PSX Ctrl Adapter for Vectrex


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IMPORTANT NOTE: Clay Cowgill was selling a premaid adapter years ago, that didn't require you to dedicate a psx controller. I don't know how easy it would be to track down (but the furniture pic in the misc section is worth a click): multigame.com

I picked up a Veccy at the CGE2k3 auction, got it home and jumped on the internet that night. Within half an hour, I'd thought up this circuit, then half an hour after that, found Clay's website (major bummer). Still went ahead and built it because I haven't had a chance to play with op-amps in quite awhile. Besides, an off-the-shelf solution with <$10 in parts is interesting in its own right and it's fully analog, unlike genesis adapters. BTW, this is a 5-7 hour project.


vectrex psx adapter

Genesis extension cable, project box, psx dual shock

 
PARTS LIST:

LM324 quad low-power op-amp
100k resistors (x8)
1k pots (x4)
diodes, silicon or schottky fine (x5)
100uf electrolytic cap (10uf also ok)
psx analog controller
cutoff genesis controller cable (or genesis extension cable
 and female dsub9 connector) 
project board
project box


SCHEMATIC:

       5v        5v          5v
       |          \           \
       | 100uf    /           /
      ___         \<<--2v(a)  \<<--2v(b)
      ___         /           /
       |          \ P1        \ P2
       |          /           /
      -5v        gnd         gnd


   psx_button_1---------|<----------vec_button_1 
   psx_button_2---------|<----------vec_button_2 
   psx_button_3---------|<----------vec_button_3 
   psx_button_4---------|<----------vec_button_4 
   psx_red_wire---------|<----------vectrec_5v_pin 
   psx_black_wire-------------------vectrex_ground

 ,___________________________________________,
 |                                           |
 |               vec_hor                     |
 |                  |      +---+--+---+      |
 |           ,__P4b_|_1OUT |1  +--+ 14| 4OUT_|__R__,
 |  gnd__P4a_|________-1In |2       13| -4In_______|____R___2v(a)
 |____________________+1In |3       12| +4In____________R___gnd
                  5v___VCC |4 LM324 11| VEE___-5v  |____R___psx-b  ,__R__psx-a
                 gnd__+2In |5 OP421 10| +3In_______________________|
             ,________-2In |6        9| -3In____________R___2v(b)  |__R__gnd
  _______P3a_|__P3b___2OUT |7        8| 3OUT____R__|                  
 |                  |      +----------+      |
 |                  |                        |
 |               vec_vert                    |
 |                                           |
 |___________________________________________|

NOTE: Cleaner op-amp schematics are at bottom of page.
      You get a gold star if you can figure out the circuit from just this
      wiring diagram :)  

psx veccy mod 2

Inner circuits, not a whole lot there (buttons were wired up later)

You can see I sometimes get lazy and use scotch tape instead of shrink tubing

HOW IT WORKS:

The vectrex 5v supply is dropped by a diode to 4.2v, which is close
to the normal psx supply,  so the controller just sits there
powered up with no playstation to communicate with.

The 4 psx face buttons are tied to the 4 vectrex buttons, the
diodes keep the psx controller from pulling the signal up itself.
This is the button arrangement I like:      2 
                                          1   3
                                            4

The psx analog stick has a horizontal signal that goes from
0v (west) to 2v (middle) to 3.8v (east).  The first op-amp
subtracts 2v from the signal so it is centered around 0v.  The
second op-amp is a noninverting amplifier which increases the
signal to about -3.5v (west), 0v (middle), 3v (east).  

This is close to what a vectrex controller pot itself does.
The psx pad is not completely symmetric around the midpoint 
which would have been nice, but things still work.  My vectrex
had different voltages than the specs anyway, so there was some
room for slop designed in.  

The vertical signal is handled the same way, except it goes
through an inverting amplifier because the psx and veccy use
opposite orientations. 


ASSEMBLY INSTRUCTIONS

Deathskull Labs Archive has Vectrex pinouts and controller theory.

I couldn't recall if the ps2 controller buttons are purely digital,
so just stuck with the official Sony psx version.  Too bad they
aren't black, but they are cheap, $15 or less.

The psx-a and psx-b pot signals are found on the back of the
controller board as shown.  The four button signals are found
on the front side.  I used 30-guage wire so it wouldn't lift
up the rubber base thingee too much.  


