Posted by Tiger-Heli on 14, 2001 at 6:26 AM:
In Reply to: keyboard hack questions posted by dan on 13, 2001 at 10:44 PM:
First see my page at http://www.mameworld.net/emuadvice/keyhack2.html (Link below)
: I now read all I can find on keyboard ghosting and how to prevent it, but still have a number of questions:
: 1) various sites mention that a keyboard IC usually has 8 'y' and 13 'x', or 12 and 12, etc. How can I determine how many mine has - mine has a big chip on the top with various electronically diodes (I think), and then tons of green lines on the back side with pins on the ends of each green line.
There should be approximately 24 terminals on the IC. You need to check each key and map out which terminal each key is going to. The linked page covers this extensively.
: 2) I plan on geting diodes to prevent ghosting; will this also allow multiple keys to be pressed and the IC recognizing them? I plan on a 4 player with 6 buttons each, plus 6 MAME keys, for a total of 46 keys.
Probably not, as I mention on the linked page, the more common problem is not ghosting, but blocking. Use one of the keypress registering tools on this site. If you can get more than 16 simultaneous keypresses to register, you might get by with diodes.
With that many inputs, though, you will be much better with a commercial encoder. (daisy-chained I-PACS, MK64, Hagstrom, etc.)