Tonight I've put together a little test setup on a breadboard, consisting of an Arduino Pro Micro, an ultrasonic sensor, and a button ( to act as the air pressure sensor).
First step was to get it spitting out data to the serial window; using the NewPing library I was able to get it firing out the distance measured in cm in no time.
Next step was to incorporate the MIDI code, and sure enough it started to fire MIDI data out.
Next i need to tidy up the code (using an if statement for checking the button/air pressure sensor in the future, cleaning up midi sending to only send one value and to silence the previous one).
Finally I need to write some mapping to take the slide measurements and determine what should be played.
The note that should be played on the very centre of the slide length (4th position at the 15cm mark) will be the note, bang on in the centre. Either side of that note the slide postion will determine what level of pitchbend should be applied to achieve the note for that position.