Crash Course Programming for Arduino: Difference between revisions

Variables can be typecasted (= converted from one datatype to another) by using the relevant functions: int(), long() or float().

void 0 bytes, 0bit, 0

boolean 1 byte, 1 bit, 0/1

String

...

== Variables ==

e.g.  

int x;

byte b;

Variable names mustn't contain any special characters, especially no spaces. Try to use descriptive names for your variables. It's widely regarded good practise to use [http://en.wikipedia.org/wiki/Camel_case#Variations_and_synonyms lower camel case] for improved readability.

// This is nice lower camel case

boolean isEnabled;

Variables can be declared and instantiated in one step:

e.g.  

int x = 5;

long r = random(255);

int values[6] = {0,1,2,3,4,5};

===Variable Scope===

If a variable is declared ''inside'' a function, it is a ''local'' variable, if declared ''outside'' any function, it's scope is global, that means it can be accessed from anywhere.

// Global variable

int x = 7;

   int a = 8;

}

Never give local variables and global variables the same name. Two local variables can have the same name only when they are defined in different functions!

// This is not ok!

int x = 5;

   int a = 12;

}

=== Arrays ===

Declaring Arrays is pretty much like declaring variables only for arrays the name is followed by square brackets '[]' enclosing an optional length parameter.

type name[length];

You don't have to define a length parameter but if if you do, the Array wont hold more elements than specified.

For example:

// Create an array without assigning values

int myArray[];

// Create a String (in C this is an Array of chars)

int myWord[] = "hello";

==== Accessing Arrays ====

You can access variables stored in an Array by their index. Indices go from 0 to length-1. In an Array with 3 elements the first element has the index 0 and the last element has the index 2.

int someNumbers[] = {45, 5, 6};

int firstElement = someNumbers[0]; // = 45

int secondElement = someNumbers[1]; // = 5

int thirdElement = someNumbers[2]; // = 6

==== Creating an Array of Strings ====

Since Strings itself already are Arrays, creating an Array of Strings is basically creating two-dimensional Arrays. Since all this goes pretty deep into C programming it's best to just follow the example. Note the extra asterisk after the type.

char* myWords[] = {"One", "Two", "Three"};

== Main Functions ==

An Arduino program consists of two basic functions: start() and loop():

void start() {

   // init code that is executed ONCE only: at the start of the program (eg. when power is attached)

   // code that gets executed as long as the arduino is powered

}

e.g. the two main Arduino functions:

void setup() {

// Anweisungen, die einmal beim Start des Programms ausgeführt werden

doWhatever();

}

Instructions can be summarised as a function, e.g.:

void randomizeColor() {

// Instructions

return;

}

or

int multipliziere(int a, int b) {

// Multipliziere a und b und gebe diesen Wert zurück

return a * b;

}

e.g.:

int x = multipliziere(2,5); // x = 10;

delay(1000);

c = min(x,y);

... see the Arduino Reference to find more pre-defined functions, that are ready to be used!