Very quickly ran out of the trinkets 5k memory. Could optimise to not use floats and save 2k, but don't think it will save me.

Have switched over to an old arduino Diecimilla (ATMega168) with 16k, works well after I figured an issue with uploading/reseting at right time.

https://stackoverflow.com/questions/19765037/arduino-sketch-upload-issue-avrdude-stk500-recv-programmer-is-not-respondi/20735393#20735393?newreg=42a3dc1f81b3401ca54ca03bf5804f21

If I end up needing more I'll look at a trinket pro for a few quid more ($to £ price in UK otherwise would just get one now).