Enhanced Dual Joystick for RC2014

Add-on board designed for the RC2014 computer to provide an enhanced dual joystick port for games and other applications.

The board is based on a Z80 PIO that provide two 8-bit bi-direction parallel ports. Software can configure each port independently to use a standard Atari-compatibile joystick, a NES-compatible gamepad or any other controller driven by digital I/O lines.

I/O ports can be configured with the on-board dip-switch.

Schematics

Parts List
R1	10.000 ohm 1/4 watt
RN1, RN2	10.000 ohm, 9-pin resistor network
RN3	10.000 ohm, 7-pin resistor network
C1, C2	100.000 pF polyester
IC1	Z84C2010PEG
IC2	CD74HCT688N
S1	DIP-switch
CN1	40 pin male header, right angle
CN2, CN3	DB9 male connector

Additionally, a NES-compatible gamepad board is included for those who don't have access to an existing joystick.

Parts List
R1-R8	10.000 ohm 1/4 watt
C1	100.000 pF polyester
IC1	CD4021
UP, DOWN, LEFT, RIGHT	6x6 mm tact switches
SELECT, START, B, A	6x6 mm tact switches
CN1	5-pin connector

Code Examples

The Z80 PIO must be initialized at startup by configuring both ports in control mode 3 followed by the pin direction settings appropriate for the game controller type.

Atari 2600 joystick.

PIO_BASE    .EQU    70H

            ; initialize

            LD      A,0CFH              ; set port A mode 3 (control)
            OUT     (PIO_BASE+1),A
            LD      A,0FFH              ; all pins as input
            OUT     (PIO_BASE+1),A

            LD      A,0CFH              ; set port B mode 3 (control)
            OUT     (PIO_BASE+3),A
            LD      A,0FFH              ; all pins as input
            OUT     (PIO_BASE+3),A

            ; read joystick 1

            IN      A,(PIO_BASE)

            ; read joystick 2

            IN      A,(PIO_BASE+2)

NES gamepad on Joystick 2.

The code assumes that the gamepad is wired to the DB9 connector as follows: 4=data, 5=load, 6=clk.

PIO_BASE    .EQU    70H

NES_LOAD    .EQU    20H
NES_CLK     .EQU    10H

            ; initialize

            LD      A,0CFH              ; set port A mode 3 (control)
            OUT     (PIO_BASE+1),A
            LD      A,0FFH              ; all pins as input
            OUT     (PIO_BASE+1),A

            LD      A,0CFH              ; set port B mode 3 (control)
            OUT     (PIO_BASE+3),A
            LD      A,~(NES_LOAD|NES_CLK)   ; clock and load pins as output, others as input
            OUT     (PIO_BASE+3),A
            LD      A,0
            OUT     (PIO_BASE+2),A

            ; read joystick 1

            IN      A,(PIO_BASE)

            ; read joystick 2

            LD      C,0

            LD      A,NES_LOAD          ; pulse load pin
            OUT     ((PIO_BASE+2),A
            LD      A,0
            OUT     (PIO_BASE+2),A

            LD      B,8
L1:         IN      A,(PIO_BASE+2)      ; read data from bit 0
            RRA
            RL      C

            LD      A,NES_CLOCK         ; pulse clock
            OUT     (PIO_BASE+2),A
            LD      A,0
            OUT     (PIO_BASE+2),A

            DJNZ    L1

            LD      A,C

Boards

Boards are shared on OSHPark:

Dual Joystick
Game Controller

A donation to support this and future projects is always welcome!