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THE AUTHORS OF THIS SOFTWARE ACCEPT ABSOLUTELY NO LIABILITY FOR ANY HARM OR LOSS RESULTING FROM ITS USE. IT IS EXTREMELY UNWISE TO RELY ON SOFTWARE ALONE FOR SAFETY. Any machinery capable of harming persons must have provisions for completely removing power from all motors, etc, before persons enter any danger area. All machinery must be designed to comply with local and national safety codes, and the authors of this software can not, and do not, take any responsibility for such compliance.

This software is released under the GPLv3.


There is work in progress on documentation:

IRC: #stmbl on

STMBL is an open source servo drive designed for Retrofitting CNC machines and Robots. It supports Industrial AC and DC servos with up to 320V and 2kW (see specs for details).

Documentation about the PCB and pinout of the feedback connector:

Hardware version 4.1

top bot case1 case2

Driving a Bosch Turboscara

Driving a Manutec Robot

Driving a Weeke BP12 VMC

Driving a Haas VF0 (Spindle + Axes)


Supported Motors

  • Synchronous AC Servos
  • Asynchronous AC Servos
  • DC Servos
  • 2 Phase HF spindle motors

Supported Feedback systems

  • Resolvers
  • Incremental encoders
  • sin/cos encoder interpolation
  • Mitsubishi absolute encoders
  • Sanyo Denki absolute encoders
  • Yaskawa absolute encoders
  • Tamagawa SmartAbs
  • EnDat
  • BiSS
  • SSI
  • Sanyo Denki wire-saving incremental encoder

Supported Position/Velocity Commands Inputs:

  • Smartserial
  • Quadrature
  • Step/direction
  • RS485


  • Sensorless FOC


  • hw/spice/ Spice simulation for resolver interface
  • hw/kicad/v4.0/ kicad files for version 4
  • src/ STM32F4 code, command, feedback and control loop
  • stm32f303/ STM32F3 code, running on the HV side, generating PWM
Commercial Applications

Should you find the GPL license insufficient for your needs, other licenses can be purchased from my company.

Likewise, please contact us should you wish to fund the further development of this project, or are interesed in custom hardware, software, or commercial support.