Rainbow Colour Cycle

Part of the Outputs section of Coddy's Arduino journey. Lesson 8 of 24.

Every colour takes three digitalWrite() lines. A sequence of six colours would take 18 of them, and it is easy to mix up which line is which.

A function makes it short. setColor() takes one value for each colour and writes all three pins:

void setColor(int red, int green, int blue) {
  digitalWrite(redPin, red);
  digitalWrite(greenPin, green);
  digitalWrite(bluePin, blue);
}

Now each colour is one line, and its three values read like a recipe:

setColor(HIGH, HIGH, LOW);  // yellow
delay(500);

HIGH and LOW are the numbers 1 and 0, so they fit in an int parameter. Keep the parameters in the same order as you pass them: red, green, blue.

Challenge

Easy

Write setColor() and use it to show a rainbow, half a second per colour, again and again:

red
yellow
green
cyan
blue
magenta

Press Run, then Check.

Try it yourself

const int redPin = 11;
const int greenPin = 10;
const int bluePin = 9;

void setup() {
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);
}

void setColor(int red, int green, int blue) {
  // write each value to its pin
}

void loop() {
  setColor(HIGH, LOW, LOW);  // red
  delay(500);
  // then yellow, green, cyan, blue and magenta
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Outputs

Practice on your own: Arduino playground