Hi Malcolm,
It's already very complicated to make small changes to an old INDI driver, to create a new one is much more complicated. At least when not a software developer which I'm not.
I'm working an a new focuser, I will use the open source project MyFocuserPro2 and control it from an Arduino device. Yesterday I setup the Arduino system and got it to run okay. Now I just have to change the code to let it do how I want the focuser to work.
I have it documented here how it proceed:
http://www.astrofriend.eu/astronomy/...us-driver.html
Lars