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Arduino for beginners

Arduino for beginners – functions

by shedboy71 9th August 2016

written by shedboy71

When we create a function, it must be given a name. The naming convention for functions is the same as for variables:

•The function name can be made up of alphanumeric characters (A to Z; a to z; 0 to 9) and the underscore (_).
•The function name may not start with a number
•A function name must not be used that is the same as a language keyword or existing function.

A function must have a return type. If teh example function does not return anything, it will have a return type of void.

The function body is made up of a variety of statements placed between braces {}.

1) each function must have a unique name,
2) the function name is followed by parentheses ()
3) functions have a return type, e.g. void,
4) the body of a function is enclosed in opening and closing braces {}.

To call the function, you use the function name followed by opening and closing parentheses and then put a semi colon after it.

There are advantages of using functions is that they avoid having to write the same code over and over again. Every time you call a function, we are just reusing code that has been written once.

If you were to write code that say performed the same task 5 times then if you wished to update this for some reason you would have to modify the code in 5 places but if you were to use a function and call it 5 times then all you have to do is modify the function. Functions can be used to break a sketch up into pieces which make it easier to understand.

We are using the following circuit in the example later

Code Examples

We will take some of the code we created in previous tutorials and adapt this to use functions instead

[codesyntax lang=”cpp”]

int redled = 11;
int blueled = 10;
int greenled = 9;


void setup() 
{
pinMode(redled, OUTPUT); //set the LED pin as an output
pinMode(blueled, OUTPUT); //set the LED pin as an output
pinMode(greenled, OUTPUT); //set the LED pin as an output
}

void loop() 
{
int i = 1;
AllOff();
delay(1000);

while(i<=3)
{
switch (i) 
{
case 1:
RedOn();
delay(1000);
break;
case 2:
BlueOn();
delay(1000);
break;
case 3:
GreenOn();
delay(1000);
break;
default: 
break;
}
i++;
}
}

void AllOff()
{
digitalWrite(redled, HIGH); // red led off
digitalWrite(blueled, HIGH); //blue led off
digitalWrite(greenled, HIGH); //green led off
}

void RedOn()
{
digitalWrite(redled, LOW); // red led on
digitalWrite(blueled, HIGH); //blue led off
digitalWrite(greenled, HIGH); //green led off
}

void BlueOn()
{
digitalWrite(redled, HIGH); // red led off
digitalWrite(blueled, LOW); //blue led on
digitalWrite(greenled, HIGH); //green led off
}

void GreenOn()
{
digitalWrite(redled, HIGH); // red led off
digitalWrite(blueled, HIGH); //blue led off
digitalWrite(greenled, LOW); //green led on
}

[/codesyntax]

9th August 2016 0 comment

Arduino Basics

Arduino for beginners – setup and loop

by shedboy71 9th August 2016

written by shedboy71

The most basic Arduino sketch consists of two functions called setup() and loop(). The Arduino IDE once installed has a basic example that shows this. Open the Arduino IDE and select File → Examples → 01.Basics → BareMinimum to see the following in the IDE

[codesyntax lang=”cpp”]

void setup() {
// put your setup code here, to run once:

}

void loop() {
// put your main code here, to run repeatedly:

}

[/codesyntax]

The setup() function is called when a sketch starts. Use it to initialise variables, pins, start using libraries, etc. The setup function will only run once, after each power up or reset of the Arduino board.

Statements in the loop() function will run continuously from top to bottom and then back to the top. Lets you had 2 statements in your loop(), statement 1 would run first and then statement 2, once statement 2 had completed you would go back to statement 1 again and so on.

