Bare Metal Gives This Pi Some Classic Synths

We’re used to seeing the Raspberry Pi crop up in a wide range of the projects we show you here, but it’s fair to say that they usually feature some sort of operating system. There’s another way to use a Pi, more akin to using a microcontroller such as the Arduino: by programming it directly, so-called bare-metal programming. MiniDexed is an example, and it copies a classic Yamaha professional synthesiser of the 1980s, by emulating the equivalent of eight of the company’s famous DX7 synthesisers in one unit. It takes almost any Pi, and with the addition of an audio board, a rotary encoder, and an LCD display, makes a ready-to-go unit. Below the break is a video of it in operation.

It’s fair to say that we’re not experts in Raspberry Pi bare metal programming, but it’s worth a diversion into the world of 1980s synthesisers to explore the DX7. This instrument was a staple of popular music throughout the 1980s and was a major commercial success for Yamaha as an affordable FM synthesiser. This was a process patented at Stanford University in the 1970s and subsequently licensed by the company, unlike other synths of the day it generated sound entirely digitally. It’s difficult to overestimate the influence of the DX7 as its sound can be heard everywhere, and it’s not impossible that you own a Yamaha FM synth even today if you have in your possession a sound card.

Curious about the DX7? Master chip-reverse-engineer [Ken Shirriff] exposed its secrets late last year.

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Ken Shirriff Breaks Open The Yamaha DX7

For better or worse, this synthesizer was king in the 1980s music scene. Sure, there had been synthesizers before, but none acheived the sudden popularity of Yamaha’s DX7. “Take on Me?” “Highway to the Dangerzone”?  That harmonica solo in “What’s Love Got to Do With It?”  All DX7. This synth was everywhere in pop music at the time, and now we can all get some insight from taking a look at this de-capped chip from [Ken Shirriff].

To be clear, by “look” that’s exactly what we mean in this case, as [Ken] is reverse-engineering the YM21280 — the waveform generator of the DX7 — from photos. He took around 100 photos of the de-capped chip with a microscope, composited them, and then analyzed them painstakingly. The detail in his report is remarkable as he is able to show individual logic gates thanks to his powerful microscope. From there he can show exactly how the chip works down to each individual adder and array of memory.

[Ken]’s hope is that this work improves the understanding of the Yamaha DX7 chips enough to build more accurate emulators. Yamaha stopped producing the synthesizer in 1989 but its ubiquity makes it a popular, if niche, platform for music even today. Of course you don’t need a synthesizer to make excellent music. The next pop culture trend, grunge, essentially was a rebellion to the 80s explosion of synths and neon colors and we’ve seen some unique ways of exploring this era of music as well.

Thanks to [Folkert] for the tip!