PC-FX controller interface

[mojo]

Hi. I am working on a project to connect a microcontroller to a PC-FX pad, and then to USB. I am having trouble finding detailed info on the pad.

So far I have managed to glean some info from a few Japanese web sites. It appears to be a parallel in serial out shift register arrangement, similar to Famicom/NES/SNES pads. The problem is figuring out which lines do which.

There are four "data" lines. One must be latch, one serial data and one serial clock. I think the forth is a read/write toggle, but I'm not sure what you would want to actually write to the controller. Might be something to do with multi-taps.

Has anyone got any more information? I will figure it out by simply trying all possibly combinations of lines eventually, but it would be a lot easier if someone could provide even just a pin-out.

I've spent ages looking for developer docs but can't find any online :(

[Calpis]

Have you tried opening up the controller? I would have guessed it was based on the PCE pad.

[mojo]

I have opened it, but it is different to the PC-E pads.

Inside there is one IC, a custom NEC one which I cannot find a data sheet for. I was at least able to get the pinout for the cable:

1. 5V
2. D0
3. D1
4. D2
5. GND
6. D3
7. GND

The documentation says it is a serial interface.

[Calpis]

Do you have a multimeter with frequency counter? Load will be 60ish Hz, CLK will be 60ish*12ish Hz, Data will be a very low frequency without pressing any buttons, slightly higher by pressing some of them. If you think one signal is a data input, it will be DC.

[mojo]

I have a logic analyzer, what I don't have is an actual PC-FX console to connect my controller to >_<

If I had one I could figure it out in minutes. Maybe I'll have to look at getting one, but outside of Japan they sell for silly money.

[Calpis]

Do you have a PC with parallel port? You could connect all 4 signals to the data port through 4.7K resistors and feed them back to the status port.

[mojo]

Do you have a PC with parallel port? You could connect all 4 signals to the data port through 4.7K resistors and feed them back to the status port.

Sorry, I don't follow you... I don't have an actual PC-FX console, only the controller. I have a logic analyser so reading the data isn't a problem.

[Calpis]

Without the console you could RE the controller just using a parallel port. The resistors will protect the LPT and pad during conflicts yet still drive the pad's inputs and yield to the pad's output.

http://img26.imageshack.us/img26/2317/pcfxpadre.jpg

Reading the protocol with your logic analyzer *is* a problem if you don't have a console ;)

[mojo]

Ah, I see what you mean. I can just use the AVR to do that though, it's easy enough. You have given me an interesting idea though - a debug lead using USB and an AVR with a Windows program to control the I/O lines.