Lesson 1: Leaf Cycle

At the beginning of spring, leaves start as tiny buds and grow through the summer, where they reach their full size. When summer ends, the autumn leaf cycle begins! This is when spring and summer rainfall decreases, and trees in mountain areas get less water from snow runoff. The days are getting shorter, which means less sunlight and colder temperatures. This is a problem for trees since their food source is sunlight and water (you might know this process as photosynthesis). So trees cut off nutrients like chlorophyll to the leaves by forming a layer of special cork cells at the base of each leaf. This keeps the tree’s trunk, branches, and roots alive during the winter while living off stored food until spring. Chlorophyll is what makes plants green, so as it disappears, tree leaves’ true colors, like yellow and orange, start to come out. 

As chlorophyll production stops, anthocyanin production starts. Anthocyanin is a pigment that appears red in trees but can also be red, purple, blue, and black elsewhere in nature. Some trees have more anthocyanin than others, so the yellow and orange stage is skipped and the leaves turn red right away. However, this process isn’t always uniform. One tree, and one leaf, can have multiple colors! 

Brown leaves are a result of two things: sunlight and cold. If the fall season is very sunny, the sunlight will break down the pigments in the leaves, resulting in brown leaves. This doesn’t necessarily mean the leaves are dead! The only thing that can really kill a leaf is the cold. 

At the end of the autumn leaf cycle, the leaves fall to the ground and decomposers turn the leaves into food for the soil.

Before diving into coding the leaf cycle, make sure you have done the setup lessons in the “Getting Started” module. These lessons include:

• Learn how to use the remote control
• Setup and Pair to Blockly
• Learn how to use Blockly
• Know how to trim your drone

Now you are all set! Move on to the next step for an introduction to basic flight commands.

Open Blockly for CoDrone Mini. Pair your drone and then copy this code.

When you’re ready, press the green triangle. What happens?

Your drone should have taken off, hovered for 2 seconds, then landed.

Try changing the number, also called a parameter, inside of the hover block, which is a function. All the blocks on the screen are functions, but not all functions have parameters. What happens when you change the number? Or if you takeoff and land two times in a row?

There are four basic flight movements: roll, pitch, yaw, and throttle. Each direction can be positive, zero, or negative.

For example, here is how you would take off and move forward (positive pitch) for 2 seconds. These blocks are found in the Senior blocks under “Flight Variables”.

Notice:

•  To go forward use the set_pitch, put a positive number from 1-100.
• The set block must be accompanied by the move block. The duration of the movement in seconds is the parameter.
• Finally, don’t forget to land!

You can also fly backward.

You can also combine movements! Here is how you fly in a diagonal to the back and to the right.

Be careful when you use multiple directions in a flight program. If you set a value, the drone will keep that value for the whole program unless you change it back to zero! For example, use the set pitch block to reset the value back to zero if you want the drone to stop flying forward with the next movement.

Experiment with all four flight movements, positive and negative. When you’re ready for your challenge, see the next step.

You will be coding your drone to “fall” like a leaf. Your drone will rise up in the air, then sway side to side while falling down and changing the LED color.

It helps to write pseudocode before going to write your program. Pseudocode is when you write your code in “plain language”, or in a way that someone who may not be a programmer can understand. It is almost like a plan for what your code should look like in the end.

• Takeoff and throttle up as high as they can without getting too close to the ceiling. 
• Turn the LED green and “fall” while rolling to the right
• Turn the LED yellow and “fall” while rolling to the left
• Turn the LED orange and “fall” while rolling to the right
• Turn the LED red and “fall” while rolling to the left
• Land 

To “fall”, you can set the throttle to -15 while switching your roll parameter from right to left.

First, you will need to learn about the drone’s LED, which stands for “light-emitting diode”. Your CoDrone Mini has 1 RGB LED on the main body. RGB stands for red, green, and blue. Using the three colors, you can create almost every color imaginable!

The most basic LED block is found in the Junior blocks. This block allows you to change the color of the LED built into the drone. Open the lights category and find the set LED color block. Pick a color and brightness then run your code.

If you want to pick the colors using RGB values, you can use the Senior block and input the 3 values from 0 to 255. After doing a little bit of Googling, you know that you can make the four colors of the leaf cycle using this code and RGB values. We have added a “Sleep” block under “Senior Timing” to help you see the colors better.

Now get to coding! Your code should look something like this. You can change the values of the parameters depending on how much room you have for your drone to fly in.

If you’re really feeling up to the challenge, change the basic LED blocks to the Senior ones and use RGB! Or get creative and come up with some other colors.

Now that you have a general understanding of flight movements, it’s time for a challenge.

Pick a letter in the word “fall” and code your drone to fly in the shape of that letter. Make multiple programs for each letter for an extra challenge and run them in order to spell out the whole word.

The letter “L” might look like this: