mainspring VS abn6502

First off, awesome, interpreters and emulators are really fun projects. I've written a very similar project which might be useful for reference https://github.com/ncatelli/mainspring. As for parsing to your enum representation KerfuffleV2 gave a great example for nom. That being said, if you'd like to peek behind the curtain a bit for combinators and the principles behind nom, Bodil Stokke has a WONDERFUL tutorial on the topic https://bodil.lol/parser-combinators/ which will be directly applicable to what you are trying to do. Additionally, while targetted at using java, https://craftinginterpreters.com/ by Bob Nystrom is available for free online and covers the topic of writing really simple recursive decent parsers.

My code is a bit hard to read because of some APRS NRZ decoding mixed in with the KCS decoding but essentially I’m only measuring if the correct amount of cycles have passed(throwing away the other cycle data) and then detecting if the wave had a length above or below a threshold of $0600(somewhere around 1700Hz) timer1 counts (at 2MHz in my case). That leaves plenty of headroom but has pretty bad immunity to false zero crossings. You can have a look ca1irq: https://github.com/AndersBNielsen/abn6502/blob/main/abn6502rom.s

I’m using it for mine - same memory map as Ben’s. I only use the assembler for now though but will use the compiler some time in the future. It’ll probably help you get an idea how to set it up: https://github.com/AndersBNielsen/abn6502