1. Setting up a basic program with Arduino
Variable Declarations
Program Setup
References:
Exploring Arduino – by Jeremy Blum
Arduino Project Book – by Arduino

2. Single line comments denoted by //
Understanding Code Basics
Comments:
Single line
Single line comments denoted by //
Compiler ignores everything after the symbol
Comment out a line to troubleshoot
sval = sval / 5;    // average   sval = sval / 4;    // scale to 8 bits ( )   sval = 255 - sval;  // invert output
Multiple line
Multiple line comments start with /* and end with*/
Compiler ignores everything between the symbols
Used for large descriptions and program details
/* Blink Turns on an LED on for one second, then off for one second, repeatedly. This example code is in the public domain. (Another valid comment) */

3. Variable Declarations:
Understanding Code Basics
Variable Declarations:
Variables are a place in the Arduinos memory that
holds information
int –Primary for number storage
void loop() {   int i = 2;   int j = 3;   int k;   k = myMultiplyFunction(i, j); // k now contains 6   Serial.println(k);
char – Stores a character value: ex ‘A’ . Characters can be
stored as numbers.
Example Code
char myChar = 'A’;
char myChar = 65; // both are equivalent

4. Variable Declarations:
Understanding Code Basics
Variable Declarations:
byte –Stores an unassigned 8-bit number from 0-255
byte x;
x = 0;
x = x - 1; // x now contains rolls over in neg. direction
x = 255; x = x + 1; // x now contains 0 - rolls over
long –Extended size variables for number storage, store
32 bits (4 bytes) from -2,147,483,648 to 2,147,483,647
Example Code
long speedOfLight = L; // see the Integer Constants page for explanation of the 'L'

5. Variable Declarations:
Understanding Code Basics
Variable Declarations:
float –Used for numbers that have decimal numbers
Example Code
float myfloat;
float sensorCalbrate = 1.117;
int x;
int y;
float z;
x = 1;
y = x / 2; // y now contains 0, ints can't hold fractions
z = (float)x / 2.0; // z now contains .5 (you have to use 2.0, not 2)

6. Variable Declarations:
Understanding Code Basics
Variable Declarations:
Double –Double precision floating point number. On the Uno and other ATMEGA based boards, this occupies 4 bytes. That is, the double implementation is exactly the same as the float, with no gain in precision.
On the Arduino Due, doubles have 8-byte (64 bit) precision.
If you borrow code from other sources that includes double variables may wish to examine the code to see if the implied precision is different from that actually achieved on ATMEGA based Arduinos.

7. Variable Declarations:
Understanding Code Basics
Variable Declarations:
string – In general, used to represent text
char Str1[15]; char Str2[8] = {'a', 'r', 'd', 'u', 'i', 'n', 'o'}; char Str3[8] = {'a', 'r', 'd', 'u', 'i', 'n', 'o', '\0'}; char Str4[ ] = "arduino"; char Str5[8] = "arduino"; char Str6[15] = "arduino";
Possibilities for declaring strings
Declare an array of chars without initializing it as in Str1
Declare an array of chars (with one extra char) and the compiler will add the required null character, as in Str2
Explicitly add the null character, Str3
Initialize with a string constant in quotation marks; the compiler will size the array to fit the string constant and a terminating null character, Str4
Initialize the array with an explicit size and string constant, Str5
Initialize the array, leaving extra space for a larger string, Str6

8. void setup – Used at the beginning of the program. It is where
Understanding Code Basics
Program Setup:
void setup – Used at the beginning of the program. It is where
variables are initialized, pins are defined as inputs or outputs.
Executes what is between the { } (curly braces)
Only runs once. When the Arduino is started or reset.
void setup() {   // initialize digital pin LED_BUILTIN as an output.   pinMode(LED_BUILTIN, OUTPUT); } // the loop function runs over and over again forever void loop() {   digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)   delay(1000);                       // wait for a second   digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW   delay(1000);                       // wait for a second }

9. void loop – Runs continuously after the setup. This is where
Understanding Code Basics
Program Setup:
void loop – Runs continuously after the setup. This is where
inputs and outputs are turned on, motors controlled, sensors are
Read.
Executes what is between the { } (curly braces)
void setup() {   // initialize digital pin LED_BUILTIN as an output.   pinMode(LED_BUILTIN, OUTPUT); } // the loop function runs over and over again forever void loop() {   digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)   delay(1000);                       // wait for a second   digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW   delay(1000);                       // wait for a second }

10. pinMode– Configures a specific pin number to be an input or an output.
Understanding Code Basics
Program Setup:
pinMode– Configures a specific pin number to be an input or
an output.
void setup() {
pinMode(13, OUTPUT); // sets the digital pin 13 as output }
void loop()
{ digitalWrite(13, HIGH); // sets the digital pin 13 on
delay(1000); // waits for a second
digitalWrite(13, LOW); // sets the digital pin 13 off }

11. digitalRead– Reads the value from a specified pin
Understanding Code Basics
Program Setup:
digitalRead– Reads the value from a specified pin
int ledPin = 13; // LED connected to digital pin 13
int inPin = 7; // pushbutton connected to digital pin 7
int val = 0; // variable to store the read value
void setup() {
pinMode(ledPin, OUTPUT); // sets the digital pin 13 as output pinMode(inPin, INPUT); // sets the digital pin 7 as input }
void loop()
val = digitalRead(inPin); // read the input pin digitalWrite(ledPin, val); // sets the LED to the button's value

12. digitalWrite– Writes a HIGH or Low value to a specific pin
Understanding Code Basics
Program Setup:
digitalWrite– Writes a HIGH or Low value to a specific pin
void setup() {
pinMode(13, OUTPUT); // sets the digital pin 13 as output }
void loop()
{ digitalWrite(13, HIGH); // sets the digital pin 13 on
delay(1000); // waits for a second
digitalWrite(13, LOW); // sets the digital pin 13 off }

13. delay– A delay (wait) time in milliseconds. The Arduino does
Understanding Code Basics
Program Setup:
delay– A delay (wait) time in milliseconds. The Arduino does
Nothing during this specified amount of time.
void setup() {
pinMode(13, OUTPUT); // sets the digital pin 13 as output }
void loop()
{ digitalWrite(13, HIGH); // sets the digital pin 13 on
delay(1000); // waits for a second
digitalWrite(13, LOW); // sets the digital pin 13 off }

14. if– checks for a condition and executes the proceeding statement
Understanding Code Basics
Program Setup:
if– checks for a condition and executes the proceeding statement
if the condition was found to be true.
else– follows the “if” and is for when the “if” condition is found to be false.
if (condition1) {
// do Thing A }
else if (condition2)
// do Thing B
else {
// do Thing C
if (temperature >= 70) {
//Danger! Shut down the system }
else if (temperature >= 60 && temperature < 70)
//Warning! User attention required
} else
//Safe! Continue usual tasks... }