line

Initializing the line Class

A Line Tracker is created by using the following constructor:

The line constructor uses one parameter:

Parameter	Description
port	The 3-Wire Port that the Line Tracker is connected to, whether it’s a port on the Brain, or a 3-Wire Expander.

A Brain or 3-Wire Expander must be created first before they can be used to create an object with the line Class constructor.

// Create the Brain.
brain Brain;
// Construct a Line Tracker "Line" with the line class.
line Line = line(Brain.ThreeWirePort.A);

This Line object will be used in all subsequent examples throughout this API documentation when referring to line class methods.

Class Methods

reflectivity()

The reflectivity(percentUnits units) command returns the reflectivity measured by the Line Tracker. The reflectivity of the Line Tracker is an estimation based on the raw value of the sensor. A reflectivity of 0% is a raw value of 3000 or greater. A reflectivity of 100% is a raw value of 0.

Parameters	Description
units	The only valid unit for reflectivity is percent.

Returns: A double representing the reflectivity measured by the Line Tracker as a value in the range 0 - 100%.

// Get Line Tracker reflectivity in range of 0 - 100%.
double value = Line.reflectivity();

// Print the reflectivity of the Line Tracker to the
// Brain's screen.
Brain.Screen.print(value);

changed()

The changed(callback) command registers a callback function for when the value of the Line Tracker changes.

Parameters	Description
callback	The callback function to be called when the value of the Line Tracker changes.

Returns: None.

// Define the lineChanged function with a void return type,
// showing it doesn't return a value.
void lineChanged() {
  // The Brain will print that the value of the Line Tracker
  // changed on the brain screen.
  Brain.Screen.print("Line Tracker value changed");
}

int main() {
  // Initializing Robot Configuration. DO NOT REMOVE!
  vexcodeInit();

  // Run lineChanged when the value of the Line Tracker changes.
  Line.changed(lineChanged);
}