Re: reading vic20 or c64 column

Date: Tue, 30 Jun 2015 10:49:03 +0200
Message-ID: <1809921.lyHBaQCn9j@rakete>
On Tuesday 30 June 2015, 11:41:54 Marko Mäkelä <> wrote:
> What you could do is that you could improve the keyboard scanning. Some
> 20 years ago, I made some experiments on the C128. I found that making
> the outputs to all-1 between each scan iteration would reduce the
> shadowing.
> Another idea that you could do is to read the matrix from ‘both
> directions’ (first driving the columns and reading the rows, then
> driving the rows and reading the columns). Remember that you have a
> dedicated CPU for the keyboard, and not just a few hundred 6502 clock
> cycles in a timer interrupt.
> Also, did you check the article in the C=Hacking Issue #6 about keyboard
> scanning:

i made some more tests a while ago when trying to improve VICE a bit, see 
here: (also contains more tech babble in 
the readme :))


Egal ob sich Elefanten lieben oder bekaempfen, Gras wird immer zertrampelt. 
<Indisches Sprichwort>

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Received on 2015-06-30 09:01:19

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