Category:

Arduino Basics

Arduino for beginners : Define

by shedboy71 12th August 2016

written by shedboy71

WARNING: Preprocessor macros, although tempting, can produce quite unexpected results if not done right. Always keep in mind that macros are textual substitutions done to your source code before anything is compiled. The compiler does not know anything about the macros and never gets to see them. This can produce obscure errors, amongst other negative effects. Prefer to use language features, if there are equivalent (In example use const int or enum instead of #defined constants).

That said, there are cases, where macros are very useful (see the debug macro below for an example).

The #define directive is used to define values or macros that are used by the preprocessor to manipulate the program source code before it is compiled. Because preprocessor definitions are substituted before the compiler acts on the source code, any errors that are introduced by #define are difficult to trace.

By convention, values defined using #define are named in uppercase. Although doing so is not a requirement, it is considered very bad practice to do otherwise. This allows the values to be easily identified when reading the source code.

Today, #define is primarily used to handle compiler and platform differences. E.g., a define might hold a constant which is the appropriate error code for a system call. The use of #define should thus be limited unless absolutely necessary; typedef statements and constant variables can often perform the same functions more safely.

In the Arduino world you commonly see #define used when you are setting up I/O pins for sensors, LEDs and other tasks. Lets look at an example

[codesyntax lang=”cpp”]

void setup()
{
pinMode(11, OUTPUT); //set the LED pin as an output
pinMode(10, OUTPUT); //set the LED pin as an output
pinMode(9, OUTPUT); //set the LED pin as an output
}

[/codesyntax]

Then in the loop you may have

digitalWrite(11, HIGH); // red led off

The code above is perfectly valid and will work but the problem is that it’s not overly clear what these are used for and if you had numerous pins used it could quickly get confusing. Instead you could do the following

[codesyntax lang=”cpp”]

#define redled 11
#define blueled 10
#define 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
}

[/codesyntax]

Then in the loop you may have

digitalWrite(redled, HIGH); // red led off

That looks a lot better to me

12th August 2016 0 comment

Arduino Basics

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

Arduino Basics

Arduino for beginners : for loops

by shedboy71 8th August 2016

written by shedboy71

Arduino for beginners : for loops

The for statement is used to repeat a block of statements enclosed in curly braces. An increment counter is usually used to increment and terminate the loop. The for statement is useful for any repetitive operation, and is often used in combination with arrays to operate on collections of data/pins.
There are three parts to the for loop:

for (initialization; condition; increment)
{
//statement(s);
}

The initialization happens first and exactly once. Each time through the loop, the condition is tested; if it’s true, the statement block, and the increment is executed, then the condition is tested again. When the condition becomes false, the loop ends.

Code Examples

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

Serial.begin(9600);

for (i = 0; i < 10; i++)
{
Serial.print(“i = “);
Serial.println(i);
}
}

void loop() {
}
[/codesyntax]

Open the serial monitor and you should see the following output

i = 0
i = 1
i = 2
i = 3
i = 4
i = 5
i = 6
i = 7
i = 8
i = 9

In these examples we will connect an RGB led to our Arduino, this will be used in several examples. Here is a breadboard layout and schematic, we used a common anode type

We will only use the red led of the RGB led in these examples

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

void setup()
{
pinMode(redled, OUTPUT); //set the LED pin as an output
Serial.begin(9600);
for (int i=1; i <= 255; i++)
{
Serial.println(“loop = “);
Serial.println(i);
analogWrite(redled, i);
delay(10);
}
}

void loop()
{
}

[/codesyntax]

As this is in the setup() it will only run once, changing this to the loop() will mean the led continuously runs through the for loop and fading the LED

[codesyntax lang=”cpp”]

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

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

void loop()
{
for (int i=1; i <= 255; i++)
{
analogWrite(redled, i);
delay(10);
}
}

[/codesyntax]

In this example we will flash the red of an RGB led on and off 10 times

[codesyntax lang=”cpp”]

