 48 bits of last data frame in a D-Star transmission #306
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While testing new support for DV Fast Data, I ran across a particular image that reliably generated a bit sequence that the MDMVM firmware interpreted as an end-of-transmission. I dug a bit and discovered that MMDVM only matches on 32 bits of the last data frame instead of the full 48 bits. See http://www.arrl.org/files/file/D-STAR.pdf section 2.1.2, item (6) for details.
timclassic
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That's excellent work. What I will do is merge this pull request and then modify the code and use only one 64-bit wide bit buffer rather than having two. This should be a transparent change and simplifies the code slightly. |
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That sounds great! |
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@g4klx @juribeparada How do you normally share changes between MMDVM and MMDVM_HS? Should I prepare a PR for https://github.com/juribeparada/MMDVM_HS that includes this change and 9440b43? Or is there some other process that will pick this up? |
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Andy’s repository is the definitive location for the hotspot firmware. I have a copy of it on my GitHub but ultimately his is the master copy.
It would be best to include my code simplification as the CPU on a hotspot is relatively small compared to the modem one.
Jonathan G4KLX
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On Tuesday, December 15, 2020, 01:24, Tim Stewart <notifications@github.com> wrote:
@g4klx @juribeparada How do you normally share changes between MMDVM and MMDVM_HS? Should I prepare a PR for https://github.com/juribeparada/MMDVM_HS that includes this change and 9440b43? Or is there some other process that will pick this up?
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While testing new support for DV Fast Data in g4klx/MMDVMHost#667, I ran across a particular image that reliably generated a bit sequence that the MDMVM firmware interpreted as an end-of-transmission. I dug a bit and discovered that MMDVM only matches on 32 bits of the last data frame instead of the full 48 bits.
(I referenced http://www.arrl.org/files/file/D-STAR.pdf section 2.1.2, item (6))
I'm not convinced that this implementation is the best version of this change, but it does work for me. I tested this patch on both a ZUMSpot (by making the same change against https://github.com/juribeparada/MMDVM_HS) and a Raspberry Pi with a ZUM Radio MMDVM-Pi rev 1.0 board, and the test image no longer generated an early EOT on either system.