In my experience SMC ("state machine compiler", tres original no?) is better-suited than ragel for working with state machines that're easily specified as "state charts".

The difference is that ragel is oriented around consuming a stream-of-chars: the generated state machine expects to be consuming chars as input.

You can pick up on this in the writeup even though Zed's not pointing it out: he first has to define his messages as chars (eg: 'done' == 'D'), then he specifies his states + transitions in terms of those definitions.

SMC instead generates methods for each 'message' and it's the enveloping program's responsibility to call the correct method to update the state.

This is cleaner for simpler state machines.

None of this is intended as a knock on ragel, btw: it's a very solid piece of software, and for more-complicated state machines should be the go-to choice.