Posted by Druin on 23, 2001 at 2:44 AM:
In Reply to: Nes gamepad posted by gunne on 21, 2001 at 11:31 AM:
I knew I had come across a circuit before so I just went through my pile of magazines.
Popular Electronics, December 1993 is where I found it. "NinJA-15 by Larry L. Cameron" designed to convert the 8 bit NES gamepad to 8 switches which can be of course used to connect to a keyboard encoder, but back in 93 I guess they didn't have that in mind...
The schematic uses the following chips:
74HC190 counter/divider
74HC595 latched shift register
555 timer
and the rest is trivial...so it should be commonly available parts.
Too bad my scanner is currently out on loan but eventually I could give better insight about the circuit. Just for fun, here's some of the writeup:
The Nes gamepad has a 4021 parallel in - serial out shift register. There are 8 switches on the gamepad, which are the 8 parallel inputs (pulled high), and the nintendo control deck provides a clock signal for the 4021 to send out the switch status.
The 8 joystick switches are read, then the readings are sent out one by one serially, so the circuit in the article is a backwards serial to parallel converter to decode the data and expand it back into 8 switches, which we can then throw on a keyboard encoder.