Timer

Introduction

The VEX AIR Drone Controller’s timer keeps track of elapsed time from the start of a project. It can be used to measure durations, trigger events after a set time, or reset for new timing operations.

Below is a list of all available methods:

Action – Control the timer.

• reset – Resets the timer to zero.

Getter – Report the current timer value.

• time – Returns the elapsed time since the project started.

Callback – Trigger functions after a delay.

• event – Calls a function after a specified number of milliseconds, with optional arguments.

Constructor - Create a Timer to track time.

• Timer - Create a new timer object that can be used with these methods.

Action

reset

reset sets the timer to zero.

Usage:

timer.reset()

Parameters	Description
	This method has no parameters.

# Display the time the drone takes to climb upwards.
drone.take_off(500)
timer.reset()
drone.climb_for(UP, 500)
controller.screen.print("Time elapsed: ")
controller.screen.print(timer.time(SECONDS))
drone.land()

Getter

time

time returns the current elapsed time of the timer in the specified units — an integer for MSEC or a float for SECONDS.

Usage:

timer.time(units)

Parameters	Description
units	The time units are milliseconds MSEC (default) or SECONDS.

# Display the time in two units.
while True:
    controller.screen.clear_screen()
    controller.screen.set_cursor(1, 1)
    controller.screen.print("Time: {} ms".format(timer.time(MSEC)))
    controller.screen.next_row()
    controller.screen.print("Time: {:.2f} s".format(timer.time(SECONDS)))
    wait(50, MSEC)

Callback

event

event calls a function after a specified amount of time.

Usage:

timer.event(callback, delay, arg)

Parameters	Description
callback	A function to execute when the timer event occurs.
delay	The delay before the function is called, in milliseconds.
arg	Optional. A tuple containing arguments to pass to the callback function. See Using Events with Parameters for more information.

# Create a function to play a looping sound.
def on_timer():
    controller.sound.play(LOOPING)

# Play the sound after 4 seconds (4000 mS).
timer.event(on_timer, 4000)

Constructor

Timer

A new timer can be created using the Timer constructor. A new timer starts measuring time immediately when it is created.

Usage:
Timer()

Parameter	Description
	This constructor has no parameters.

# Display 2 timers with a 2 second difference.
wait(2, SECONDS)

stopwatch = Timer()

while True:
    controller.screen.clear_screen()

    controller.screen.set_cursor(1, 1)
    controller.screen.print("Timer: ")
    controller.screen.print(timer.time(SECONDS))

    controller.screen.set_cursor(4, 1)
    controller.screen.print("Stopwatch: ")
    controller.screen.print(stopwatch.time(SECONDS))

    wait(0.1, SECONDS)