//flash the red led of the RGB led 10 times
int redled = 11;

void setup()
{
Serial.begin(9600);
pinMode(redled, OUTPUT); //set the LED pin as an output
//this will run 10 times
for (int i=1; i <= 10; i++)
{
Serial.print("loop = ");
Serial.println(i);
digitalWrite(redled, LOW); // led on
delay(500);
digitalWrite(redled, HIGH); //led off
delay(500);
} 
}

void loop()
{
}

[/codesyntax]

8th August 2016 0 comment

Arduino Basics

Random function example

by shedboy71 12th November 2015

written by shedboy71

In this example we use the RGB led again but are introducing a couple of new programming topis. We introduce the switch case structure and the random and randomSeed functions. We are using the same circuit as before, here it is as a reminder

RGB to ARduino

The following is from the reference documentation, rather than rewrite the wheel here is an explanation.

The switch…case controls the flow of programs by allowing programmers to specify different code that should be executed in various conditions. In particular, a switch statement compares the value of a variable to the values specified in case statements. When a case statement is found whose value matches that of the variable, the code in that case statement is run.

The break keyword exits the switch statement, and is typically used at the end of each case. Without a break statement, the switch statement will continue executing the following expressions (“falling-through”) until a break, or the end of the switch statement is reached.

randomSeed() initializes the pseudo-random number generator, causing it to start at an arbitrary point in its random sequence. This sequence, while very long, and random, is always the same.

If it is important for a sequence of values generated by random() to differ, on subsequent executions of a sketch, use randomSeed() to initialize the random number generator with a fairly random input, such as analogRead() on an unconnected pin.

The random function generates pseudo-random numbers.

Lets look at the example, we will generate a random number from 0 to 6 (remember the random number starts at 0 unless you state a min and max number), the randomSeed to help generate a truely random number and a switch case to flash the RGB led in a particular sequence

Code

[codesyntax lang=”cpp”]

int redPin = 11;
int greenPin = 10;
int bluePin = 9;
 
 
void setup()
{
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);  
  randomSeed(analogRead(0));
}
 
void loop()
{
  int randColour = random(7);
  switch(randColour)
  {
    case 0 :  setColour(0, 255, 255); 
              delay(1000);
              break;
    case 1 :  setColour(255, 255, 0); 
              delay(1000);
              break;   
    case 2 :  setColour(255, 0, 255);  
              delay(1000);
              break; 
    case 3 :  setColour(0, 255, 255); 
              delay(1000);
              break;   
    case 4 :  setColour(255, 0, 0); 
              delay(1000);
              break;  
    case 5 :  setColour(0, 0, 0); 
              delay(1000);
              break;   
    case 6 :  setColour(128, 128, 128); 
              delay(1000);
              break;  
    default:  setColour(255, 255, 255); 
              delay(1000);
              break;               
  }

}
 
void setColour(int red, int green, int blue)
{
  analogWrite(redPin, red);
  analogWrite(greenPin, green);
  analogWrite(bluePin, blue);  
}

[/codesyntax]

12th November 2015 0 comment

Arduino Basics

Basic RGB LED example

by shedboy71 12th November 2015

written by shedboy71

An RGB led is basically 3 LEDs in the one package, a red, green and blue one which either share a common cathode or a common cathode. Using one of these LEDs you can create a variety of different colours simply by switching on and off various LEDs, PWM which we will discuss later also works well here. Lets look at an RGB LED

rgb led pinout

You will need the following, I used a low cost RGB LED breakout.

1 Arduino UNO
1 RGB LED
1 1k resistor
Some connection wire
1 Breadboard

The connection is fairly straightforward we simply connect the common anode to VCC via the resistor and the cathodes are connected to 3 digital pins , you can see these clearly in the code example below

[codesyntax lang=”cpp”]

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

[/codesyntax]

Here is the schematic

RGB to ARduino

Now as this is a common anode type, a high on the digital pin will switch the LED off and a low will switch the LED on. If you had a common cathode you would need to reverse the values. Lets show you what I mean.

