Getting Started

Why PROS?

VEX robots run on a V5 Brain—a 32-bit ARM processor running at 400 MHz. You can program it with VEXcode (a beginner-friendly IDE), but for competition-level code teams use PROS (Purdue Robotics Operating System).

PROS gives you:

• A full real-time operating system with true multitasking (FreeRTOS under the hood)
• A standard C++ toolchain (GCC), so you can use templates, lambdas, STL containers, etc.
• A rich API mirroring the official VEX SDK
• A package manager (pros conductor) for community libraries like LemLib

Why LemLib?

LemLib is an open-source motion-control library built on top of PROS. It provides:

• Odometry – tracks your robot's X, Y, and heading on the field
• PID movement – moveToPoint, turnToHeading, swingToHeading
• Path following – smooth curves via Bézier paths
• Chassis abstraction – configure once, call motion functions everywhere

In this codebase, the Chassis class extends lemlib::Chassis to add custom distance-reset methods (covered in depth later).

Installation

1. Install PROS CLI.
   Download the installer for your OS from pros.cs.purdue.edu or install via pip:

   pip install pros-cli

2. Install the VS Code extension.
   Search for "PROS" in the VS Code Extensions marketplace and install it. It wraps the CLI and gives you one-click upload.
3. Create a new project.

   pros conduct new-project my-robot --target v5 --version latest

   This scaffolds:

   my-robot/
   ├── include/
   │   ├── main.h       ← PROS entry-point header
   │   └── api.h        ← full PROS API
   ├── src/
   │   └── main.cpp     ← initialize, autonomous, opcontrol stubs
   ├── Makefile
   └── project.pros

4. Add the LemLib template.

   cd my-robot
   pros conduct add-depot https://lemlib.github.io/LemLib/depot.json
   pros conduct apply LemLib

   This downloads LemLib headers into include/lemlib/ and the library binary into firmware/.
5. Build and upload.

   pros make          # compile
   pros upload        # send to Brain over USB

   Or use the PROS VS Code extension's toolbar buttons.

Project Entry Points

PROS defines four callback functions that you fill in:

Here is the minimal initialize() from this robot:

src/main.cppvoid initialize() {
  pros::lcd::initialize();   // Start brain LCD display
  chassis.calibrate();        // Zero IMU + tracking wheels
  pros::delay(100);

  // GPS sensor physical offset from robot center (converted m → inches)
  gps.set_offset(.75/39.37008, 4.5/39.37008);
  chassis.setPose(0, 0, 0);  // Starting position is the origin

  optical.set_integration_time(20); // Fast color sampling (ms)
  optical.set_led_pwm(100);

  // Background task: print robot state to LCD every 50 ms
  pros::Task screen_task([&]() {
    while (true) {
      pros::lcd::print(2, selectedAuton.c_str());
      pros::lcd::print(5, "X: %f", chassis.getPose().x);
      pros::lcd::print(6, "Y: %f", chassis.getPose().y);
      pros::lcd::print(7, "Theta: %f", chassis.getPose().theta);
      pros::delay(50);
    }
  });

  pros::lcd::register_btn1_cb(on_center_button); // Auton selector button
}