Great Hierophant
Veteran Member
Most games that are "Apple IIe aware" use the cursor keys for movement. Interestingly, the Apple IIe has a numeric keypad connector which provides the X/Y output/input lines for a keypad. This allows you to use any passive keyboard matrix as a keypad.
The numeric keypad connector does not bring out all X and Y lines, it brings out X4-X7 and Y0-Y5. What any combination of X and Y are is defined by the keyboard decoder ROM, a simple 2KiB chip with EPROM compatible pinouts. The AY-3600 Keyboard Decoder reads this ROM to determine which ASCII to send when a key is pressed.
Fortunately, with Keyboard ROM 341-0123-C or D, the cursor keys are mapped to the matrix that the numeric keypad uses. Y1 + X4 is down, Y1 + X5 is Up, Y1 + X6 is Left and Y1 + X7 is Right. Map those appropriately to a digital joystick (Y1 is the common) and there you have a digital joystick.
But what about buttons? Well, PB0 and PB1 are typically used as buttons and connections for those are available on the Game I/O connector. One thing to be aware of is that the button inputs connect to +5v, but they do not need pulldown resistors as in an Apple II or II+.
So it is quite possible to make an Apple IIe Joystick that has digital inputs. Of course as contemplated this is the only Apple II system in which this idea will work.
I have attached a file showing what modifications would need to be made to something common like an NES gamepad which would be needed to get a gamepad working. The PCB must be stripped of its chip and any passives without destroying the holes in the process. I would suggest using a DE-9 cable and soldering the wires on one end to the PCB as shown. The cable can plug into a mated DE-9 connector mounted on the IIe's rear and from there the other ends would connect to their appropriate pins.
The numeric keypad connector does not bring out all X and Y lines, it brings out X4-X7 and Y0-Y5. What any combination of X and Y are is defined by the keyboard decoder ROM, a simple 2KiB chip with EPROM compatible pinouts. The AY-3600 Keyboard Decoder reads this ROM to determine which ASCII to send when a key is pressed.
Fortunately, with Keyboard ROM 341-0123-C or D, the cursor keys are mapped to the matrix that the numeric keypad uses. Y1 + X4 is down, Y1 + X5 is Up, Y1 + X6 is Left and Y1 + X7 is Right. Map those appropriately to a digital joystick (Y1 is the common) and there you have a digital joystick.
But what about buttons? Well, PB0 and PB1 are typically used as buttons and connections for those are available on the Game I/O connector. One thing to be aware of is that the button inputs connect to +5v, but they do not need pulldown resistors as in an Apple II or II+.
So it is quite possible to make an Apple IIe Joystick that has digital inputs. Of course as contemplated this is the only Apple II system in which this idea will work.
I have attached a file showing what modifications would need to be made to something common like an NES gamepad which would be needed to get a gamepad working. The PCB must be stripped of its chip and any passives without destroying the holes in the process. I would suggest using a DE-9 cable and soldering the wires on one end to the PCB as shown. The cable can plug into a mated DE-9 connector mounted on the IIe's rear and from there the other ends would connect to their appropriate pins.