We use the following

[codesyntax lang=”cpp”]

setColour(0, 255, 255); // red

[/codesyntax]

Which in turn calls the following function

[codesyntax lang=”cpp”]

void setColour(int red, int green, int blue)
{
analogWrite(redPin, red);
analogWrite(greenPin, green);
analogWrite(bluePin, blue); 
}

[/codesyntax]

As you can see from the example above the red LED is on (low), the green and blue LED is off. So you will see red. You can in fact put a variety of values in to see different colours on the RGB led

Code

[codesyntax lang=”cpp”]

int redPin = 11;
int greenPin = 10;
int bluePin = 9;
 
 
void setup()
{
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);  
}
 
void loop()
{
  setColour(0, 255, 255);  // red
  delay(1000);
  setColour(255, 0, 255);  // green
  delay(1000);
  setColour(255, 255, 0);  // blue
  delay(1000);
  setColour(0, 80, 0);  // purple
  delay(1000);
  setColour(255, 0, 0);  // aqua
  delay(1000);
  setColour(0, 0, 0);  // white
  delay(1000);
}
 
void setColour(int red, int green, int blue)
{
  analogWrite(redPin, red);
  analogWrite(greenPin, green);
  analogWrite(bluePin, blue);  
}

[/codesyntax]

Links
10PCS/LOT WS2812 RGB LED Breakout Module For Arduino

100 x Emitting Diodes RGB Led 5mm led diode

12th November 2015 0 comment

Arduino Basics

Using loops for the LED examples

by shedboy71 12th November 2015

written by shedboy71

In the last example – http://www.mikroblog.net/arduino/arduino-basics/more-arduino-and-led-examples.php we showed you some examples of flashing multiple LEDs, now this code worked OK but there is a more efficient way of doing the same action. We use loops to initialize the LEDs and then again for switching the LEDs on and off. There are 3 different types of loop and we will show the same example for all 3 of them.

Parts List

1 x Arduino UNO
7 x Leds
7 x 220ohm resistors

Schematic

Example 1 : Use a for loop to initialize the pins as outputs and also cycle through the LEDs one at a time from 2 to 8
[codesyntax lang=”cpp”]

#define myDelay 500

void setup() 
{
// initialize the digital pins as outputs:
for (int i = 2; i<=8 ; i++) 
{
pinMode(i, OUTPUT);
}
}

void loop() 
{
for (int i = 2; i<=8; i++) 
{ // blink LEDs on pins 2 to 8
digitalWrite(i, HIGH);
delay(myDelay);
digitalWrite(i, LOW);
}
}

[/codesyntax]

Example 2 : reverse it, going from 8 to 2

[codesyntax lang=”cpp”]

#define myDelay 500

void setup() 
{
// initialize the digital pins as outputs:
for (int i = 2; i<=8 ; i++) 
{
pinMode(i, OUTPUT);
}
}

void loop() 
{
for (int i = 8; i>=2; i--) 
{ // blink from LEDs 8 to 2
digitalWrite(i, HIGH);
delay(myDelay);
digitalWrite(i, LOW);
}
}

[/codesyntax]

Example 3 : You can also use a Do While loop, here is the example above again. the concept again is simple we set the variable i to be 8, we then decrement this (subtract) by 1 every time. When i is equal to 2 the loop will exit and start again at 8.

[codesyntax lang=”cpp”]

#define myDelay 500

void setup() 
{
// initialize the digital pins as outputs:
for (int i = 2; i<=8 ; i++) 
{
pinMode(i, OUTPUT);
}
}

void loop() 
{
int i = 8;
do{
digitalWrite(i, HIGH);
delay(myDelay);
digitalWrite(i, LOW);
i--;
}while(i>=2);
}

[/codesyntax]

Example 4 : A while loop this time, same concept as above.

