Köbi: Robotic Puppeteering

Setup

Köbi is a 6-channel wireless stepper controller consisting of a SparkFun ESP32 Thing (red) and a breakout shield (white). The latter is inspired by RAMPS and accomodates six stepper motor drivers (TMC2130 StepSticks, green), optical endstop sensors and fan control.

The software on the ESP32 provides an OSC (Open Sound Control) server. This, in combination with a matching tablet GUI for the modular TouchOSC app allows easy control of the steppers (which are the six thread spools).

Alternatively, the module can be controlled by any other OSC client. The OSC endpoints are documented at the end of this page.

No strings attached!
Spindles with threads

Features

500g per thread
Velocities up to 2m/s
Wireless control
Sub-centimeter precision
(Almost) unlimited thread lengths
Position and speed feedback for every channel
Self-calibration using optical markers on the threads (TODO)
Motor drivers configured using SPI, allowing for:
- Microstepping reconfiguration (during operation)
- Current control
- Load estimation (TODO)
- Count of missed steps if overload occurs (TODO)
Easily extendable code written in Micropython
Wireless console (WEBREPL) and code update (FTP)
Additional I2C / SPI / GPIOs broken out

There are a ton of things you can hook it to. Feel free to reuse!

Software + Firmware

The ESP32-Board runs a special build of the Micropython firmware due to two requirements:

The PWM hardware module, which generates the pulses for the stepper motors, is currently not supported by Micropython. This special build includes a Python module supporting it, implemented in C: The MCPWM module.
The Python module for the Trinamic TMC steppper drivers (which holds names and descriptions to dozens of its registers) had to be frozen in order to save memory: The TMC module. (TODO: Not published yet)

How much do you need? To get you started with the software, each of this three guides covers a different level:

Getting started: Setup and interact with Köbi using a tablet and the default OSC API
Hacking: Extend Köbis functionality by modifying the Micropython code running the ESP32
Developing: Modify the Micropython firmware (written in C) to improve on the modules MCPWM or TMC. These are part of the modified Micropython built, ie. “frozen”