RobotPy

• Small computer used to control a robot
• Lots of input and output connections
• No display … write on laptop and download
• Typically runs code written in Java or C++

Both Java and C++ are:

• compiled
• difficult to learn
• quite verbose

Here is a function written in Java:

public int[] increment(int[] array) {
    int[] newarray = new int[array.length];
    for (int i = 0; i < array.length; i++) {
        newarray[i] = array[i] + 1;
    }
    return newarray;
}

Here is the same function in Python:

def increment(array):
  return [i + 1 for i in array]

Allows students to write robot code for RoboRIO in Python

Note: We need to use Python version 3.4 or larger

robotpy-wpilib: the python implementation of WPILib for FRC pyfrc: provides unit testing, realtime robot simulation, and easy upload capabilities for your RobotPy code roborio-packages: Various python packages for the RoboRIO platform installable by opkg, including the python interpreter and numpy robotpy-wpilib-utilities: Community focused extensions for WPILib pynetworktables: python bindings for NetworkTables that you can use to communcate with SmartDashboard and/or your robot. pynetconsole: A simple netconsole implementation in python robotpy-cscore: Python bindings for cscore, a powerful camera/streaming library roborio-vm: Scripts to create a QEMU virtual machine from the RoboRIO image file

• Install the pyfrc project on your laptop (using pip)

  pip3 install pyfrc
  

• Install supporting Python modules on your laptop
• Install RobotPy on the RoboRIO

• Your robot code must start within a file called robot.py

• Add the following to the top of our code:

  import wpilib
  

• Inherit from a parent class:

  class MyRobot(wpilib.IterativeRobot):
  

• Create a robotInit function to create instances of your motors and hardware devices, e.g.

  def robotInit(self):
      self.motor = wpilib.Jaguar(1)
  

• Most WPILib examples are written in Java
• The WPILib implementation in RobotPy is very similar
• Examples just need to be translated

Want to create an object to interact with the Jaguar motor controller through a PWM? Use bpython:

pip3 install bpython

Use it instead of python, and hit Tab to learn:

(robotpy) root@blobfish:~# bpython
bpython version 0.16 on top of Python 3.5.2 /root/.virtualenvs/robotpy/bin/python3
>>> import wpilib
>>> wpilib.Jaguar(
┌─────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ wpilib.Jaguar: (self, channel)                                                                      │
│ A Jaguar Constructor.                                                                               │
│                                                                                                     │
│ :param channel: The PWM channel that the Jaguar is attached to. 0-9 are on-board, 10-19 are on the  │
│ MXP port                                                                                            │
└─────────────────────────────────────────────────────────────────────────────────────────────────────┘

Let’s create a virtual environment:

pip3 install virtualenvwrapper
source /usr/local/bin/virtualenvwrapper.sh
mkvirtualenv robotpy

To use it, run the following (or put in .bashrc):

source /usr/local/bin/virtualenvwrapper.sh
workon robotpy

PWM

Pulse-width modulation for variable speed fans