Code example

[codesyntax lang=”cpp”]

void setup() 
{
Serial.begin(9600);
Serial.println("*** We are in the setup loop ***");
delay(2000);
}

void loop() 
{
Serial.println("Now in main loop about to pause for 2 seconds.");
delay(2000);
Serial.println("This would be a statement or function");
delay(2000);
Serial.println("Arduino now at bottom of main loop.");
}

[/codesyntax]

Open the serial monitor and you should see the following, imagine these were different statements or functions that were running

*** We are in the setup loop ***
Now in main loop about to pause for 2 seconds.
This would be a statement or function
Arduino now at bottom of main loop.
Now in main loop about to pause for 2 seconds.
This would be a statement or function
Arduino now at bottom of main loop.
Now in main loop about to pause for 2 seconds.
This would be a statement or function
Arduino now at bottom of main loop.
Now in main loop about to pause for 2 seconds.
This would be a statement or function
Arduino now at bottom of main loop.
Now in main loop about to pause for 2 seconds.
This would be a statement or function
Arduino now at bottom of main loop.
As you can see the serial output in the setup() loop ran once and the other serial output will keep running and looping

9th August 2016 0 comment

Arduino Basics

Arduino for beginners – if / else statement

by shedboy71 9th August 2016

written by shedboy71

An if statement can be followed by an optional else statement, which executes when the expression is false.

Syntax

The syntax of an if…else statement is

[codesyntax lang=”cpp”]

if(expression) 
{
/* statement(s) will execute if the expression is true */
}
else 
{
/* statement(s) will execute if the expression is false */
}

[/codesyntax]
If the expression evaluates to true, then the if block will be executed, otherwise, the else block will be executed.

else can proceed another if test, so that multiple, mutually exclusive tests can be run at the same time.

Each test will proceed to the next one until a true test is encountered. When a true test is found, its associated block of code is run, and the program then skips to the line following the entire if/else construction. If no test proves to be true, the default else block is executed, if one is present, and sets the default behavior.

Note that an else if block may be used with or without a terminating else block and vice versa. An unlimited number of such else if branches is allowed.

Lets look at some examples

Code

[codesyntax lang=”cpp”]

void setup() 
{
int i = 1;

Serial.begin(9600);
while(i<=10)
{
if(i >=5 )
{
Serial.print("if (true) = ");
Serial.println(i);
}
else
{
Serial.print("else (false) = ");
Serial.println(i);
}
i++;
}
}

void loop() 
{
}

[/codesyntax]

Open the serial monitor and you will see the following

else (false) = 1
else (false) = 2
else (false) = 3
else (false) = 4
if (true) = 5
if (true) = 6
if (true) = 7
if (true) = 8
if (true) = 9
if (true) = 10
Lets look at en if / else if / else example

[codesyntax lang=”cpp”]

void setup() 
{
int i = 1;

Serial.begin(9600);
while(i<=30)
{
if(i >=1 && i <=10 ) //runs from 5 to 10
{
Serial.print("if = ");
Serial.println(i);
}
else if (i >=11 && i<=20) //runs from 11 to 20
{
Serial.print("elseif = ");
Serial.println(i);
}
else
{
Serial.print("else = "); // runs from 1 to 4
Serial.println(i);
}
i++;
}
}

void loop() {
}

[/codesyntax]

Open the serial monitor window

if = 1
if = 2
if = 3
if = 4
if = 5
if = 6
if = 7
if = 8
if = 9
if = 10
elseif = 11
elseif = 12
elseif = 13
elseif = 14
elseif = 15
elseif = 16
elseif = 17
elseif = 18
elseif = 19
elseif = 20
else = 21
else = 22
else = 23
else = 24
else = 25
else = 26
else = 27
else = 28
else = 29
else = 30

9th August 2016 0 comment

Arduino Basics

Arduino for beginners : if statement

by shedboy71 8th August 2016

written by shedboy71

if, which is used in conjunction with a comparison operator, tests whether a certain condition has been reached, such as an input being above a certain number.

If the expression evaluates to true, then the block of code inside the ‘if’ statement will be executed.

