[sdiy] How to design out "usb noise"?

[cheater cheater]

I mean I don't have a PC that does that right now (currently on a
laptop) but back when this was happening it could be with a completely
static desktop with some windows open (browser or file explorer), just
the mouse cursor moving



On Fri, Feb 9, 2024 at 4:03 PM Mike Bryant <mbryant at futurehorizons.com> wrote:
>
> We used to just have a frame buffer and copy of the cursor area back to the screen, then redraw the cursor one step on.  It sounds like in your case it's doing a complete regenerate of the screen, which tends to indicate more than just the cursor is moving.  Do you have an animated background ?  Or is the thing in 144Hz (or whatever) mode even in non-gaming applications ?
> ________________________________
> From: cheater cheater <cheater00social at gmail.com>
> Sent: 09 February 2024 14:30
> To: Mike Bryant <mbryant at futurehorizons.com>
> Cc: Mattias Rickardsson <mr at analogue.org>; Richie Burnett <rburnett at richieburnett.co.uk>; Synth DIY <synth-diy at synth-diy.org>
> Subject: Re: [sdiy] How to design out "usb noise"?
>
> On Thu, Feb 8, 2024 at 4:36 PM Mike Bryant <mbryant at futurehorizons.com> wrote:
> >
> > I'm afraid that doesn't actually work.
> >
> > If you do everything in 2mS (or any other audio frequency) bursts, you still get repetitive patterns appearing on the memory lines so it still produces audio crap.  You really should do the actual audio processing at 48 or 96kHz, then try to randomise lower frequency actions such as generating envelopes, handling MIDI calls and so on.  I divide the code for these up into 32 tasks, then calculate 31 in a random order, one per each 96kHz timeslot, but always with just the 32nd task being always on the 32nd timeslot which transfers the newly calculated values into the active memory locations all the other DSP processing uses.
>
> Huh, that's super smart! I can also see this being a good sort of
> defense against power-glitch attacks, eg
> https://www.ledger.com/academy/series/enter-the-donjon/episode-4-power-glitch-attack
>
> Speaking of "dsp whine", here's one thing I never understood. Why is
> it that on some computers, while you're moving the cursor across the
> screen, you hear zipper noise in the gpu's coil whine? This has been
> happening forever, it happens with usb-powered mice (so no RF
> interference and no ground loop), various different generations of
> hardware, etc. It would seem absolutely inordinate for the gpu to spin
> up to a high power mode for a few cycles just to process the cursor...
> right?
>
> > ________________________________
> > From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Mattias Rickardsson <mr at analogue.org>
> > Sent: 08 February 2024 15:22
> > To: Richie Burnett <rburnett at richieburnett.co.uk>
> > Cc: Synth DIY <synth-diy at synth-diy.org>
> > Subject: Re: [sdiy] How to design out "usb noise"?
> >
> > Den tors 8 feb. 2024 13:59 <rburnett at richieburnett.co.uk> skrev:
> >
> > ... if the main micro is processing audio in
> > 2ms blocks that results in an ugly 500Hz current waveform that is quite
> > hard to filter out!  You either need a *LOT* of local stored charge or a
> > big inductor to smooth out the ripple of a 500Hz pulse waveform,
> > otherwise it's influence starts to spread across the board!
> >
> >
> > Or you just have to fill your processors to keep them busy at all times. Finally, feature creep is the solution! ;-)
> >
> > /mr
> >
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