I added circuitry for comtrolling the motor of the automatic dropper. I don't think I can add a lot more to this board now - I'm starting to think about a proper PCB for mark IV (I may experiment with one of the services that etches them for you rather than trying to do it myself though...)

Getting the motor to work was more of a challenge than it should have been due to me not understanding the difference between the VCC and VCC_EXT connections on the butterfly. I connected the motor on the same pin as the onboard piezo, and this meant I had to use a 0 to turn the motor on rather than a 1 (the piezo crackles if held low).

Using the pizeo pin had a coupe of advantages. Firstly it means I can easily test the motor drive/speed code without a motor attached, and secondly it means I can use one of the onchip timer circuits to control the motor speed without needing any interrupt code (which I am trying to avoid because I want my timings to be as repeatable as possible). It may be that the piezo whine while the motor is running will become annoying (in which case I may rethink).