The syntax of the if statement is as follows:

if (expression > 50)
{
// do something here
}
The program tests to see if someVariable is greater than 50. If it is, the program takes a particular action. Put another way, if the statement in parentheses is true, the statements inside the brackets are run. If not, the program skips over the code.

The brackets may be omitted after an if statement. If this is done, the next line (defined by the semicolon) becomes the only conditional statement. The following examples are all valid ways of writing an if statement

[codesyntax lang=”cpp”]
if (x > 120) digitalWrite(LEDpin, HIGH);

if (x > 120)
digitalWrite(LEDpin, HIGH);

if (x > 120){ digitalWrite(LEDpin, HIGH); }

if (x > 120){
digitalWrite(LEDpin1, HIGH);
digitalWrite(LEDpin2, HIGH);
}
[/codesyntax]

I prefer the following approach, even if there was only statement to be executed, its only best to be consistent and use the same approach in all of your code.

[codesyntax lang=”cpp”]
if (x > 120)
{
digitalWrite(LEDpin1, HIGH);
}
[/codesyntax]

Code Examples

Lets look at a code example, this uses a while loop and will run 10 times. In our if statement we will only run the statements in the brackets which output via the serial monitor if the value of i is less than or equal to 5

[codesyntax lang=”cpp”]
void setup()
{
int i = 1;

Serial.begin(9600);
while(i<=10)
{
if(i <=5 )
{
Serial.print(“i = “);
Serial.println(i);
}
i++;
}
}

void loop() {
}
[/codesyntax]

In the serial monitor you will see the following

i = 1
i = 2
i = 3
i = 4
i = 5

You can use other comparison operators as well. Change the code to the following and run again. This one will only run the statements in the brackets if the value of i is equal to 5

[codesyntax lang=”cpp”]
void setup()
{
int i = 1;

Serial.begin(9600);
while(i<=10)
{
if(i ==5 )
{
Serial.print(“i = “);
Serial.println(i);
}
i++;
}
}

void loop() {
}
[/codesyntax]

This time in the serial monitor window you will see the following

i = 5

Now change the code to the following and run again. This one will only run the statements in the brackets if the value of i is greatr than or equal to 5

[codesyntax lang=”cpp”]
void setup()
{
int i = 1;

Serial.begin(9600);
while(i<=10)
{
if(i >=5 )
{
Serial.print(“i = “);
Serial.println(i);
}
i++;
}
}

void loop() {
}
[/codesyntax]

This time in the serial monitor window you will see the following

i = 5
i = 6
i = 7
i = 8
i = 9
i = 10

We have shown you some comparison operators above, here is a list of comparison operators you can use.
x == y (x is equal to y)
x != y (x is not equal to y)
x < y (x is less than y)
x > y (x is greater than y)
x <= y (x is less than or equal to y)
x >= y (x is greater than or equal to y)

Later on you will see that you can also use other operators such as boolean operators as well, here’s a taster

[codesyntax lang=”cpp”]
if (digitalRead(2) == HIGH && digitalRead(3) == HIGH)
{
//statements to be run here
}
[/codesyntax]

8th August 2016 0 comment

Arduino Basics

Arduino for beginners : do while loop

by shedboy71 8th August 2016

written by shedboy71

The do loop works in the same manner as the while loop, with one difference in that the condition is tested at the end of the loop, so the do loop will always run at least once even if the test expression was false.

The do while loop is shown below.

do {
Statement 1
Statement 2
…
} while (test expression);
Code Examples

OK, here is the standard do while equivalent of the previous for loop and while loop examples

[codesyntax lang=”cpp”]
void setup()
{
int i = 1;

Serial.begin(9600);

do
{
Serial.print(“i = “);
Serial.println(i);
i++;
}while(i<=10);
}

void loop() {
}
[/codesyntax]

Open the serial monitor window and you will see the following, looks good

i = 1
i = 2
i = 3
i = 4
i = 5
i = 6
i = 7
i = 8
i = 9
i = 10
Just for fun, lets remove the i++ from the code above and run again and look at the serial monitor window

i = 1
i = 1
i = 1
i = 1
i = 1
i = 1
i = 1
i = 1
i = 1
i = 1
i = 1
i = 1
i = 1

As you can see because the varable wasn’t incremented then the test expression will always be true , i will always be less than or equal to 10. Infinite loop.

