nanoDLP

Hi guys
Apologies if this has been covered before Ive been readign for 2 hours and havent found a similar issue.

So i have a RPI3 and a ramps 1.4 board with just a single stepper driver on the Z axis with a stock 1.8 deg 1.25amp stepper motor,
Ive tested the ramps with the standard test sketch as well as stock Marlin and used pronterface to control.All works fine

SO then i connected to the RPI3
Couldnt get it to work so used SSH to check the /dev path and corrected that in my path set up . That cleared the serial connection issue.
But now im getting 'Serial communication Error short write" and have no idea what this means.

All help appreciated Thanks