LEDs

LED stands for “light-emitting diode”. A diode is an electronic device that allows an electronic current to flow in only one direction. LEDs are beginning to replace traditional light bulbs because they are more efficient.

Your CoDrone has 6 RGB LEDs: one on each of the four arms, one for the eyes, and one for the tail. RGB stands for red, green, and blue. Using the three colors, you can create almost every color imaginable! Aside from making your drone look cool, LEDs provide another form of feedback. For example, the tail light can tell you the connection status of your drone. A solid green tail light means your drone is connected, while the flashing green light indicates it’s in pairing mode. While you cannot change the colors of this particular LED, the remaining 5 LEDs can be programmed to produce any color and pattern that you want!

CoDrone provides functionality so that you can either change the arm LEDs, eye LEDs, or both at the same time! Regardless of which you choose, they will all look similar to one of the following:

• set_all_led(color, mode)
• set_all_led(color, mode, interval)
• set_all_led(red, green, blue, mode)
• set_all_led(red, green, blue, mode, interval)

This might be a little overwhelming since there are 4 ways to use a method, so let’s go over what all of these parameters mean.

Color – CoDrone has a predefined set of colors that you can choose from! Click here to see the complete list of colors.

Red, green, blue – If you want to make your own color instead of a preset color then you can use the method with these parameters. Remember that an LED produces a color as a combination of red, green, and blue (hence the name RGB LED). All of these values range from 0 to 255 corresponding to the color’s intensity, 255 being the highest. For example, the RGB values for the color red correspond to [255,0,0]. What are the RGB values for blue and green? What about purple? You can use an RGB color picker to find out!

Mode – The mode refers to the light pattern that you want to choose:

• SOLID keeps the LEDs on
• BLINK flashes LEDs on and off
• STROBE cycles through all of the colors
• DIMMING fades the LEDs in and out
• PULSE turns on and off LEDs on each arm before moving to the next arm
• REVERSE_PULSE does the same as PULSE but in the opposite direction
• OFF turns the LEDs off

Interval – The interval of the light pattern, except for in the case of SOLID. For SOLID mode, this refers to the light’s brightness. This is a positive integer and keep in mind that it represents the frequency (per second) of the pattern.

Now that you know the general structure, you may be wondering what the method names are. There are seven methods that you can use to change the LEDs. The first set of methods changes either only arm LEDs, only the eye LED, or all of them at the same time.

• set_arm_led()
• set_eye_led()
• set_all_led()

You may have also noticed that when you initially pair to your CoDrone the eye and arm LEDs are always red. You can also change these default settings using the following:

• set_arm_default_led()
• set_eye_default_led()
• set_all_default_led()

For example, let’s say you wanted to change the default arm LED to blinking purple instead of the default red:

drone.set_arm_default_led(CoDrone.Color.Purple, CoDrone.mode.BLINK, 45)

You can also use RGB values to achieve the same effect:

drone.set_arm_default_led(255, 0, 255, CoDrone.mode.BLINK, 45)

Now the next time you pair your drone the arms will flash purple. Keep in mind that using this method will not change the colors of your drone while flying, only when you reset the drone. If you want to change your CoDrone’s colors the moment you call the method in the code, use the first set of methods. For example, this code will pulse arm LEDs to blue-green at an interval of 100:

drone.set_all_led(0, 255, 255, CoDrone.mode.PULSE)

To reset the CoDrone LEDs back to their default colors, use the reset method with no parameters:

drone.reset_default_led()

Try some of these challenges to practice using the methods to change LEDs:

• Make your CoDrone unique by changing the default color. If you are in a class make sure everyone has a different color!
• Change the colors of your drone using a keyboard. For example, pressing the ‘B’ key changes your LEDs to blue but pressing the ‘P’ key changes your LEDs to purple. If you’re not quite sure how to do this, go to lesson 3B: User Input to find out.
• Use one key, such as the spacebar, to switch between two colors. Hint: Use a variable to hold the binary state of the current color to determine which color to switch to if the key is pressed.

If you want to see LEDs in your flight programs, add the LED commands where you would like to see them. This can be before or after a flight movement. Run this program in PyCharm so you can see everything in action!

import CoDrone

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

drone.set_arm_led(194, 152, 251, CoDrone.mode.BLINK, 50)
drone.takeoff()	# takeoff for 2 seconds

drone.set_arm_led(0, 206, 216, CoDrone.mode.BLINK, 50)
drone.set_pitch(30)	# Set positive pitch to 30% power
drone.move(2)	# forward for 2 seconds

drone.set_arm_led(253, 109, 47, CoDrone.mode.BLINK, 50)
drone.set_yaw(-50)	# Set negative yaw to 30% power
drone.move(2)	# turn left for 2 seconds

drone.set_arm_led(15, 153, 0, CoDrone.mode.BLINK, 50)
drone.land()	# lands the CoDrone
drone.close()	# disconnects CoDrone

• Drone Light Show: Create coordinated drone light shows with multiple CoDrones , either autonomous or manual flight.
• Infection: One or two players (depending on class size) start off as zombies (Red LEDs). The rest of the players start off as Survivors (Green LEDs). Zombies try to tag survivors. If a survivor is tagged, they need to change their drone LEDs to Red and join the zombies in infecting the rest of the survivors. Set a time limit appropriate for the level and size of the class.
• Capture the Flag: Split the class into two teams and set up a designated area for team bases on opposite sides of the playing area. Each team should have a designated CoDrone color so they know who is on their team. The goal of the game is for a team to land on the opposing team’s base, “pick up the flag” by changing their drone color, and fly back to their home base without getting knocked out of the sky. If they do, they need to change their drone LED back to the team color.

Challenge: Spy Mission

The first system of electrical telecommunication was the telegraph. It was a device that sent pulses of electricity, either long or short, to send messages. Letters were defined by unique combinations of long and short beeps, called Morse Code. You may be able to recognize this message:

. . . _ _ _ . . . 

This message reads SOS!

Look up the Morse Code alphabet and learn some letters. Try coming up with a method to send messages using Morse Code with your CoDrone’s LEDs. If you want, pair up to decode each other’s messages.

*Hint: Create a list with a combination of 1s and 0s. Each ‘1’ corresponds to a long flash and each ‘0’ corresponds to a short flash. Within the for loop, have a conditional that checks if the value is a 1 or a 0. Change colors and sleep values accordingly.