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The Opti-PAC (Optical Interface for Pc to Arcade Controls) is an interface for easily connecting optical-type arcade control devices including trackballs and spinners to a PC for use with emulators such as MAME.

The Opti-PAC. Click for a Hi res pic.

Features:
  • USB Mode: One USB cable handles up to two trackballs and 4 spinners/rotary joysticks.
  • Serial mode: Two independent serial port inputs to accomodate two trackballs and 4 spinners/rotary joysticks.
  • No external power needed when used in USB mode.
  • In serial mode takes power from I-PAC using supplied cable, or any 5V source.
  • The active control (trackball or rotary) is automatically selected using a "first moved" method.
  • Supports buffered controls (Happ type) or unbuffered (Suzo, Wico), high or low polarity.
  • Configurable via software, jumpers, or external switch for the following modes.
  • USB Interface:
    • Works in one or two player modes (one USB mouse device) in Windows. Auto-switching between trackball and spinner
    • Also works in two player mode (two USB mouse devices) using recent MAME versions which support independent mouse devices (ie 2 trackballs).
    • Will work alongside PS/2 or USB mouse if required.
  • SERIAL interface:
    • DUAL SERIAL MODE: 2 Player, 2 trackball or 2/4 spinners. Independent control for each player.
    • AUTO-SWITCH MODE: Auto-switching between trackball and spinner into one serial port.
    • SOFT-SWITCH MODE: Software switching via mouse driver to select trackball or spinner as required.
    • HARDWARE SWITCH MODE: External switching between trackball or spinner into one or two serial ports.
    • Will work alongside PS/2 or USB mouse if required.

      The I-PAC and Opti-PAC. Click for a Hi res pic.

      Technical Info:
      A one-axis optical control such as a spinner has one LED which shines across a spoked wheel onto two sensors.
      The two sensor outputs are compared with each other to generate movement direction.

      Therefore the interface requires two parts:
      A voltage supply for the LED.
      Inputs for the two sensors.
      The OPTI-PAC has outputs for the LED and the 2 inputs for the two sensors. It takes all voltage needed from the USB port when used in USB mode.

      A dual-axis device such as a trackball has all the above multiplied by two. Two LEDs, two pairs of sensors. So the board has two independent circuits for the X and Y directions. These two circuits can either be used on the same dual-axis device or separate single-axis spinners.
      Testing: Opti-Pac, I-PAC, Cypress microcontroller development board
      2 Suzo and 1 Happ Trackball Click for a Hi res pic.