Re: reading vic20 or c64 column

From: Gerrit Heitsch <>
Date: Tue, 30 Jun 2015 11:55:12 +0200
Message-ID: <>
On 06/30/2015 09:46 AM, Marko Mäkelä wrote:
> On Tue, Jun 30, 2015 at 09:18:52AM +0200, Didier Derny wrote:
>> Sorry I was not clear, I was speaking of the use of the VIA / CIA to
>> read the keyboard in  VIC20/C64
>> Apparently in the code I found  (code for C64) it is writing in the
>> row and reading the column
> I seem to remember that the VIC-20 is accessing the keyboard matrix in
> the opposite order.
> On a related note, some months ago I played with an Arduino Uno kit with
> my kids. The kit includes a 4×4 key matrix. And guess what, we got the
> same type of shadowing as on the C64 when multiple keys are pressed at
> the same time.

You want to get rid of shadowing and ghosting? Simple, use one 1N4148 
diode in series to each key. They keboard of my Amiga2000 used that 
trick back then and that solved the problem quite well.

For some reason it went out of style, probably the cost of the diodes.

Details see here:


       Message was sent through the cbm-hackers mailing list
Received on 2015-06-30 10:00:07

Archive generated by hypermail 2.2.0.