Back to the RGB led again

Now lets repeat the fading an led and flashing an led 10 times examples

[codesyntax lang=”cpp”]
//change the brightness of an LED
int redled = 11;
int i =1;

void setup()
{
pinMode(redled, OUTPUT); //set the LED pin as an output
Serial.begin(9600);
do{
Serial.print(“loop = “);
Serial.println(i);
analogWrite(redled, i);
delay(10);
i++;
}while(i<=255);
}
void loop()
{
}
[/codesyntax]

Now flash the LED 10 times again

[codesyntax lang=”cpp”]
//flash the red led of the RGB led 10 times
int redled = 11;
int i = 1; //init the variable

void setup()
{
Serial.begin(9600);
pinMode(redled, OUTPUT); //set the LED pin as an output
//this will run 10 times
do
{
Serial.print(“loop = “);
Serial.println(i);
digitalWrite(redled, LOW); // led on
delay(500);
digitalWrite(redled, HIGH); //led off
delay(500);
i++; //dont forget this
}while(i<=10);
}

void loop()
{
}
[/codesyntax]

8th August 2016 0 comment

Arduino Basics

Arduino for beginners : while loop

by shedboy71 8th August 2016

written by shedboy71

while loops will loop continuously, and infinitely, until the expression inside the parenthesis, () becomes false. Something must change the tested variable, or the while loop will never exit. This could be in your code, such as an incremented variable, or an external condition, such as testing a sensor.
The while loop has a structure as follows:

while (test expression) {
Statement 1
Statement 2
…
}
test expression – a (boolean) C statement that evaluates to true or false

Lets look at some examples

Code Examples

[codesyntax lang=”cpp”]

void setup() 
{
int i = 1;

Serial.begin(9600);

while(i<=10)
{
Serial.print("i = ");
Serial.println(i);
i++;
}
}

void loop() {
}

[/codesyntax]

Open the serial monitor and you should see the following

i = 1
i = 2
i = 3
i = 4
i = 5
i = 6
i = 7
i = 8
i = 9
i = 10

As you can see we set the variable to 1, we then test whether the variable is less than or equal to 10. If it is not then the statements will run in the brackets which is basically outputing this value via the serial monitor. Important part is that we increment the variable using i++.

This increments the value of the variable by 1, this is the same incidentally as writing i = i + 1; which is sometimes used as well. Forgetting this would cause the while loop to always run – an infinite loop. You can remove the i++ and see what happens.

Now back to the RGB led example

Now lets fade that led again like in the for loop example

[codesyntax lang=”cpp”]

//change the brightness of an LED
int redled = 11;
int i =0;

void setup()
{
pinMode(redled, OUTPUT); //set the LED pin as an output
Serial.begin(9600);
while(i<=255)
{
Serial.print("loop = ");
Serial.println(i);
analogWrite(redled, i);
delay(10);
i++;
} 
}

void loop()
{
}

[/codesyntax]

Lets flash that red led 10 times again

[codesyntax lang=”cpp”]

//flash the red led of the RGB led 10 times
int redled = 11;
int i = 1; //init the variable

void setup()
{
Serial.begin(9600);
pinMode(redled, OUTPUT); //set the LED pin as an output
//this will run 10 times
while(i<=10)
{
Serial.print("loop = ");
Serial.println(i);
digitalWrite(redled, LOW); // led on
delay(500);
digitalWrite(redled, HIGH); //led off
delay(500);
i++; //dont forget this
} 
}

void loop()
{
}

[/codesyntax]

8th August 2016 0 comment