Line

Initializing the Line Class

A Line Tracker is created by using the following constructor:

Line(port)

This 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(brain.three_wire_port.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(units) method 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	Optional. The only valid unit for reflectivity is PERCENT.

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

# Print the reflectivity of the Line Tracker to the
# Brain's screen.
brain.screen.print(line.reflectivity())

changed()

The changed(callback, arg) method 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.
arg	Optional. A tuple of arguments to pass to the callback function.

Returns: None.

# Define a function line_changed().
def line_changed():
    # The Brain will print that the value detected by the
    # Line Tracker changed on the Brain's screen.
    brain.screen.print("Line Tracker changed")	
# Run line_changed when the value of the Line Tracker changes.
line.changed(line_changed)