CAN Protocol

Commonplace Robotics uses the CAN field bus to send position set point values from the robot controller to the joint modules. The applied protocols are custom, but quite simple.

Two version are used:

• CPRCAN: 16 bit position data used for Mover4 and Mover6 robots and Slider platforms
• CPRCANV2: 32 bit position data used for SRA and Mover6-2016 (understands both, CPRCAN and CPRCANV2) robots.

The position set point messages have to be send in a loop with e.g. 20 Hz. The application has to verify that this loop has a constant cycle time. If the jitter is too big the motion control modules might get into a communication loss error state. Additionally the application has to send state change messages like reset-all-errors and enable-motors.

The joint modules answer with an error code that provides the current state.

Resources:

• Documentation: CAN protocol documentation
• Linux examples: C sources can be downloaded at www.github.com/CPR-Robots
• C# demo: Source code for Visual Studio Express 2012

Currently we are updating the example source code to the cprcanv2 protocol. Please get in contact if you need these sources.