C - Colour Mixing

Remember how each Sparkle contains 3 different colour LEDs?

We're going to make a program using variables, that allows you to change the Sparkle colour using the 2 buttons on the micro:bit.

Assemble your robot like the picture first!

Let's setup the start of our program.

We are going to need 3 variables this time - one for red, one for green, and one for blue

Add four new variables using the "Make a Variable" button in the variables menu.

Call them r, g and b (for red, green and blue), and one called sparkles for the neopixels.

We're going to use each of these variables to remember the amount of red, green and blue light we want.

In on start, setup the sparkles using the variable you just created. Make sure you set it to P0 with 9 LEDs.

We want to make sure we are continually updating the sparkles with the current values of r, g and b.

Add a block to the forever loop to do this, just like the picture.

We need to do one more thing before testing the program.

Before you use a variable in a program (like we have done in the Sparkle block), you need to set it equal to something - this is called initialisation.

Pull in three set blocks like the picture to initialise r,g, and b, in on start.

Set them equal to some different numbers - try it out and see what colours you get!

Now let's add some blocks to let us change the colour of the Sparkles using a button.

Inside the forever loop, add an If block that checks if button A is pressed.

If it is, change the r variable by 10.

Add a pause block of 200 milliseconds after r is increased. Otherwise, holding down the button will change r very quickly!

At the start of the program, set r, g and b to 0 again so you can see what is happening more clearly when testing your program.

In the picture are the blocks you need if you want a hint!

You probably noticed when testing your program that if you press the button enough times, the amount of red seems to start from zero again.

This is because the amount of red, green and blue in a Sparkle cannot be more than 255!

When r is more than 255 (when you have pressed the button more than 25 times), the Sparkle will show the value of r minus 255.

For example - 260 is more than 255, so the Sparkle will actually show 260-255=5!

We can now change the amount of red, but we want a colour mixer! Let's add another colour using the other switch.

Add another If block in the forever loop, that checks the second button (B) and increases g by 10 if it is pressed.

Don't forget to use another pause block!

There is another hint of the blocks required in the picture if you need some help.

Make sure to test your program properly before moving on. What do you notice when you add equal amounts of red and green?

You may have noticed that we have run out of buttons for the third colour, blue - but there is a solution!

What if we made a program that could increase b by 10 if both buttons are pressed at the same time?

To do this, inside the If block that checks button A, put an If/else block that checks button B.

If button B is pressed as well, increase b by 10 instead.

Else, just increase r by 10 as before.

Don't forget to wait 200 milliseconds!

There are some more hint blocks in the picture if you need them!

You've probably found the last program doesn't quite work correctly - if you press both buttons, the blue and green both increase!

This is because the second If block is still true if we are holding down both buttons, so g is also increased by 10.

Add an If/else block inside the second If block just like the one inside the first If block to fix this.

Have a look at the hint if you need to.

Congratulations - you have made a switch controlled colour mixer!

When r, g and b are all the same, the Sparkles will be white.

Add blocks to your program to:

Check if r, g and b are all the same (hint: you will need 3 If blocks inside each other, or you can use AND from the logic menu)

If they are, sound the buzzer!

You will also need to add the buzzer module.