Re: MMDVM & UDRC

Jonathan Naylor
 

Hi Annaliese

I've done the changes to use a 48 kHz sample rate with the MMDVM-UDRC. I'm making no guarantees but the values are based on the working 48 kHz branch of the main MMDVM firmware. The only area that bothers me is the output level for POCSAG which may be very out compared to the others.

This version should at least allow you to test with the UDRC and iron out any bugs.

I'd be very interested in any problems you find, and of course any pull requests that you may make to fix them. Remember that the DMR in this version is simplex only. Using the UDRC or similar hardware makes it impossible to have the type of synchronisation that duplex DMR repeating requires.

Jonathan  G4KLX


On Friday, 7 December 2018, 10:18:47 GMT, Annaliese McDermond <nh6z@...> wrote:
> On Dec 7, 2018, at 12:14 AM, Jonathan Naylor via Groups.Io <naylorjs=yahoo.com@groups.io> wrote:
>
> Hi Annaliese
>
> There are a set of filter coefficients for 48 kHz sample rate in a branch of the MMDVM firmware. I’ll look into slotting those in and altering the other variables.
>
> Ideally I’d recalculate them in MATLAB as floating point but my license for it ran out. Octave can probably do it though. Even rescaling from Q15 format will probably give enough precision.

If you have some matlab code, I have a Matlab 2015b license on my Mac that I could spit out the coefficients for you.  I’m mildly familiar with the process because I’ve done it for filter coefficients in the OpenHPSDR FPGA code that I was playing with.


> It’s bizarre seeing Linux kernel AX25 being mentioned. I wrote that stuff 23 years ago and last looked at it 20 years ago. I’m not sure I could add anything to that discussion these days.
>
> Jonathan G4KLX

--
Annaliese McDermond (NH6Z)
nh6z@...



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