Tito Figueiredo's Breadboard Build Turns a Vintage Zilog Z80 Into a Microcontroller

Electronics hobbyist and motorbike mechanic Tito Figueiredo has put together a somewhat less-than-micro microcontroller breadboard, using a Zilog Z80-compatible processor to run code loaded into external static RAM (SRAM).

"This is a collection of projects found on the web, assembled my way," Figueiredo explains of the work, which is effectively four projects in one: an Arduino Mega-compatible microcontroller board that writes to SRAM; a breadboard computer built using a Zilog Z80 eight-bit microprocessor; a 555 timer-based clock; and Figueiredo's own creation, a Cobbler to interface the Arduino to the rest of the system.

The question to be asked, of course, is if you have an Arduino already, why would you need to build a separate microcontroller board using a processor design launched in 1976 — though, to its lasting credit, still in production today. The answer is, entirely reasonably, for fun — and what Figueiredo has built does indeed look fun, providing you're not the one who has to run all the jumper cables.

The heart of the system is an implementation of the Bread80, a Z80-based microcomputer built on a breadboard — itself based on a series of video published by Ben Eater on the topic. While originally planning to use the Z80 to clock the system, Figueiredo found that unreliable in his build — so turned to Eater's design to switch to a 555 timer based clock. A sketch running on an Arduino Mega, written by John Long, allows data to be written to the SRAM where it's accessible to the Z80.

The physical interface between the Arduino Mega and the SRAM is Figueiredo's "Cobbler", with a Python-based parser to ease loading programs into the SRAM via the Arduino IDE. At present, the project is complete enough to run programs — but Figueiredo has plans to extend it still further with the introduction of external sensor components.

More details are available on Figueiredo's Hackaday.io project page, including links to the source code on GitHub under an unspecified open-source license.