[sdiy] Techniques for Multiplying MIDI Clock frequency?

[Mike Bryant]

I would choose a cheap $1 ARM M0+ processor with a fast clock – STM32G03 or RP2040 for example.  You can then run a tight loop which samples the input and modifies the increment on a software accumulator, outputting the top bit of the accumulator as the new timer.   Jitter will be clockfreq divided by looplength which should give better than 100nS with careful coding.

From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Spiros Makris via Synth-diy
Sent: 17 December 2021 07:03
To: synth-diy mailing list
Subject: [sdiy] Techniques for Multiplying MIDI Clock frequency?

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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