Pi Zero vPiP hanging v-plotter control board

This is my Raspberry Pi Zero control board for vPiP (Whats vPiP? Its a hanging v plotter control software written in Python and Arduino firmware - it can probably be used for other drawing machines, but its main purpose in life is for use with the vPiP software - https://github.com/brianinnes/vpip).

What's a hanging v plotter? Its a drawing machine where a pen is suspended from two strings or chains attached to two motors at the top outer corners of the machine. The pen is moved by lengthenin