A-ONE I/O Interface

A-ONE I/O Interface Board

8-Bit Input / Output Expansion for the A-ONE Apple-1 Replica

Expand your A-ONE system with real hardware interaction.

The A-ONE I/O Interface Board is a practical 8-bit input and output expansion card designed for the A-ONE Apple-1 replica platform. It allows users to directly read digital inputs and control external outputs from BASIC or machine code, making it perfect for retro-computing experiments, education, and hardware prototyping.

The board features a clear and intuitive layout with:

• 8 red LED indicators for output monitoring
• 8-position DIP switch input bank
• Selectable I/O addresses via jumpers
• Direct A-ONE bus connection
• Ready-to-use visual input/output testing platform

Ideal for learning how early microcomputers interacted with the outside world.

Key Features

• 8-bit output port (D0–D7)
  The 8 LEDs provide instant visual feedback of the output byte written by the system.
• 8-bit input port
  The onboard DIP switch allows manual input of values from 0 to 255.

• Address selectable

  Easily configurable through jumpers:

  • A000
  • A100
  • A200
  • A300
• Perfect for BASIC experiments
  Read and write bytes directly from Apple-1 BASIC.
• Educational hardware interface
  Excellent for demonstrating memory-mapped I/O, binary logic, and low-level programming.

How It Works

The A-ONE I/O board uses memory-mapped I/O, just like classic 1970s computer hardware.

The DIP switch provides an 8-bit binary input value, while the LED row shows the 8-bit output value written by the computer.

For example in BASIC:

A = 128
POKE -24576, A

This writes the value to the output port and lights the corresponding LEDs.

To read the switch settings:

B = PEEK(-24576)
PRINT B

This makes it a fantastic tool for learning how vintage computers communicated with real-world hardware.

Perfect For

• Retro computing enthusiasts
• Apple-1 / A-ONE collectors
• Educational demonstrations
• Binary and logic experiments
• BASIC programming projects
• Hardware interfacing

What’s Included

• 1x A-ONE I/O Interface Board
• Fully assembled and tested
• Ready for direct use with your A-ONE system

Disclaimer

A-ONE is a modern replica system inspired by the 1976 Apple-1 computer. This product is not an original Apple product and is not affiliated with, endorsed by, or associated with Apple Inc. The name Apple-1 is used strictly as a historical reference for compatibility and educational purposes.