the robot that draws on vertical surfaces
yes, it's just as amazing as it sounds and equally unnecessary...you're gonna love it.
About the gocupi
The Raspberry Pi controls two stepper motors which attach to a non-porous vertical surface using suction cups. The motors move a pen hanging from threads to draw stuff out on a whiteboard or any vertical surface. A program written in Go runs on the Pi, it sends movement commands over serial to an arduino, which then pulses the step pin on the stepper drivers to make the stepper motors move.
This project is different from most other Polargraphs in that there is no step generation code on the arduino, everything is calculated in Go and then the arduino just receives a stream of step deltas that it stores in a memory buffer and then executes. Since all logic is written in Go running on the Pi it allows using more advanced interpolation models for smooth drawing, not needing to use fixed point or single precision floats for calculations, not needing to reflash the arduino often when making code changes, etc.