Binary keypad front panel

[John Wilson]

I made this as a joke, but also as a simple test device for a NatInst
PCI-DIO-96 GPIO card I was writing a driver for:

	https://www.facebook.com/john.m.b.wilson/videos/10212562451077947/

It occurred to me that lots of old machines had binary front panels
(switches and lights) and lots of machines had keypad front panels (octal
or hex, with 7-segment LEDs), but I'd never seen a binary keypad front
panel.  Plus I wanted to experiment with Cherry MX keyswitches, and try out
wasdkeyboards's custom keycaps (but they're $7/ea so I didn't want to try
anything too big the first time).  That plus two 74LS132s, four 74LS240s,
and two 74LS273s, discrete stuff and cabling, and a PCI-DIO-96 that was
$25 on eBay, and it works.

"set dr dio96:" in the DOS and stand-alone versions of E11 V7.3 makes it
(or anyone else's homemade doohicky) appear at 777570 as usual (or you can
add "set dr r0" to get the R0-during-WAIT display like on a PDP-11/70 --
whatever your OS's NULJOB uses).  I'd give Gerbers to anyone who cares
but really it's just a dumb joke.  Fun one though.

John Wilson
D Bit