Robot Simulator

An important (but often neglected) part of developing your robot code is to test it! Because we feel strongly about testing and simulation, the RobotPy project provides tools to make those types of things easier through the pyfrc project.

The pyfrc robot simulator allows very simplistic simulation of your code in real time and displays the results in a (ugly) user interface. To run the simulator, run your with the following arguments:

Windows:   py -3 sim

Linux/OSX: python3 sim

As there is interest, we will add more features to the simulator. Please feel free to improve it and submit pull requests!

A new feature as of version 2014.7.0 is the addition of showing the robot’s simulated motion on a miniature field in the UI. This feature is really useful for early testing of autonomous movements.


For this to work, you must implement a physics module (it’s a lot easier than it sounds!). Helper functions are provided to calculate robot position for common drivetrain types (see below for details). There are physics examples provided in the RobotPy Examples Repository for each supported drivetrain type.

Communicating with SmartDashboard

The simulator can be used to communicate with the SmartDashboard or other NetworkTables clients. For this to work, you need to tell SmartDashboard to connect to the IP address that your simulator is listening on (typically this is Using the original SmartDashboard, you need to launch the jar using the following command:

$ java -jar SmartDashboard.jar ip

If you are using the SFX dashboard, there is a configuration option that you can tweak to get it to connect to a different IP. You can also launch it from the command line using the following command:

$ java -jar sfx.jar

Real Joystick support via pygame

If you have pygame installed for Python 3, when you run the simulator any supported joysticks you have plugged in should automatically provide joystick input to the simulator.


Installing pygame requires having a compiler installed, as it has many binary dependencies. It can be a tricky thing to accomplish, please refer to the pygame documentation for the right way to install it for your platform.

New in version 2015.3.6.

Gazebo simulation

This is currently experimental, and hasn’t been updated in awhile. If you want to play with it now (and help us fix the bugs!), check out the robotpy-frcsim github repository.

Next Steps

The next section discusses a very important part of writing robot code – Unit testing robot code.