The robot arm being used in our project is the ST Robotics R12. The purpose of the arm is to position an ultrasonic sensor against pipes to measure their thickness, thus checking for deterioration. The only software interface provided with the arm was a proprietary Windows client, which allows one to connect to the arm, send commands, and read the responses. However, this software did not cover our needs. The first problem was that we wanted to use ROS for the project, but ROS only runs on Linux. Second, the Windows interface did not provide an easy way to programmatically control the arm. As such, we needed to create our own solution.

Luckily, the Windows client does not do any command processing. The arm is controlled using Roboforth commands, which is a proprietary language developed by ST based on Forth. The Roboforth commands are sent as-is and processed by a microcontroller on the arm itself. The microcontroller sends the resulting signals to a separate digital signal processor which in turn drives the motors. Not having to do any command processing on the client-side, made our job quite easy. I was able to write a simple Python script to open a serial connection with the arm and provide an API to read and write to it. I also created a command-line shell program to control the arm interactively, and bundled it all into a Python package.

The Python package is now being used as a back-end for the ROS node we are developing for the arm. The code for the package is open-source, so I hope that others working with the R12 find it instructive and useful.