[codesyntax lang=”cpp”]

#define myDelay 500

void setup() 
{
// initialize the digital pins as outputs:
for (int i = 2; i<=8 ; i++) 
{
pinMode(i, OUTPUT);
}
}

void loop() 
{

int i = 8;

while(i>=2)
{
digitalWrite(i, HIGH);
delay(myDelay);
digitalWrite(i, LOW);
i--;
}
}

[/codesyntax]

12th November 2015 0 comment

Arduino Basics

More Arduino and LED examples

by shedboy71 12th November 2015

written by shedboy71

In the first basic tutorial we showed a couple of simple LED examples, here is another couple to try

A reminder of the schematic if you need it

Arduino and LEDs

Code examples
Start up the Arduino IDE, a barebones sketch will appear, delete everything and enter the following

Example 1: Leds on and off – one at a time

[codesyntax lang=”cpp”]

/*
* Blink many LEDs example
* switches an LED on and off one at a time
*/
void setup() 
{
pinMode(2, OUTPUT); // set pin 2 as output
pinMode(3, OUTPUT); 
pinMode(4, OUTPUT); 
pinMode(5, OUTPUT); 
pinMode(6, OUTPUT); 
pinMode(7, OUTPUT); 
pinMode(8, OUTPUT); 
}

void loop() 
{
digitalWrite(2, HIGH);
delay(1000);
digitalWrite(2, LOW); 
delay(1000);
digitalWrite(3, HIGH); 
delay(1000);
digitalWrite(3, LOW); 
delay(1000);
digitalWrite(4, HIGH); 
delay(1000);
digitalWrite(4, LOW); 
delay(1000);
digitalWrite(5, HIGH); 
delay(1000);
digitalWrite(5, LOW); 
delay(1000);
digitalWrite(6, HIGH); 
delay(1000);
digitalWrite(6, LOW); 
delay(1000);
digitalWrite(7, HIGH); 
delay(1000);
digitalWrite(7, LOW); 
delay(1000);
digitalWrite(8, HIGH); 
delay(1000);
digitalWrite(8, LOW); 
delay(1000);
}

[/codesyntax]
Example 2: Switch the LEDs on one a time and then off again

[codesyntax lang=”cpp”]

/*
* Blink many LEDs example
* switches an LED on one at a time then off one at a time
*/
void setup() 
{
pinMode(2, OUTPUT); // set pin 2 as output
pinMode(3, OUTPUT); 
pinMode(4, OUTPUT); 
pinMode(5, OUTPUT); 
pinMode(6, OUTPUT); 
pinMode(7, OUTPUT); 
pinMode(8, OUTPUT); 
}

void loop() 
{
digitalWrite(2, HIGH);
delay(1000);
digitalWrite(3, HIGH);
delay(1000);
digitalWrite(4, HIGH); 
delay(1000);
digitalWrite(5, HIGH); 
delay(1000);
digitalWrite(6, HIGH); 
delay(1000);
digitalWrite(7, HIGH); 
delay(1000);
digitalWrite(8, HIGH); 
delay(1000); 
digitalWrite(2, LOW);
delay(1000);
digitalWrite(3, LOW);
delay(1000);
digitalWrite(4, LOW); 
delay(1000);
digitalWrite(5, LOW); 
delay(1000);
digitalWrite(6, LOW); 
delay(1000);
digitalWrite(7, LOW); 
delay(1000);
digitalWrite(8, LOW); 
delay(1000); 
}

[/codesyntax]

Example 3 : All on the All off

[codesyntax lang=”cpp”]

/*
* Blink many LEDs example
* switches all LEDs on then off
*/
void setup() 
{
pinMode(2, OUTPUT); // set pin 2 as output
pinMode(3, OUTPUT); 
pinMode(4, OUTPUT); 
pinMode(5, OUTPUT); 
pinMode(6, OUTPUT); 
pinMode(7, OUTPUT); 
pinMode(8, OUTPUT); 
}

void loop() 
{
digitalWrite(2, HIGH);
digitalWrite(3, HIGH);
digitalWrite(4, HIGH); 
digitalWrite(5, HIGH); 
digitalWrite(6, HIGH); 
digitalWrite(7, HIGH); 
digitalWrite(8, HIGH); 
delay(1000); 
digitalWrite(2, LOW);
digitalWrite(3, LOW);
digitalWrite(4, LOW); 
digitalWrite(5, LOW); 
digitalWrite(6, LOW); 
digitalWrite(7, LOW); 
digitalWrite(8, LOW); 
delay(1000); 
}

