Dice Roll

To create a rolling die with a button and a single LED, you need to trigger a random event with your input and then show the outcome with your output. The dice can have 6 possible positions, so using blinks on the one LED can show the outcome of the ‘roll’.

Code

/* * Press a button to 'roll a die' and get the outcome in blinks. * Placing loops inside loops is called 'nesting'. */ void setup() { pinMode(11,OUTPUT);//LED pinMode(A5,INPUT_PULLUP);//button } void loop() { //While the button is held down, 'roll the dice' by flickering the LED while(digitalRead(A5) == LOW){ digitalWrite(11,HIGH); delay(50); digitalWrite(11,LOW); delay(50); if(digitalRead(A5)==HIGH){ //if the button is released delay(500); //choose a random number 1-6 and blink the LED that number of times for(int blinks = 0; blinks<= random(1,7); blinks++){ digitalWrite(11,HIGH); delay(300); digitalWrite(11,LOW); delay(300); } //close the 'for' loop } //close the 'if' statement } //close the 'while' loop } //close the 'void loop' // (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!

Change <=random(1,7) to <=random(1,21) for a 20-sided dice.

Try to add a tone that rises while the button is held down. You'll need a new variable, a pinMode() command for the speaker, and a bunch of experimentation!

Can you convert the dice so that it 'beeps' out the count with a speaker instead of an LED? Replace the LED with a speaker.

Can you add another LED so that your project rolls two 'dice' at once? You'll need another 'for' loop for your LED just below the 'for' loop in the example.

Videos

Read the Code Walkthrough Text (click to open)

The void loop of this code contains loops within loops. Pay close attention to the indentation and styling of the code- it becomes more important with complex programs like this.

The first line within void loop is a while loop. The while loop runs under one condition: if digitalRead(2) == LOW. The while loop will continue to repeat as long as the condition is true, whether that is one second or one hundred years. While a while loop is running, the rest of the loop outside of it is not checked. That is an important difference between a while loop and an if statement.

Notice that the rest of this code is inside this while loop. You have not yet reached its closing curly brace.

While the condition of the while loop is true, the LED light flickers on and off rapidly with the four lines of digitalWrite() and delay. The if statement inside the while loop is checked, but as long as it is false, the flickering of the light will continue.

The if statement will become true if the button is released, sending a HIGH signal to Maker Board. If that condition is true, there is a delay of half a second and then the for loop begins.

Notice that the for loop is inside the if statement.

The for loop creates a variable called blinks and gives it a value of 0. The condition for this for loop contains a function: random. The random function takes in two values and returns a value between the first number and the higher number, not including the highest number. Here, that means that the condition to keep running the for loop can be:

blinks <=1;

blinks<=2;

blinks<=3;

blinks<=4;

blinks<=5;

blinks<=6;

You won't know what the random value will return- that's what makes it a good dice!

The last condition of the for loop instructs the blink count to increase each time the for loop runs.

The action of the for loop is to blink the light, showing your result.

The closing curly braces are commented in this code to help you keep track of them. First, you end the for loop's action. Then, you close the if statement, then the while statement, then the void loop.

If you really think about and experiment with this program, you'll see why it has to be structured this way. If the if statement was not inside the while loop, it would run all of the time (an unpressed button sends a HIGH signal). If the for loop wasn't inside the if statement, the dice result would blink each time the while loop ran.

Concepts

Special note about this program

In the example above, you can replace the while with an if statement- just delete 'while' and type 'if'. To complete the code challenge of adding a tone to the program while the dice is being shaken, you need a while loop if you want to declare your pitch variable within the loop.

Why? When you declare a variable, it sets that variable's value. A variable declared at the top of the loop will be re-declared every time the loop runs. An if statement will continue to run the entire loop as the dice is 'shaken', result in constantly redeclaring the variable. In short, the tone won't ever rise.

A while loop, though, does not run the entire void loop while it's condition is true- it only runs the while loop. Therefore, a while loop can increase a variable even if that variable is declared in the void loop.

This is a good example of different approaches to the same result- you can also solve the challenge without a while loop- you just have to think creatively!

New Concept: While Loops

A while loop has one condition and a set of actions that happen when that condition is true. A while loop repeats until the condition between the parentheses is false. This statement is most useful when you're not sure what values will be in the condition.

The if statement and while loop are closely related and often interchangeable. There are some characteristics of a while loop, though, that make it unique and useful. The while loop doesn't check any conditions outside itself once it has started.

For example, in an earlier program, you could hold down a button to raise the tone on a speaker. When you released the button, the tone would fall. What if you wanted to ensure the tone went all the way to its minimum before it could rise again? That is difficult with an if statement. Whenever you press the button, the if statement will trigger and the tone will rise. With a while loop, that if statement is not checked until the while loop is complete. Using a while loop, your code would follow the logic: if button pressed, raise tone. Else, while the tone is above the minimum level, bring it down to the minimum level. The while loop cannot be interrupted by an outside line of code.

While loops are also good to use when you're not sure the starting point of a loop. With a for loop, you define how many times it will run. With a while loop, it will continue until the condition is false. Using the earlier example, imagine someone held the button down until the tone was at 2000 hertz. To get back to 0 hertz in steps of one, the while loop needs to run 2000 times. Now imagine that someone held the button down until the tone was at 100 hertz. Now the while loop only needs to run 100 times to bring the sound back to 0. You don't have to define the number of times a while loop needs to run.

New Concept: Nesting Statements

There aren't that many building blocks to most programs- loops, statements, variables, conditionals- but they can be combined in infinite ways. When a code statement is run inside another code statement, that is called nesting one statement inside another. The more decisions that are based on each other in a program, the more complex nesting can get.

Nesting is necessary for some programs, but there are tips that can help you keep track of your logic and code. Indentation is one of them. You can think of most of your program's code as nested inside the void loop(). That's why the code inside void loop is indented by one tab. When you create an if statement, the action of the statement should be indented one tab further than the if statement. When your if statement contains a for statement, it should be indented by one more tab than the if statement.

In general, code indented further to the right on your screen depends on many things happening before it will run.

When you create a new statement that doesn't depend on the code above it to run, remove indentations until that line is indented one tab further than the line it depends upon.

You will see some programs that are poorly indented and they are very hard to follow. Try your best to keep up with your indentation to be a clear programmer.

You should also indent the closing curly braces of your statements to the same level as the word beginning that statement. For example, the closing curly brace of an if statement should always line up vertically with the letter 'i' that starts the if statement. The closing curly brace of a for loop should line up vertically with the letter 'f' that starts the loop.

This technique will keep your code easy to read and change. You can trace a vertical line from any closing curly brace up to the statement it closes. If you have many closing curly braces, it may even be a good idea to comment them so you know what they close.

Nesting is purely stylistic- it doesn't matter to the computer if you nest your code or not. However, it's a practice that can save you many hours of frustration if you learn to use it.

New Concept: random() Function

The random function is built in to the Arduino software and there is some variety of it available in most programming languages. Give the random() function two numbers and it will return a number between those two numbers. The random function includes the lowest number you provide and excludes the highest number you provide, so keep that in mind.

To use the random() function, place it wherever in the code you want the random value. Imagine that "random(x,y)" will be replaced with a number between x and y.

Quiz

If you're having trouble, try to run a program that can help you find the answer.

1.What are the possible numbers that random(1,5) could return?

0-5
1-5
0-4
1-4

2. When you create code statements inside other code statements, what is that called?

Egging
Nesting
Stacking
Enclosing

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