                                     ,_____ leave red(vcc),black(gnd);
                                     |      lift the others
                                     v
                   __----__________________________----__
                  /               xxxxxxxx               \
                 /                                        \
                /                                          \                                           
                |                                          |
                |                                          |
                |      Right stick       Left stick        |
                |           x                x             |
               /          x   x            x   A            \
               |            x                B              |
              /        _____________________________         \
             (        /                             \         )
             \       /                               \       /
              \_____/                                 \_____/
                     NOTE: back-side of controller board


You have 8 signals (vcc,gnd,2 pot lines, 4 bottons) so you can
just use the original psx cable.  Just leave the vcc and gnd
wires on the board, and lift up the other six for your connections. 

Be VERY CAREFUL about double checking things.  A Vectrex is too
special to destroy by having the incorrect wiring.  I rigged up
a +/- 5v supply with a dsub9 jack and verified everything before
plugging the adapter into an actual veccy.  

Hook up the psx controller, leave the stick neutral, and dial the
2v pots until the first stage op-amps go to 0v output (it should be
at about 2v input).  The 1k pots are two orders of magnitude below
the 100k op-amp subtractors and shouldn't be affected by them.

Then dial the other two pots until the op-amp voltages at the most
extreme positions (hard west or hard east,  hard north or hard south) 
are up to +/-3.5v.  The other one of the pair probably won't be as
high, but don't worry about it.  The pots are actually changing the
amplifier gain.       

The genesis plug will need some nibbling on the sides to plug into
the veccy jack.  



OP-AMP DIAGRAM
                                                       
Horizontal Circuit (op-amp subtractor plus noninverting amp)

        
                   100k                     100k
       2v(a)------/\/\/----+---------------/\/\/------,
                           |                          |
                           |     |\                   |
                           |     | \     5v           |
                           |     |  \  -----          |
                           |     |   \   |            |
                           |     |    \ _|            |
                           '-----|-    \              |
                                 |      \             | 
                                 | LM324 \____________|______   
                                 |       /                   |
                                 |      /                    |
                           ,-----|+    /                     |
                           |     |    /--,                   |
                           |     |   /   |                   |
                           |     |  /  -----                 |
                           |     | /    -5v                  |
                           |     |/                          |
         psx               |                          |      |
         hor------/\/\/----+---------------/\/\/------|gnd   |
                  100k                      100k      |      |
                                                             |
                                                             |
      ,------------------------------------------------------'
      | 
      | 
      |      |           Pot4                    
      |   gnd|---------/\/\/\/\/----------------------,
      |      |             |                          |
      |                    |     |\                   |
      |                    |     | \     5v           |
      |                    |     |  \  -----          |
      |                    |     |   \   |            |
      |                    |     |    \ _|            |
      |                    '-----|-    \              |
      |                          |      \             | 
      |                          | LM324 \____________|______ to
      |                          |       /                vectrex hor
      |                          |      /                 
      ---------------------------|+    /  
                                 |    /--,
                                 |   /   |
                                 |  /  -----
                                 | /    -5v
                                 |/
                                                       


Vertical Circuit (op-amp subtractor plus inverting amp)

        
                   100k                     100k
       2v(b)------/\/\/----+---------------/\/\/------,
                           |                          |
                           |     |\                   |
                           |     | \     5v           |
                           |     |  \  -----          |
                           |     |   \   |            |
                           |     |    \ _|            |
                           '-----|-    \              |
                                 |      \             | 
                                 | LM324 \____________|______   
                                 |       /                   |
                                 |      /                    |
                           ,-----|+    /                     |
                           |     |    /--,                   |
                           |     |   /   |                   |
                           |     |  /  -----                 |
                           |     | /    -5v                  |
                           |     |/                          |
         psx               |                          |      |
        vert------/\/\/----+---------------/\/\/------|gnd   |
                  100k                      100k      |      |
                                                             |
                                                             |
      ,------------------------------------------------------'
      | 
      | 
      |                  Pot3
      `----------------/\/\/\/------------------------,
                           |                          |
                           |     |\                   |
                           |     | \     5v           |
                           |     |  \  -----          |
                           |     |   \   |            |
                           |     |    \ _|            |
                           '-----|-    \              |
                                 |      \             | 
                                 | LM324 \____________|______ to 
                                 |       /                vectrex 
             |                   |      /                 vertical
          gnd|-------------------|+    /  
             |                   |    /--,
                                 |   /   |
                                 |  /  -----
                                 | /    -5v
                                 |/
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