Re: reading vic20 or c64 column

I'm working on usb/bluetooth keyboard for several machines
I wanted to detect when the commodore is starting to scan the keyboard

1 usb keyboard or 1 windows application controlling a C64 or a tandy 
coco 1/2/3
the same board can fit a coco 3 or a C64  or VIC 20  (just different 
connectors)
the communication is done via serial bluetooth

a prototype works on a breadboard, I make a first PCB in a few days


On 30/06/2015 09:46, 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. And the characteristics differed, depending 
> on which way the rows and columns were connected to the ATmega328 pins.
>
> On a practical note, nowadays you would of course use a ‘commodity’ 
> input device for your DIY hardware, such as a USB or Bluetooth input 
> device or an infra-red remote control unit.
>
> Does anyone know about a semi-scientific writeup on keyboard matrices?
>
>     Marko
>
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