Author Topic: PC Engine 6-button Pad Schematic  (Read 9045 times)

Offline Lawrence

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PC Engine 6-button Pad Schematic
« on: July 02, 2009, 12:49:53 am »
I whipped this up today, after Gravis pointed out that I'd never actually done one before.

Please point out anything I may have missed, working this late into the night is not really conducive to error-free results.  =)


Click for full size
« Last Edit: July 02, 2009, 12:51:45 am by Lawrence »

Offline Lawrence

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Re: PC Engine 6-button Pad Schematic
« Reply #1 on: July 03, 2009, 10:09:52 am »
Schematic updated to version 1.1.  Now includes autofire circuit, proper chip designations (74LS157) and a correction to the connector pin names.

Offline Heffa

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Re: PC Engine 6-button Pad Schematic
« Reply #2 on: October 12, 2009, 10:12:45 pm »
Hey Lawrence - perhaps a stupid question, but what values does the resistor arrays have?  ???

Offline l_oliveira

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Re: PC Engine 6-button Pad Schematic
« Reply #3 on: October 12, 2009, 11:48:53 pm »
I'm not Lawrence, but I can safely inform you that 4k7 will suffice. :)
Since they're simply pull-ups, you can just use anything from 2k2 to 10k range.

Offline Heffa

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Re: PC Engine 6-button Pad Schematic
« Reply #4 on: October 13, 2009, 06:23:33 am »
I'm not Lawrence, but I can safely inform you that 4k7 will suffice. :)
Since they're simply pull-ups, you can just use anything from 2k2 to 10k range.

Thanks!  :)

Offline sonofx51

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Re: PC Engine 6-button Pad Schematic
« Reply #5 on: November 18, 2010, 04:09:40 pm »
sorry to dig up an old thread, but where would I put a toggle switch to select between 2 button mode and 6 button mode?

Offline Lawrence

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Re: PC Engine 6-button Pad Schematic
« Reply #6 on: November 18, 2010, 04:15:55 pm »
Pin 1 of the '157 chip closest to the connector. 

Your switch should connect it as shown OR connect it to GROUND.

Offline sonofx51

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Re: PC Engine 6-button Pad Schematic
« Reply #7 on: November 19, 2010, 05:29:11 am »
thank you.

Offline bigsanta

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Re: PC Engine 6-button Pad Schematic
« Reply #8 on: December 30, 2010, 02:11:09 pm »
I whipped this up today, after Gravis pointed out that I'd never actually done one before.

Please point out anything I may have missed, working this late into the night is not really conducive to error-free results.  =)

One detail i think will help out those making a demultiplexer circuit ,what is the clk speed that's used on the 74157's select pin ?Is it near what the mega drive's is for the 3 button pad about 60 hz or so ?

[EDIT by Lawrence: removed massive image in quote]
« Last Edit: January 04, 2011, 10:12:34 am by Lawrence »

Offline Lawrence

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Re: PC Engine 6-button Pad Schematic
« Reply #9 on: December 30, 2010, 02:25:10 pm »
I don't have any way to measure that, and I think it's software dependent.  If the game doesn't need an input, it doesn't have to ask.

I think 60Hz is a reasonable speed anyway, beyond that you won't have any effect on the game (since nothing can be seen more frequently than that) and slower could result in old/no input when it's required.   Try 120Hz to be safe, why not?  =D

EDIT: I have it on good authority that it IS software controlled but the standard is during vblank, so yeah, 60Hz.
« Last Edit: December 30, 2010, 02:27:11 pm by Lawrence »

Offline bigsanta

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Re: PC Engine 6-button Pad Schematic
« Reply #10 on: December 31, 2010, 01:52:45 am »
Great thanks ,now i'll just make up a 555 astable and see what we get when it's hooked up to a simple control interface like jamma.

Offline bigsanta

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Re: PC Engine 6-button Pad Schematic
« Reply #11 on: January 04, 2011, 03:29:34 am »
I whipped this up today, after Gravis pointed out that I'd never actually done one before.

Please point out anything I may have missed, working this late into the night is not really conducive to error-free results.  =)

Isn't it the RUN button ,not START ?!

[EDIT by Lawrence: removed massive image in quote]
« Last Edit: January 04, 2011, 10:12:49 am by Lawrence »

Offline bigsanta

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Re: PC Engine 6-button Pad Schematic
« Reply #12 on: January 04, 2011, 09:54:36 am »
Say we build this circuit and don't want the rapid fire part, the 74163,how will/can the third 74157 be connected to get its select signal ?

Offline Lawrence

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Re: PC Engine 6-button Pad Schematic
« Reply #13 on: January 04, 2011, 10:11:47 am »
You can't make this without the autofire chip, it's responsible for flicking back and forth between the two chips.  If you want to remove this chip you'll have to find something else to do the job.

That's probably why all the six-button pads had autofire - it's basically a free byproduct of the chip select mechanism. 

Offline bigsanta

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Re: PC Engine 6-button Pad Schematic
« Reply #14 on: January 05, 2011, 08:29:07 am »
I'm not Lawrence, but I can safely inform you that 4k7 will suffice. :)
Since they're simply pull-ups, you can just use anything from 2k2 to 10k range.
I'm looking at my avenue pad 6 pcb and it has the 330 ohms printed on the pcb (as in the schematic aswell) ,but for each pull up resistor on the buttons etc,those values are all printed  as 47k on the pcb .

