Programming instructions

Reference
Project Lead The Way © and Carnegie Mellon Robotics Academy © / For use with VEX
®
Robotics Systems
Timers • 1
Timers are very useful for performing a more complex behavior for a certain period of time. Wait
states (from wait1Msec) don’t let the robot execute commands during the waiting period, which
is ne for simple behaviors like moving forward. If calculations or other actions need to occur
during the timed period, as with the line tracking behavior below, a Timer must be used.
Timers
task main()
{
bMotorReected[port2]=1;
ClearTimer(T1);
while(time1[T1] < 3000)
{
if(SensorValue(lineFollower) < 45)
{
motor[port3]=63;
motor[port2]=0;
}
else
{
motor[port3] = 0;
motor[port2] = 63;
}
}
}
First, you must reset and start a timer by using the ClearTimer() command.
Here’s how the command is set up:
ClearTimer(Timer_number);
The VEX has 4 built in timers: T1, T2, T3, and T4.
So if you wanted to reset and start Timer T1, you would type:
ClearTimer(T1);
Then, you can retrieve the value of the timer by using time1[T1], time10[T1], or time100[T1]
depending on whether you want the output to be in 1, 10, or 100 millisecond values.
In the example above, you should see in the condition that we used time1[T1]. The robot will track
a line until the value of the timer is less than 3 seconds. The program ends after 3 seconds.
Timer in the (condition)
This loop will run “while the
timer’s value is less than 3
seconds”, i.e. less than 3
seconds have passed since
the reset. The line tracking
behavior inside the {body}
will continue for 3 seconds.
Clear the Timer
Clearing the timer resets
and starts the timer. You
can choose to reset any
of the timers, from T1
to T4.
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