TRS80 Model I Arduino Mega Shield

TRS-80 Model I Arduino Library

NOTE: There are still a lot of changes that are happening within this library. Use this only for testing. We will make breaking changes. A stable version will be released shortly before TA 2025.

Arduino library for interfacing with TRS-80 Model I hardware via the 40-pin edge connector. Control memory, video, keyboard, and bus signals to create ROM dumpers, RAM testers, and custom peripherals.

Hardware Required: Arduino Mega 2560 (only board with sufficient GPIO pins)

Quick Start

Basic Usage

#include <M1Shield.h>
#include <Display_ST7789_320x240.h>  // Choose your display

Display_ST7789_320x240 displayProvider;

void setup() {
    M1Shield.begin(displayProvider);
}

void loop() {
    M1Shield.loop();
}

Read & Write

#include <Model1.h>

void setup() {
    Model1.begin();
    Model1.activateTestSignal();

    uint8_t data = Model1.readMemory(0x0000);  // Read ROM
    Model1.writeMemory(0x3C00, 0x41);          // Write to video RAM

    Model1.deactivateTestSignal();
}

UI Framework with String Support

#include <ContentScreen.h>

class MyScreen : public ContentScreen {
public:
    MyScreen() {
        // Three ways to set titles/text - choose what fits your needs:
        setTitle("Static Title");                    // Simple C-string
        setTitle(String("Score: ") + String(score)); // Dynamic Arduino String
        setTitleF(F("Memory Efficient"));            // Flash string (F-macro)
    }

protected:
    void _drawContent() override {
        // Draw dynamic content easily
        String playerName = "Alice";
        drawText(10, 10, String("Player: ") + playerName, WHITE);
        drawTextF(10, 30, F("Static text"), YELLOW);  // Saves RAM
    }
};

Key Features

• Complete TRS-80 Bus Control - Read/write memory, control signals, interrupts
• High-Level Classes - Model1, Video, Keyboard, ROM, Cassette for easy access
• Low-Level Access - Model1LowLevel for advanced users requiring precise control
• M1Shield Support - Hardware abstraction for Arduino shield with display/input
• UI Framework - Screen management system for building interactive applications
• Flexible String Support - All text functions support C-strings, Arduino Strings, and F-strings
• Multiple Display Support - ST7789, ILI9341, ST7796, SSD1306, and more
• Arduino Compatible - Standard Print interface, familiar patterns

Installation

1. Install via Arduino Library Manager or download from GitHub
2. Connect Arduino Mega 2560 to TRS-80 (M1Shield recommended, direct wiring supported)
3. Try examples: M1Shield/SimpleM1Shield or Model1/Model1/SimpleModel1

Examples

Complete Examples Guide - Comprehensive examples with progressive learning paths

The examples folder contains over 40 examples organized by functionality:

• M1Shield Examples - Hardware platform and display examples
• Model1 Examples - TRS-80 hardware interface (ROM, RAM, Video, Keyboard, etc.)
• UI Examples - User interface framework and screen management
• Logger Examples - Debugging and monitoring system

All examples follow a Simple/Comprehensive pattern for progressive learning, with complete documentation and integration guidance.

Connection Options

M1Shield (Recommended): Clean, safe connection with built-in display and controls
Direct Wiring: Connect via jumper wires using our pin mapping guide

WARNING: See TEST Signal Fix for hardware reliability improvement

Documentation

Complete Documentation - Detailed API reference and guides

Main TRS-80 Model 1 Repository

For additional resources related to the TRS-80 Model 1, be sure to check out the central page for the TRS-80 Model 1 on RetroStack.

Support this Project

RetroStack is passionate about exploring and preserving the legacy of older computer systems. My work involves creating detailed documentation and videos to share the knowledge. I am also dedicated to reviving these classic systems by reimplementing them and offering replacement parts at no cost. If you're keen on supporting this unique project, I invite you to visit my Patreon page. Your support would be immensely valuable and greatly appreciated!

License

This project is licensed under the MIT License - see the LICENSE file for details.