[sdiy] Techniques for Multiplying MIDI Clock frequency?
synthimuse at gmail.com
Fri Dec 17 18:24:32 CET 2021
The clock multiply technique I used ( just once ) is that I just outputted
multiple midi clock messages for every incoming clock message.
I measured the incoming clock period so that when I was sending multiple
clocks out, I spaced them appropriately between incoming so there was
minimum jitter in the outgoing stream.
The max practical speed I was working to was 250bpm. This would equate to a
clock pulse every 2.5mS.
I suppose I implemented a coarse DPLL and it worked ok, with the limitation
on maximum speed.
I'm afraid the code is long lost or I would happily pass it to you.
On Fri, Dec 17, 2021 at 10:50 AM Roman Sowa <modular at go2.pl> wrote:
> Measure incoming clock period with a timer. Then divide that measured
> timer value by the number you want to multiply the frequency. If you say
> anything between 10 and 100 is fine, then dividing by 32 sounds like
> walk in a park. And that divided value (or simply shifted in case of 32)
> is then loaded as period for another timer that outputs a pulse on
> This way after each incoming clock pulse you get immediate response of
> updated frequency multiplied by 64 (or whatever other value)
> W dniu 2021-12-17 o 08:03, Spiros Makris via Synth-diy pisze:
> > Hello List,
> > I want to experiment with polymetric structures and create "non
> > standard" subdivisions within the standard ones supported by MIDI. I
> > have only worked with the 24ppq, using the timing messages to directly
> > drive the sequencers. I would like a way to multiply the clock frequency
> > in order to increase resolution, let's say by 10 or maybe 100 times, if
> > that's feasible (I think it is?).
> > I think this is achieved by a PLL. I understand the basic concepts of it
> > and have used in the analog domain, but never did it in a digital only
> > format. Furthermore, I suppose having an array of hardware peripherals,
> > such as timers and interrupts, and a fairly fast processor (teensy 3.2)
> > could open up other approaches that don't follow the standard PLL
> > configuration.
> > This has been on my mind for some time, but I don't really know where to
> > start. Any advice, or resources are greatly appreciated
> > Regards,
> > Spiros
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