Conditionals

Code blocks used in this tutorial:

• if
• variables

Variables

In programming, we use variables to keep track of numbers and states. You can think of variables like boxes with labels.

Electronics

For this tutorial, we are going to use the expansion pack, the LED module and 3 cables.

Let’s do the following steps:

1. Grab 1 cable and connect the S pin of the LED module to the S0 pin of the expansion pack. Make sure that the cable is connected to the S0 position.
2. Next, grab another cable and connect the + pin of the LED module to the V1 pin of the expansion pack. This can be connected on any pin as long as it is a red pin of V1.
3. Finally, grab the last cable and connect the - pin of the LED module to the G pin of the expansion pack. This can be connected on any pin as long as it is a black pin of G.

You should have something like the picture below:

Software

Start a New Project and let’s call it “Conditionals”.

We are going to make a lantern that changes brightness when we press a button. We will turn on, turn off, and control the brightness with only 1 button!

Let’s use what we know from Analog Out and create a program that writes 1023 to P0:

Next, we will change the brightness to 0 when we press button A:

Let’s try the simulation… hmmm… it is not working???

Why is it not working? When we press button A, we change the value of P0 to 0 for a split second. However, the code in the forever block gets activated as soon as we pressed the button, which returns the value of P0 to 1023.

This is where variables come to the rescue!

We are going to save the value of brightness into a variable, so it doesn’t change suddenly.

Let’s create a variable called brightness. We are going to click on Make a Variable... from the Variables blocks.

You will see three new blocks. With the top most block, you can read the value of the variable. The middle one is to set the value of the variable to a specific number. The third one is to change the value by a certain amount.

Let’s grab our new blocks and place them in our code. First, when we press button A, we are going to set brightness to 0.

Then, we need to read the value of brightness in our forever block, so we know which brightness to use.

Finally, we will set the initial value of brightness to 1023. We do this by using the block on start.

We now have something like this:

Changing the brightness

Our program only works once. This is no good. How can we make it toggle the LED?

Here, we need to use conditionals. We are going to use the if <true▼> then (+) code block from Logic blocks.

We are going to set the brightness to 0 if its value is 1023, otherwise, we set it to 1023.

To do that, drag and drop the code block inside on button [A▼] pressed, and move the set block inside this conditional:

Then, click on the (+) button and let’s add a second set:

Finally, we are going to add the condition using the comparison code block from Logic blocks.

Drag and drop the first one <(0) [=▼] (0)> inside the <true▼> slot of the conditional:

Now, we just compare if brightness is equal to 1023:

Are you up for a challenge?

Try to make a program that turns on the LED when you press button A, turns off the LED when pressing the same button and can cycle through different brightness with the same button.

Once you finish, you can check your solution with the answer here.