Plus4 Mouse Project

Commodore Plus/4 is still a very universal computer what you can also use with a mouse like you do with Commodore 64 and many others.

The Plus4 Mouse Project was originally created by Szilveszter Bencsik, who published it as open source on GitLab. 🎓

🖱️ Project Goal

• To create a mouse driver for the Commodore Plus/4 that supports various mouse types and integrates with BAIC BASIC extensions.

⚙️ Supported Mouse Types

• RS-232 serial mouse (2-button)
• 1351 mouse via SIDcard
• Amiga mouse in digital mode via BSZ audio extension
  • Atari mice may work too, if switched properly before using BASIC.

🛠️ Development and Usage

• Recommended development tool: CBM PRG Studio
• Documentation and examples: plus4 mouse handling PC ACIA MOUSE SID CARD MOUSE PDF

💾 Memory Addresses and Pointers

• The code defines memory addresses for retrieving mouse coordinates and button states from BASIC or custom programs.
• Examples:
  • .MerX = $0421 → X coordinate
  • .Rs2Btn = $0426 → RS-232 button state

🔧 Hardware Considerations

• Serial mouse: easy to obtain and affordable.
• SID card: more expensive but already available for many users.
• Amiga mouse: harder to get — a USB → Amiga adapter (like a wireless light mouse) is recommended.
• PS/2 → Amiga adapters do not work — avoid ordering those.

🧩 Future Plans

• The driver will automatically load into upper memory to preserve BASIC area.
• Possible OS expansion through EPROM.