[/codesyntax]

Of course there are better ways of doing the examples above, we will show you these soon

12th November 2015 0 comment

Arduino Basics

Arduino and LEDs example

by shedboy71 12th November 2015

written by shedboy71

Flashing an LED is one of the most basic projects to get started with when learning about the Arduino platform, in this example we will use 8 LEDs. This is for future examples as well, we also used red, yellow and green colours (UK traffic lights) but again this is user preference. There is an onboard LED and resistor connected to Pin 13 but I’d rather go to a tiny bit of effort and either use an external resistors and LEds on a breadboard or as i tend to do I create little prototype boards with basic electronic circuits on them, you’ll see this in a photograph later of the test board I have

You will need the following, I recommend purchasing one of the basic arduino starter kits (link at the bottom) which usually contain an Arduino Uno, a breadboard and a few electronic components like resistors, LEDs, capacitors, transistors to get you going

Parts List

1 x Arduino UNO
8 x Leds
8 x 220ohm resistors
Connecting cables
Breadboard – if required

Schematic

Here is the schematic, as you can see we used digital pins 2 to 9

Arduino and LEDs

In the picture below you can see our Arduino Uno (with a sensor shield fitted) connected to a prototyping board with the resistors and LEDs fitted and all connections made

Arduino and LEDs

Code examples

The setup() function is called when a sketch starts. Use it to initialize variables, pin modes, start using libraries, etc. The setup function will only run once, after each powerup or reset of the board.

After creating a setup() function, the loop() function does precisely what its name suggests, and loops consecutively, allowing your program to change and respond as it runs. Code in the loop() section of your sketch is used to actively control the board.

In the example below we will initiliaze the 2 as an output pin, then in the loop we will toggle the led high (the led lights), delay for 1000 milliseconds, toggle the led low (the led does not light) and then delay again. Since this is in the loop theis will run continously.

Start up the Arduino IDE, a barebones sketch will appear, delete everything and enter the following

[codesyntax lang=”cpp”]

/*
* Blink an LED example
* by mikroblog
*/
void setup() 
{
pinMode(2, OUTPUT); // set pin 2 as output
}

void loop() 
{
digitalWrite(2, HIGH); // set pin 2 as high or 1
delay(1000); // 1 second delay
digitalWrite(2, LOW); // set pin 2 as low or 0
delay(1000); // 1 second delay
}

[/codesyntax]

Now you can switch 2 LEDs on at the same time as follows

[codesyntax lang=”cpp”]

/*
* Blink an LED example
* by mikroblog
*/
void setup() 
{
pinMode(2, OUTPUT); // set pin 2 as output
pinMode(3, OUTPUT); // set pin 2 as output
}

void loop() 
{
digitalWrite(2, HIGH); // set pin 2 as high or 1
digitalWrite(3, HIGH); // set pin 2 as high or 1
delay(1000); // 1 second delay
digitalWrite(2, LOW); // set pin 2 as low or 0
digitalWrite(3, LOW); // set pin 3 as low or 0
delay(1000); // 1 second delay
}

[/codesyntax]

In later exercises we will go through some other examples, these are quite basic but can be useful for learning basic programming techniques such as loops

Links
Ultimate Starter Kit for Arduino 1602 LCD Servo Motor LED Relay RTC – This one gives you a lot, breadboards, resistors, displays, buzzers, motors and connecting cables.

Deluxe Modules for Arduino UNO R3 Starter Kit W/ LED Matrix/Motion Sensor/Breadboard/LCD/Blueooth/Motor/Servo/Keypad/Makerduino – similar to above with some more advanced parts

12th November 2015 0 comment