DDCMP sync?

Paul Koning paulkoning at comcast.net
Tue Jan 26 15:39:19 CST 2021

> On Jan 26, 2021, at 2:35 PM, Mattis Lind <mattislind at gmail.com> wrote:
> Hello Paul,  
> ...
>> The framing is different but no harder, I think.  And I was thinking of leaving the protocol state machine to the host, so the microcontroller would only do framing -- deliver completed good frames to the host without interpretation.
> I made a very quick check on DDCMP. It looks a bit like BSC but using a byte counter rather than various characters to end the frame. That would probably simplify the software. It seems to use SYN SYN which is identical to BSC so that part of the code that takes care of framing could probably be used directly. 

Yes, though the sync byte has a different value, the fact that it's called SYN is a bit misleading if you're used to the SYN used in BISYNC.

> There are also the small STM32F411 Weact boards out there (https://github.com/WeActTC/MiniF4-STM32F4x1). 100 MHz and the ART accelerator. From other projects where I have used the STM32F103 have seen that it executes slower than I expected since it was reading code from flash. The ART accelerator should help here to achieve near zero wait state so perhaps 1 Mbit/s would be possible?

What is an ART?  I looked a bit at that Weact thing but got lost in the fulminating about "pirated" copies.  Seriously?  Open source designs are meant to be copied; "pirated" is a nonsensical term.  Low quality copies, that would be a valid complaint.  (The use of leaded solder, all things equal, increases quality rather than reducing it, by the way.)

The ARM chips used in the Adafruit boards I've used have on-chip flash so I'd assume that runs quickly, but I'll have to try to find out.

> ...
> If you have further questions feel free to ask. Would be nice to add DDCMP support as well! Then perhaps I could try those M8203 / M8207 boards I have sitting here.

Thanks, will keep that in mind.  What sort of connection and signaling do your DMR boards use?


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