Well Mowerfreak,
It's a lot simpler than a car ECU, as it operates from a single input, which both powers the module and controls the spark timing. Car ECU's operate from numerous sensor inputs; manifold air pressure, crank angle, engine temperature, engine rpm, Exhaust Gas Oxygen, to name a few.

The first really successful small engine solid-state ignition module was actually an Aussie invention, back in the mid 1970's.
It was first marketed by Atom Industries [still in business today] as a retrofit part, in several versions.
http://www.atomindustries.com/about-us/

You can find some circuit diagrams in the US Patent for it, https://www.google.com/patents/US4163437

And a potted history: http://www.powerhousemuseum.com/aus...amp;Section_id=1020&article_id=10024

Once the patents expired, it became open slather for makers of clone units, so Atom ceased manufacture.

There are still just a few NOS units available ex the USA, though; e.g. http://pickersyard.weebly.com/atom-universal-electronic-ignition-module.html

Cheers,
Gadge

"ODK Mods can explain it to you, but they can't understand it for you..."

"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."