Session 11 Intro to FRC API

What is an API? API stands for application programming interface It’s a set of routines, protocols, and tools for building software You can think of it as a bunch of classes that does stuff for us If we didn’t have an API, programming a robot in 6 weeks would be impossible for most people

New Robot Project Go to File > New > Other… Open the “WPILib Robot Java Development” folder Select “Robot Java Project” and click next If you don’t have that folder: https://wpilib.screenstepslive.com/s/4 485/m/13809/l/145002-installing- eclipse-c-java

3 Main Types of Robot Projects Command-Based Robot A more complicated project for more complicated robots Iterative Robot Much more simple, but functionality is more limited Sample Robot Just the raw basics. Used for testing small things, or for highly advanced control flow.

New Robot Project Give your project a name Leave the package as is That’s how packages are supposed to be named Select “Iterative Robot” Click “Finish”

Looking at your new project Robot.java – the main class Referenced Libraries – the API wpilib – main robot stuff networktables – network communication stuff JRE System Library – what java version the project runs on

Robot.java IterativeRobot – the parent class robotInit() – called when the robot starts up periodic methods – called periodically while the robot is running All of these methods were inherited from IterativeRobot

FRC Driver Station The software that controls the robot from your computer First tab is the operation tab (left half of the screen)

Robot Run Modes TeleOperated – a human controls the robot Autonomous – the robot does stuff itself Practice – a simulation of a real match Test – anything you want it to be

Misc Information Elapsed Time – how long the robot has been running PC stats Window – how the DS appears windowed / fullscreen Team Station – where you are Can get this from the API

Robot Information Team # - ours is 5002 Battery Voltage – battery life Communications – if the DS can “see” the roboRIO Robot Code – if the roboRIO has code on it Joysticks – if a joystick is plugged in

Logs The log shows errors that happen while the robot’s running The chart shows packet loss % and other information about the roboRIO Third tab is both of them at once

Driver Station: Diagnostics Tab Shows what the DS can communicate with FMS – Field Management System, the thing at a competition Lets you reboot roboRIO Also shows version and memory usage

Driver Station: Setup Tab Team Number – determines what IP the DS looks for Practice Timing – the timing of practice mode Don’t touch dashboard type and protocols for now

Driver Station – USB Devices Tab Shows any joysticks plugged in Says what buttons are pressed Gives values of the axes

Driver Station – Power & CAN Tab Faults – very bad errors CAN Metrics – we’ll get into later

Motor Controllers They control motors via a signal from the roboRIO Simple ones use a PWM signal Advanced ones use CAN

Robot Wiring PWM ports on the right control basic motor controllers Use the number on the port to determine which one you’re controlling in code

Classes for a Basic Program Joystick – gets axes and buttons from a joystick Constructor takes which port the joystick is plugged into Talon – controls a standard Talon SR motor controller Constructor takes the PWM port it’s plugged into RobotDrive – a utility class that drives a robot Constructor takes the motor controllers

Writing the Code: Declaring Variables Declare your variables If you get an error, then the classes haven’t been imported Hover over it with your mouse and select the “Import” option

Writing the Code: Initializing Variables Make a constructor and initialize your variables in it First joystick will be 0 Need to look at roboRIO for the PWM ports of the Talons RobotDrive takes those motor controller objects

Writing the Code: TeleOp Driving around the robot in teleop is as easy as this line of code: arcadeDrive takes a joystick object and uses it to control the robot The true is for squared inputs Makes lower values of the axes less sensitive Allows for more precise control over the robot

Writing the Code: Autonomous Set a motor controller’s speed manually by using the method public void set(double speed) 0 is neutral, -1 is full reverse, 1 is full forward

Uploading the Code Connect to the roboRIO (USB, ethernet, or wireless) Run the project as “WPILib Java Deploy” Wait for the roboRIO to load the new code Run the robot