Constants

These are expressions that are predefined in arduino language

• false - false is used to define zero.

• true -true is used to define a non-zero value in programming, mostly 1 but -1 or 200 could also be true

• HIGH - a pin is said to be High if:

  • a voltage present at the pin is greater than 3.3v (5V boards)
  • a voltage present at the pin is greater than 2.0v (3.3V boards)

• LOW -a pin is said to be low if:

  • a voltage less than 1.5v is there in the pin(5v)
  • a voltage less than 1.0v is present at the pin(3.3v)

• INPUT -When a pin is set to INPUT, it means that it will permit a relatively small amount of current to pass through it, per unit of the applied voltage at that point.

• OUTPUT- When a pin is configured as OUTPUT -it means that it would provide a significant amount of current to other circuits

Conversions

• (unsigned int) - modifies a value to unsigned int data type.

• (insigned long)- modifies a value to unsigned long data type.

• byte() - modifies a value to a byte data type.

• char() - modifies a value to a char data type.

• int() - modifies a value to an int data type

• float() - modifies a value to an float data type

Data Types

Array

The array is a list of variables that are accessed by an index number

Example

  int myInts[6];
  int myPins[] = {2, 4, 8, 3, 6};
  int mySensVals[6] = {2, 4, -8, 3, 2};
  char message[6] = "hello";

  //accessing an array
  mypins[0] //this is same as 2 in myPins[]  array

  //setting an array

  myInts[0]=1 //same as setting the first value of myInts[] array to be 1

bool

a bool holds either of two values, true or false.

Example

int LEDpin = 4;     // LED on pin 4
int switchPin = 10; // momentary switch on 10, other side connected to ground

bool running = false;

void setup() {
  pinMode(LEDpin, OUTPUT);
  pinMode(switchPin, INPUT);
  digitalWrite(switchPin, HIGH);  // turn on pullup resistor
}

void loop() {
  if (digitalRead(switchPin) == LOW) {
    // switch is pressed - pullup keeps pin high normally
    delay(100);                     // delay to debounce switch
    running = !running;             // toggle running variable
    digitalWrite(LEDpin, running);  // indicate via LED
  }
}

byte

Byte holds an unsigned 8-bit number, between 0 to 255.

Example

byte running = 254;

void setup() {

}

void loop() {
}

char

The data-type used to hold a character value. Characters can also be stored as numbers

Example

char myChar = 'A';
char myChar = 65; // both are equivalent

int

The data-type used to store numbers.

Example

int countUp = 1;            //creates a variable integer called 'countUp'

void setup() {
  Serial.begin(9600);       // use the serial port to print the number
}

void loop() {
  countUp++;                //Adds 1 to the countUp int on every loop
  Serial.println(countUp);  // prints out the current state of countUp
  delay(1000);
}

string

The data-type used to represent text strings

Example

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2
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char myString[] = "This is the first line"
" this is the second line"
" etcetera";

word

A word can store at least 16 bits of the unsigned numbers (from 0 to 65535) (from 0 to 65535).

Example

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word w = 10000;