Timers

You’ll be using the time.process_time() function to keep track of time in your programs. The best way to explain what it does is to see it in action in PyCharm.

import time
while True:
    print(time.process_time())

Keep in mind that this is an infinite loop (see the “while True”?) so you will need to terminate your program.

What do you notice? The numbers should be increasing at a familiar rate. The value of time.process_time()returns the number of seconds that have passed since running your programming.

One way you can use timers: perform a sequence of flight events!

To keep track of how much time has passed you will need two variables: one to hold the initial time and one to hold the final time. The difference of these two values will give you how much time has passed. First, import the necessary libraries (CoDrone and time) in your program and establish a connection with your CoDrone.

import CoDrone
import time

Next, pair to your drone.

import CoDrone
import time

drone = CoDrone.CoDrone()
drone.pair()

Before your drone takes off, it needs a variable to start the time! Use begintime = time.process_time(). In this program, you’re just going to measure how long takeoff takes, so add endtime = time.process_time()after takeoff.

To subtract begin_time from end_time, you will need to include actual_time = end_time - begin_time, along with a print command for actual_time.

Finally, end your program by landing and disconnecting your drone. This is what your code should look like:

import time
import CoDrone

drone = CoDrone.CoDrone()
drone.pair()

begin_time = time.process_time()

drone.takeoff()

end_time = time.process_time()

actual_time = end_time - begin_time
print(actual_time)

drone.land()
drone.disconnect()

Let’s reuse the square code from lesson 2B: Flight Movements, but this time, you’ll put that code in a function and add timers to see how long the square code lasts. You’ll need to declare three variables: begin_time, end_time, and total_time. The variables begin_timeand end_timewill be equal to time.process_time(). The location of these two variables is important! Since these variables belong before and aher the square code, that is where you’ll get the most accurate time. Once you get the values for begin_timeand end_time, use total_timeto find the difference between them, which is also the total runtime for the square.

import time
import CoDrone
drone = CoDrone.CoDrone()
drone.pair(drone.Nearest)

def square():
            
    drone.set_pitch(30)	#	forward set at 30% power
    drone.move(2)	#	forward for 2 seconds
    drone.set_pitch(0) 
            
    drone.set_roll(-30)	#	left set at 30% power
    drone.move(2)	#	left for 2 seconds
    drone.set_roll(0)    
    drone.set_pitch(-30)#	backward set at 30% power
    drone.move(2)	#	backward for 2 seconds
    drone.set_pitch(0)
            
    drone.set_roll(30)	#	right set at 30% power 
    drone.move(2)	# right for 2 seconds
    drone.set_roll(0)

drone.takeoff()
begin_time = time.process_time()
square()
end_time = time.process_time()
drone.land()

total_time = end_time - begin_time
print(total_time, "seconds")

drone.close()	# disconnects CoDrone

You can also use timers to activate actions with if statements. However, if there are multiple if, elif, and else statements, then you’ll need a while loop to continually check for updated conditions.

import time
import CoDrone

drone = CoDrone.CoDrone()
drone.pair(drone.Nearest)

drone.takeoff()
drone.hover(2)

while True:
    # declare a variable to get time
    current_time = time.process_time()

    #print variable
    print(current_time)
 
    if current_time < 10:
        drone.set_yaw(20)
        drone.move(3)
        print("yaw")
    elif current_time < 20:
        drone.set_roll(10)
        drone.move(3)
        print("roll")
    elif current_time < 30:
        drone.land()
        drone.disconnect()
    else:
        # escape while loop
        break

Make a code that will do an action based on how much time has passed. Have your CoDrone take off and then do an action, like pitch, for 2 seconds. Then see how much time has passed and print that time. Next, create an if statement that checks if the time is less than a certain amount of time. If the condition is satisfied, do another action or two. Finally, land and disconnect.

Below is an example:

import time
import CoDrone
from CoDrone import Color, Mode

drone = CoDrone.CoDrone()
drone.pair(drone.Nearest)
drone.takeoff() 

drone.set_pitch(10)
drone.move(2)

clock = time.process_time()
print(clock)
if time.process_time() < 20:
    drone.set_arm_led(Color.Yellow, Mode.SOLID, 20)
    drone.set_throttle(25)
    drone.move(3)

drone.land()
drone.close()

Challenge: Two Minute Code

Create a code that can last for two minutes!

Rules:

• Every fifteen or twenty seconds, the CoDrone has to do a different action.
• Use a while loop that checks if time.process_time() is less than 180.
• Use if, elif, and else statements that check what time it is.
• Every 15-20 seconds, your program should do a different color, CoDrone action, or print a string.

Below is an example. It’s just missing flight commands!

import time
import CoDrone
from CoDrone import Color, Mode

drone = CoDrone.CoDrone()
drone.pair(drone.Nearest)

while time.clock() < 120:
    current_time = time.clock() 
    print(current_time)
    if current_time < 20:
        drone.set_arm_led(Color.Yellow, Mode.DIMMING, 20)
    elif current_time < 40:
        drone.set_arm_led(Color.Blue, Mode.SOLID, 20)
    elif current_time < 60:
        drone.set_arm_led(Color.Orange, Mode.REVERSE_PULSE, 20)
    elif current_time < 80:
        drone.set_arm_led(Color.Purple, Mode.DIMMING, 20)
    elif current_time < 100:
        drone.set_arm_led(Color.Red, Mode.STROBE, 20)
    elif current_time < 120:
        drone.set_arm_led(Color.Green, Mode.PULSE, 20)
        print("done")