Tune LED Colors with Button

For this project, you’ll use three inputs to affect three outputs. Each button will change the brightness of an LED. Since each input does the same thing for its respective output, we will use a function to save some repetition in the code.

Code

/* * Tune a multicolor LED's colors with buttons * The analogWrite() function works on digital pins 3,5,6,9,10,11. */ int brightness; //holds the brightness of the outputs. Range is 0-255 //function that takes in the pin number and changes brightness on that pin void changeBrightness(int _pin){//'pass in' a pin number to the function brightness++; //increase the brightness variable by one analogWrite(_pin,brightness); //write 'brightness' to the pin you passed in. if(brightness == 255){ //reset brightness to 0 if it reaches max (255) brightness = 0; } } void setup(){ //Set all LEDS to output pinMode(9,OUTPUT); pinMode(10,OUTPUT); pinMode(11,OUTPUT); //one button per LED color pinMode(A5, INPUT_PULLUP); pinMode(A1, INPUT_PULLUP); pinMode(2, INPUT_PULLUP); } void loop(){ /* * When a button is held down, pass the corresponding LED pin number * to the function over and over again */ if(digitalRead(A5) == LOW){ changeBrightness(9); //pass the LED pin number to the function } else if(digitalRead(A1) == LOW){ changeBrightness(10); } else if(digitalRead(2) == LOW){ changeBrightness(11); } delay(10); //Speed of fade while button is LOW. Longer delay = slower fade } // (c) 2017 Let's Start Coding. License: www.letsstartcoding.com/bsdlicense

Challenges

How many can you complete? Change the code and hardware according to the challenges below. Upload your code to see the effect when you're finished. Complete a challenge? Check it off the list!

Create a reset button that sets all of the brightness levels back to 0 when you push it.
Use pinMode and digitalWrite commands and an 'if' statement.

Change the delay(10); to delay(0); .

Add another multicolor LED to ports 5,6 (leave one leg sticking out) and add the pins to the code with pinMode().
Add in some function calls to changeBrightness with your new pins to see what happens.

Create a new decreaseBrightness function that decreases the brightness of one of your LEDs when a button is pressed.
Copy the format of the example function, but change the name and change brightness++ to brightness--.
Then add a new 'if' statement to the program that has the logic "if button pressed, decreaseBrightness(pinNumber)".

Videos

Read the Code Walkthrough Text (click to open)

First, you create a variable to hold the brightness value of your outputs, since that will be changing as the button is held down to ‘tune in’ a specific color. Brightnesses can range from 0 to 255.

Next, you define a new function. A function is a cluster of code that always runs together. It can do a set of tasks, run a calculation and spit out the answer, check the status of an input, or change the brightness of an LED, like it does here. The purpose of creating this function is that you want to do the exact same thing each time you press a button- change the brightness of an LED. The only thing that changes is which LED and which button.

Because your function here does a set task with no output, you start by declaring it 'void'.

Next, you name the function. Like a variable, you should name it something that is easy to remember and understand.

The next part of the function is to define what information the function needs in order to do its job. Within the parentheses of the function, you define what types of variables or values can be fed into the function. These are the arguments for the function. In this function, you're allowing one integer to be passed in. The function doesn't know what number will be passed to it. You create a variable called _pin that will hold the value of whatever number you give to the function. The underscore before the variable name is a naming convention for function-argument variables.

To look at it another way, when you create (int _pin) as a function argument, you're saying "an integer called _pin will equal whatever number is passed to the function. It will hold that value for one run of the function.".

Once the function is called (passed an int), it will increase the brightness variable by one, then analogWrite() brightness to the pin number that was passed in.

Next, it checks the ‘if’ to find out if the brightness variable should be reset. After that, the function is complete and the computer jumps back to the loop just below where the function was called.

After setting up each pin as an INPUT_PULLUP (buttons) or OUTPUT (LEDs), the job of the void loop is to check each button status and call the function.

The if statement checks to see if button A5 is pressed. If it is, the only action of the if statement is to send the number 9 (the LED pin) to the function. The function is called by typing its name and then giving it whatever arguments it needs. What happens next is that the computer jumps to the function and gives it the pin number. The function uses that pin number as the variable _pin and runs its task- changing the brightness and checking for a 'brightness reset'.

Once the function is complete, the computer jumps back down to the delay in the void loop- all of the else if statements are skipped because the if statement is true.

The loop starts over. Imagine now that the button on A5 is not pressed. The computer will pass over that code and to the else if(digitalRead(A1...... statement. If that statement is true, changeBrightness() is called again, but with the number 10 used for the _pin variable.

The void loop runs once every time the function is run, jumping back and forth between the function and the void loop.

Concepts

New Concept: Creating Functions

Functions are groups of code that run together. You use functions every time you write one of our programs- void setup() and void loop() are functions. When you're programming, you're filling out the contents of those functions.

When you use a function like digitalWrite() or tone(), you don't see the contents of the function, but you're using it by passing it arguments.

You can create your own functions in order to make your programs simpler. They're a labeled group of commands that you can use at any point in a program. If you find yourself repeating the same statements multiple times within a program, consider making a function out of those commands.

You should place your function outside of the void setup() and the void loop() functions. Put the function at the very top of your code.

The first word in creating a function is its type. A void function simply does the code between the function's curly braces- it doesn't send a value back to the code. If you have a function that does a math equation, you may create an int function that can send a number back to the code and be used by the rest of the program.

The second word in the function is its name. It's best to name a function clearly so that you know what its job is.

The third part of the function is to define the arguments that the function requires to work. Not all functions require an input- they simply do their job when called. It's up to you to decide what information your function requires. When creating an argument for your function, you define what type of value it will be - int is usually fine for numbers. Then you create a name for that argument. This is the name you'll use for that value throughout the rest of the function.

To require another argument, just type a comma, the next argument's type, and the next argument's name. You can require many arguments for a function to work, but it's recommended to keep the number low (3 or fewer) for simplicity. You can also create optional arguments, meaning that the argument will have a default value unless you call the function with that value changed. Optional parameters are a more advanced topic.

After you've defined the type, name, and requirements of the function, you type an opening curly brace and then start typing the code that your function will run when called. When you want to use the value of the arguments that the computer passed your function, you type the name of the argument that you put in the parentheses.

For example, if you had a function that set pinMode to OUTPUT for any number you passed it, you might have:

void pinOut (int _pinNum){

pinMode(_pinNum, OUTPUT);

}

That's not a very useful function (pinMode() is a function, too!), but it would work.

Functions can contain if statements, loops, variables, and calls to other functions. They can contain a program that takes an hour to run- anything you define in between the curly braces. Once you've defined what your function will do, you can close the curly braces.

To make your function run, you have to call it. That is, you have to tell it to run and give it any information it requires in order to work. To call a function, you type its name and an open parentheses, the value you want to pass the function, and then a closing parentheses and a semicolon.

A call to the pinOut function may look like:

pinOut(9);

There are multiple errors that can occur when you are using a function. For example, if you pass the function the wrong type of information, too much information, or too little information, it won't know what to do with that information and your code won't run.

Functions are very useful in breaking up more complex code into separate pieces that can run alone.

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