Keyboard Hack : problem with diodes

[VaRioR]

Hi !

I wanted to verify the effect of diodes on a keyboard hack to avoid ghosting and masking effects.

So I decided to choose 3 keys where the ghosting effect appears : A, Z and S (the S key didn't work).
I found the mounting sens of the diodes then I soldered beetween the two contacts of each key (it's an old keyboard with microswitches soldered on the main PCB) one diode and one pushbutton.

The test worked, but not in all orders...  
When I type A then Z then S : it works
But when I type A then S then Z, Z key isn't recognized  

I don't understand why this happens...

Could anyone help me solving that problem ?

ThanX

VaRioR.

[tmasman]

If you find a way around it, by all means share it with the community, but your best bet when hacking a keyboard is to just use a single row out of the matrix and not worry about diods and such.

In many cases it just isn't worth it.
I'm an advocate of hacking keyboards, but if you need more than 16 or so inputs for player controls, then you're better off either adding a hacked gamepad for one of the players, or getting yourself an encoder.