In the warm glow of the MicroBasement, Jonathan A. Titus’s TRS-80 Interfacing Book 1 stands as a cornerstone for turning the TRS-80 from a game-playing appliance into a versatile hardware platform. Published in 1979 by Howard W. Sams & Co. (ISBN 0-672-21633-7), this 192-page paperback provided detailed, practical guidance on connecting the TRS-80 Model I to the outside world — sensors, relays, displays, printers, and more. It empowered hobbyists and experimenters to build custom interfaces using TTL logic, simple circuits, and assembly-language programming, proving the TRS-80 could be far more than a BASIC machine. In the MicroBasement collection, this book sits proudly beside early TRS-80 hardware and the Titus Mark-8 pages — a testament to how one clear guide could unlock real-world control for thousands of owners.
Jonathan A. Titus, the same designer behind the groundbreaking Mark-8 Minicomputer (from the July 1974 Radio-Electronics article), authored this book as part of the Blacksburg Continuing Education Series. Published by Howard W. Sams & Co. in 1979 (with some editions listed as 1980), it was aimed at TRS-80 owners eager to expand beyond cassette games and BASIC programs. Titus drew on his deep experience with microcomputer interfacing to create a practical, step-by-step resource that demystified the TRS-80's expansion bus and I/O capabilities.
The book is organized for hands-on builders. It begins with an overview of the TRS-80 Model I architecture: the Z-80 microprocessor, memory map, keyboard, video, cassette interface, and expansion port signals. Chapters cover decoding the address bus, using the expansion port for parallel I/O, building simple input/output ports with TTL latches and buffers (74LS series), handling interrupts, generating control signals, and interfacing to real-world devices like switches, LEDs, relays, stepper motors, analog-to-digital converters, and digital-to-analog converters. Later sections include timing considerations, power supply needs, breadboarding techniques, and assembly-language programming examples for controlling interfaces. The book includes full schematics, timing diagrams, parts lists, and code snippets — everything needed to build working projects.
Titus emphasized low-cost, reliable designs using common TTL ICs and minimal wiring. He explained how to safely access the TRS-80's expansion bus (avoiding damage to the machine), decode specific addresses for custom ports, and write Z-80 code to read/write data. Projects ranged from simple LED flashers and switch readers to more advanced ones like digital voltmeters, motor controllers, and data loggers. The book was forgiving for beginners while offering enough depth for experienced builders to create sophisticated peripherals, making the TRS-80 a true experimenter’s platform.
TRS-80 Interfacing Book 1 represents one of the critical turning points in the personal computing era. By giving TRS-80 owners complete blueprints for hardware expansion and real-world control, Jonathan A. Titus turned a popular home computer into a versatile laboratory tool for education, automation, and invention. It inspired countless custom projects, from home security systems to scientific instruments, and helped prove that affordable microcomputers could handle serious interfacing tasks. Preserving and demonstrating this book is essential because it embodies the foundational efforts of engineers and authors who created the pathways for modern embedded systems and IoT. In the MicroBasement, its pages rest beside TRS-80 hardware, the Mark-8 replica, and other Titus works — a quiet reminder that one well-written book can transform a game machine into a gateway for real-world creativity and discovery.