Posted by matt(v) on July 16, 1999 at 21:47:27:
In Reply to: Ghosting. Whats the bottom line? posted by Jim M on July 16, 1999 at 18:52:34:
: Does the keyboard hack with diodes eliminate the ghosting problem? It has not for me so for when I testing. But I think I'm using the wrong diodes So I'm getting different ones tonight.
: Jim M
Does a keyboard hack with diodes eliminate ghosting? Well that depends. Before I say anything else I should point out that it is possible to have approximately 20 simultaneous inputs on a keyboard hack without ghosting using NO diodes at all.
I say approximately 20 because this depends mainly on the exact keyboard you use. Keyboards use a matrix system to keep track of keypresses and when you overload this matrix you get a "ghost" (or a jam). So what to watch out for?
All the keyboards I have seen use a 20 by 7 (or so) matrix for the keys, you could lay this out on a table and read off the table which key will be cativated when a certain row and column are activated. If you did this you would see that once three keys that form 3 corners of a rectangle are activated, the key at the other corner of the rectangle is accidently activated as well, this is a ghost.
So how to get around this? Well as I said before most matrix are 20 columns by 7 rows, so if you only used one key in each column you would never get a jam (you also end up with some pretty damn weird control setups) You can get a few more "non ghosting" inpust by putting conrtols that you KNOW will never pe used at the same time on the same column (player one up/down for example).
I hope this helps but I fear that without a better knowledge of how keyboards work you won't understand (it took me long enough) if you need further explaination juts let me know.
Matt(v)