In recent times, you may have come across news of an unprecedented chip shortage. It’s not just the cutting-edge, state-of-the-art microprocessors that are in short supply; even the once-ubiquitous chips from the era when you could casually stroll into a Radio Shack are becoming increasingly rare. Interestingly, these shortages are due to a variety of factors, each with its unique set of challenges. However, in the spirit of the maker community, ingenious solutions are emerging to address these chip scarcities.
One such chip that has found itself in the spotlight is the General Instrument SP0256, a relic from the 1980s, and it’s gaining attention thanks to the efforts of one individual – Andrew Menadue. The SP0256 is a speech synthesizer chip that was ahead of its time. With the ability to store 59 distinct allophones, representing the basic sounds the human vocal tract can produce, it synthesized speech by rapidly stringing together these sounds. If you’re a fan of classic movies or iconic voices, chances are you’ve heard this chip in action. Think of “WarGames” (yes, we know it wasn’t a computerized voice) or the unmistakable tones of the late [Stephen Hawking], and you’re on the right track.
Andrew Menadue’s fascination with this vintage chip arose from his desire to breathe life into his collection of Psion Organisers, those charming relics from the 1980s that marked an early foray into pocket-sized computing. A while ago, he embarked on the ambitious project of creating a speech board for the Psion using the SP0256-AL2. However, there was a catch – these chips had become as elusive as rare gems, leaving him no choice but to craft an emulator. This emulator ingeniously utilizes an RP2040 microcontroller, neatly packaged on a PCB with the same footprint as the original SP0256 chip, allowing it to be a direct replacement. Andrew scoured the depths of the internet to unearth WAV files containing the allophones and ingeniously translated them into sequences of bytes. The result? The RP2040 now flawlessly produces the correct sounds as they are called for. Speaker issues aside, the output is impressively faithful to the original.
This isn’t the first time we’ve seen innovative uses for the SP0256; it’s made appearances in a wide range of projects, from Amstrad computers to Z80-based systems. And Andrew Menadue, with his knack for inventive solutions, is no stranger to our pages. We’ve previously featured his exploration of the voltage tolerance of the RP2040, showcasing his dedication to pushing the boundaries of what’s possible with these chips from yesteryear.