1C: Variables

Make sure that your CoDrone Mini is paired before starting the lesson! If you forgot how to do this, make sure to review how to pair to Blockly here.

Variables are a way to store information in a program, and they’re used most often to store values. If you’re playing a game on your phone or elsewhere, there’s a variable to store your score, another one for your lives, and maybe another one for your time. With your CoDrone Mini, you might use them to store the value of a sensor, the speed of your drone, or how long it will travel for.

Variables are great if you have a lot of values in your program! For example, you might have a long, complex program with multiple places where you need to change the speed. Without a variable, you would need to change all of the numbers, which leaves a lot of room for error. With a variable, you only need to change the variable’s value at the top of the program.

To create a variable, go to the pink variables menu in Blockly and click on the gray create variable… block.

You’ll be asked to name your variable, and this can be whatever you like! Just make sure it’s something that you’ll remember and makes sense with what you’re doing. 

Once you’re finished creating your variable, the variables menu will have new blocks for you to try out!

One of the blocks you’ll see in the variables menu is set _ to, which will set your variable to whatever value you choose. To use it, drag it to the top of your code and then go to the gray math menu. From there, you can just use a number block, or you can use more complex blocks that will make your math teacher super proud of you!

Preview for the next step: you can also set your variables to get the value of other variables!

When you need to recall, or use the information from, your variable, you can use the get block from the variables menu. In Blockly, you’ll usually end up putting this in any block that has a space for a value. However, like we said in the last step, you can also set a variable to get the value of another variable! This is useful if you program events that are dependent on each other.

If you need to change your variable, you have a couple of options. 

• To change it throughout the program, you can just type in a new value in the math block next to the set variable block. 
• If you want to change it in a certain part of your program, you can use the change by block in the variables menu. Drag the block to where you need it in your program and type in how much you would like to change the variable’s value by. NOTE: changing in this place will keep the variable at that value for the rest of the program until you change it again.

Try out the program in the image! What happens to the length of each side as the variable’s value changes?

Challenge: Shuttle runs

If you’ve ever been in gym class or on a sports team you’ve probably done a shuttle run: you start at one side, run to a marker, and then run back. Then you run to a marker that’s a little farther away and run back. This keeps going until you’ve reached the other side of the gym or the field and you’re out of breath.

You’re going to have your CoDrone Mini do the same thing! Set a variable to 1 after takeoff. Program your drone to fly forward for the value in the variable and then fly back for the amount in the variable. Next, increase the value in the variable and repeat. Your drone should do 4 shuttle runs, so make sure you have enough room to fly!