Re: Joysticks typical polling freq.

From: groepaz_at_gmx.net
Date: Fri, 13 Dec 2019 16:21:16 +0100
Message-ID: <2104690.WSkiZ4m3nr_at_rakete>
Am Freitag, 13. Dezember 2019, 16:11:37 CET schrieb Mia Magnusson:
> Den Fri, 13 Dec 2019 09:00:22 -0600 skrev brain_at_jbrain.com:
> > I can’t add much more than a hat has all eddy been stated but I will
> > put in this note for paddles, if someone later searches for this.
> > The paddles use 512 cycles to take a reading so there will be
> > absolutely no benefit to reading more than once every 512 cycles.  I
> > agree that’s far too often but just noting the paddle hardware does
> > have an upper bound.
> 
> Interesting!
> 
> My faint memory from trying something as foolish as feeding analogue
> audio (at least via resistors) to the paddle input on my VIC 20 and
> just copy (with the appropriate shifting) the paddle value to the
> volume register in assembler, is that it seemed to take about four
> raster lines to do a conversion. So maybe the conversion is about ten
> times faster in the SID in the C64 than the VIC-1 in the VIC 20.

just to make it clear: its not the paddle (obviously, its just a resistor) - 
its the SID that imposes this limit. there is a capacitor that will charge in 
series with the resistor, and the SID counts how long that takes.

the 512 cycles is also true for the VIC20. on the atari 800 the period is much 
longer (~20ms), the same is true for the Amiga. On the VCS *afaik* its even 
longer than that.

-- 

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<Jutta Ditfurth>
Received on 2020-05-29 23:54:54

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