[sdiy] Generating a large number of CV outputs

[Mike Bryant]

Yes.  The original SPI 'spec' stated a maximum number of words per transfer so that everybody supported that, but some MCUs just extend it to infinity subject to DMA and memory limits.

________________________________
From: Jonatan Liljedahl <lijon at kymatica.com>
Sent: 11 December 2023 16:47
To: Mike Bryant <mbryant at futurehorizons.com>
Cc: SDIY <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Generating a large number of CV outputs

Maybe that was the problem then! What exactly is continuous mode? No gaps between words?

/Jonatan
http://kymatica.com


mån 11 dec. 2023 kl. 17:00 skrev Mike Bryant <mbryant at futurehorizons.com<mailto:mbryant at futurehorizons.com>>:
Using SPI requires continuous mode which I'm not sure most STM32s support.

________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org<mailto:synth-diy-bounces at synth-diy.org>> on behalf of Jonatan Liljedahl <lijon at kymatica.com<mailto:lijon at kymatica.com>>
Sent: 11 December 2023 15:49
To: SDIY <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>

Subject: Re: [sdiy] Generating a large number of CV outputs

I did a similar plot when I was experimenting with
sigma-delta/noise-shaping output from an STM32, but in ASCII :)
There's one trick where an SPI peripheral is used for "high quality"
audio PDM output, but I never was able to get any usable performance
from it. I even got better results just using 8 bit PWM but with
sigma-delta noise shaping. (But I settled on using the built-in 12 bit
DAC instead)

Cheers
/Jonatan

On Mon, Dec 11, 2023 at 4:19 PM Roman Sowa <modular at go2.pl<mailto:modular at go2.pl>> wrote:
>
> This is awesome! Such a simple trick helps to visualize it so quickly.
> Testing different patterns to further minimize any repeatability seems
> like pleasant adventure now and doesn't even require any test equipment.
>
> Roman

--
/Jonatan
http://kymatica.com
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