Logically invert the pin?

We are (speaking for George here, I believe he'll agree) in agreement that the suggestion of inverting the output using @Gordon #31 suggestion af_opendrain will (and does) invert the data at the pin.

It doesn't - just follow what the docs say and try it. You get a 5v, non-inverted output from the STM32.

I'm afraid that's my last post on this thread though - I've spent way too long already.

If you want something to 'just work' then buy an official Espruino board - it's also easier for me to justify spending lots of time helping with issues :)