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Goal
At first sight
The schematic
The power supply
The microcontroler
The synthesiser
The ROMs
Code and memory maps
AVR cartridge
CPLD cartridge
Converting sounds
Creating the ROM
PCBs
At first sight

Speak and spell diagramDespite the relatively high cost of this toy on eBay, it did not take long to raise the money to buy me two different versions of it. The first I got was an UK version which was broken and the second one was French (whose innards are pictured left). Count between around $40 for including ground postage for a functional machine, and a few dollars for a broken one.

I was lucky, the cause of the first one's failure was a just a loose power wire and a fried zener diode. Be aware that [Grapsus] had less luck, and ended up unsoldering the chips one by one, to find in the end that the synthesizer was to blame. Betting on broken S&S isn't always worth the money if you want to get them quick and cheap.

Once received, I immediately torn the two open to confirm that their PCBs were known and findable on Datamath.org. It was the case, and I was glad not to have to deal with ugly glob-tops but beautiful through-board chips. The UK version is the oldest of the two, it is easily recognizable by its keyboard with raised keys and lack of power plug. The French version, which dates from 1979, has a membrane keyboard with a power and and headphones plugs on the side.

Inside the English version, on which I've decided to base the project, there are two PCBs welded together. A small single-sided one, and a much larger double-sided one. On the small one, there is a transformer, a bunch of transistors and a few passive components, that's the power board. Found on the large display, are a VFD (Vacuum Fluorescent display, a type of display using special voltages. LEDs weren't that common at the time), a keypad consisting of two 4x5 key matrices, and 4 integrated circuits:

  • TMC0271, which has 40 pins, the microcontroller (TMC0270, ROM version 1)
  • TMC0281, which has 28 pins, the audio synthesizer (aka TMS5100 TMC0280, ROM version 1)
  • TMC0351, TMC0352, two very special 16kB ROMs.

Speak and spell diagramBefore starting any multimeter or oscilloscope based research, I first searched arount the net to see if anyone had already spent some time on the toy, or if official documents such as patents were available and detailed enough to save me some effort.

I quickly stunbled upon the Noizeinabox project, which drives the synthesizer with an Arduino with no other purpose than to produce glitchy sounds. Later on, I came across some forum posts from Lord Nightmare who appeared to have already dealt with the subject, but I couldn't find a trace of a flash cartridge. His messages were however very useful because they directed me to the US patent #4189779 which describes the basic operation of the S&S, and gives an almost complete listing of the microcontroller's source code, which I'll talk about later.

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