Offline bigsanta

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Re: PC Engine 6-button Pad Schematic
« Reply #15 on: January 05, 2011, 08:31:46 am »
You can't make this without the autofire chip, it's responsible for flicking back and forth between the two chips.  If you want to remove this chip you'll have to find something else to do the job.

That's probably why all the six-button pads had autofire - it's basically a free byproduct of the chip select mechanism. 
Bummer,i'll just take that ic from an old core grafx pad then and stick the finished  circuit in my joystick .

Offline totoroslayer

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Re: PC Engine 6-button Pad Schematic
« Reply #16 on: February 19, 2017, 12:50:42 pm »
Just an FYI for those of you following along at home: the '157s and '163 all have Vcc and GND pins on each of the DIPs. Those have to be connected to 5v and GND, respectively (the schematic omits those for the sake of neatness).
« Last Edit: February 19, 2017, 01:36:57 pm by totoroslayer »

Offline totoroslayer

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Re: PC Engine 6-button Pad Schematic
« Reply #17 on: March 01, 2017, 06:00:12 pm »
Hi Lawrence,

Thanks again for the schematic.  I breadboarded this up and I'm running into a little glitch.  For ease of reading, I'll call the '157 that handles dpad, 1 and 2, run, and select as "mux1", the other '157 that handles 3,4,5,6 as "mux2."

First off, I have hooked up everything except the pins on mux 1 and 2 that correspond to the buttons, and the autofire pins on the '163 (those pins are just floating right now).  As well, I have hooked up all the Vccs and GNDs on all the '157s and the '163

I'm testing individual buttons right now, jumping a pin on the mux to a pull-up array, and then jumping that to ground to get my button press. Mux2 acts as mux 1 (i.e. 1B on mux2 gives me UP), and mux1 doesn't work at all.  If I disconnect Vcc on mux2, then mux1 works properly again (and as expected, mux2 won't work).  Any idea what's happening?  Are my breadboard connections failing?  Did you ever make a physical prototype and have pictures of it?

Thanks,
Myung

Offline Lawrence

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Re: PC Engine 6-button Pad Schematic
« Reply #18 on: March 03, 2017, 05:39:56 pm »
That's an interesting problem.  I can't see immediately why it would do this, except that...  Based on my quick reading of the datasheet, the 74157 doesn't have an internal pullup, so if you aren't giving it Vcc or GND on the inputs, it may be freaking out a little bit.  You may need to connect every button, either to your pullup resistor array or ground, before it behaves.

Offline totoroslayer

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Re: PC Engine 6-button Pad Schematic
« Reply #19 on: May 14, 2017, 04:59:45 pm »
Hi Lawrence,

So, an interesting development.  I laid out the PCB for these and got them prototyped. 



They seem to work fine (works nicely in the input tester and in Street Fighter II), EXCEPT when plugged in through a multitap.  When I do that, it thinks all the D-pad buttons are pressed, and shorting individual buttons to ground activates chords (i.e. 2 buttons at once). 



The normal Avenue Pad 6 doesn't seem to exhibit this behavior.  Any suggestions?

P.S. I added a switch that connects the Select line of the 3rd '157 (the one that feeds into the DIN 8 pins) either to ground (for 2 button mode) or into the '163's QA (for 6 button mode).

Thanks,
Myung
« Last Edit: May 14, 2017, 05:31:42 pm by totoroslayer »

Offline Lawrence

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Re: PC Engine 6-button Pad Schematic
« Reply #20 on: May 14, 2017, 10:19:17 pm »
OK, well you've sort of stumped me.  Obviously the multi-tap should work with the six button pad or we'd never have two-player Street Fighter.

If you're getting ULDR all at the same time, you're definitely getting a reading from the second '157 when the app expects the first.  I don't know what would cause this -only- via the multi-tap.  I assume the pad is in 6-button mode and you're reading it with a 6-button-aware soft, like Street Fighter, when this happens?


Offline totoroslayer

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Re: PC Engine 6-button Pad Schematic
« Reply #21 on: May 15, 2017, 01:26:52 pm »
Hi Lawrence,

I shot a quick video to give a little more context to the behavior:

https://www.youtube.com/watch?v=EG4YVa2SCjA

I took a look in side the Avenue Pad 6 and found a few caps across some lines, as well as what looks to be a transistor on the '163.  Could these function to stabilize or filter whatever is causing the malfunction?



-Myung
« Last Edit: May 15, 2017, 03:14:11 pm by totoroslayer »

Offline totoroslayer

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Re: PC Engine 6-button Pad Schematic
« Reply #22 on: May 20, 2017, 07:26:58 am »
Lawrence, would it help if I sent you the prototype board I made?


Offline Lawrence

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Re: PC Engine 6-button Pad Schematic
« Reply #23 on: May 21, 2017, 09:10:56 pm »
Sorry for the delay. I'm travelling overseas at the moment. I'll be back 6th June.

For sure I'm happy to check it out.  Maybe playing with it will give me some insights. I'll have to find my PCE multitap  tho. =)