Simple Atari-Style Joystick to Creativision adaptor

[kevgal]

How about using a Sega Mega Drive controller? Plenty of cheap ones on Ebay, take advantage of the fact that the second fire button and keyboard buttons are on the other strobe line?

[Mobsie]

Yes they are one of the best controller. Also i like the original NES Controller

[kevgal]

This might work?

[Scouter3d]

This might work?

Hi, it looks plausible...

PS: if this should be external the diodes need to be schottky diodes (with a low voltage-drop)... like in Chesh´s keypad-replacement

Cheers, TOM:0)

[kevgal]

Here is a working Genesis game pad to CV adapter. It was a little more complex than I anticipated due to a few issues.
There is a lag in the falling edge of the keyboard strobe that runs into the Joystick strobe (possibly due to the filter caps on the inputs of the model I am using). This would not normally be a problem as one would not usually be pressing a keyboard button while using the joystick, however Sega in their infinite wisdom decide to pass the Left and Right controls through the same IC as the buttons and then ground the unused inputs. This has the effect of holding the left and right control down during the small window of overlap of the strobes. This was causing all sorts of weird effects (it doesn’t help that the CV's PIA is a part time sound generator).
The best solution was to invert the Joystick strobe and use that as the select line which also cleaned up the pulse a bit. The joystick strobe also happens just after the keyboard strobe so the long run off doesn't effect anything (except for the diagnostic program in which case the joystick strobe happens before and during the keyboard strobe which was very confusing!).
Having sorted that out it came down to what to do with button 'C'.
This is active during the Joystick strobe but there is only the ‘A’ button used by the CV during this period. To use the 'C' button it needed to be delayed long enough to hit the Keyboard strobe which required a simple sample and hold circuit (a lot of trouble to go to just to be able to drop mines in Tank Attack!).
Since my circuit is 'built in' also requires some pull up resistors and extra diodes so as not to interfere with the CV controller when the gamepad is not connected.
Some images attached.

[Scouter3d]

Hi Kevgal,

great work! I will have to sit down with a good glass of wine and study your design :0)

PS: I love the "GERANIUM" diodes ;0)

Cheers, TOM:0)

[kevgal]

Flower power!

[Mobsie]

That’s Amazing cool.

[cheshirenoir]

Cool! Good to see all these new projects coming on board.

John

[kevgal]

Just did some tests on the commercial games to determine what buttons do what-
All games start with any button other than the column with 1, CNTL, <- , and SHIFT.
All games use both fire buttons, CNTL and SHIFT (which are the same as the fire buttons any way) to select different modes.
All games use both fire buttons as action buttons .
No game uses 1 or <- for anything in game.

These games are slightly different-

Pinball –
Both paddles cannot be used at the same time. The left paddle takes precedence.
Any button (other than the first column) can be used to release the ball.

Chopper rescue-
Has no mode select

Tank Attack-
Lay Mine keys - 2,3,Q,W,A,S,Z,X
Swap Tank keys - 4,5,6,E,R,T,D,F,G,C,V,B.