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Arduino Cheatsheet

A quick reference guide for Arduino development, covering essential concepts, code snippets, and hardware information for both beginners and advanced users.

Arduino Fundamentals

Basic Structure

Every Arduino program (sketch) has two essential functions:

void setup() {} - Runs once at the beginning of the program. Used for initialization.

void loop() {} - Runs repeatedly after setup() finishes. This is where the main program logic goes.

Example:

void setup() {
  // Initialize serial communication
  Serial.begin(9600);
}

void loop() {
  // Print "Hello, world!" to the serial monitor
  Serial.println("Hello, world!");
  delay(1000); // Wait for 1 second
}

Data Types

int

Integer (whole number). Typically 2 bytes (-32,768 to 32,767).

byte

Unsigned integer (0 to 255).

long

Long integer. Typically 4 bytes (-2,147,483,648 to 2,147,483,647).

float

Floating-point number (number with decimal point). 4 bytes.

boolean

Boolean value (true or false).

char

Character. 1 byte.

Digital I/O

pinMode(pin, mode)

Sets the specified pin as INPUT, OUTPUT, or INPUT_PULLUP.

digitalWrite(pin, value)

Writes HIGH or LOW to a digital pin (only if the pin is set as OUTPUT).

digitalRead(pin)

Reads the value (HIGH or LOW) from a digital pin.

Analog I/O & Serial Communication

Analog I/O

analogRead(pin)

Reads the value from the specified analog pin (0 to 1023).

analogWrite(pin, value)

Writes an analog value (PWM signal) to a pin (0 to 255). Only works on PWM enabled pins (marked with ~ on the board).

analogReference(type)

Configures the reference voltage used for analog input (DEFAULT, INTERNAL, EXTERNAL).

Serial Communication

Serial.begin(baudRate)

Initializes serial communication at the specified baud rate (e.g., 9600, 115200).

Serial.print(data)

Sends data to the serial port as human-readable ASCII text.

Serial.println(data)

Sends data to the serial port, followed by a carriage return and line feed.

Serial.available()

Gets the number of bytes (characters) available for reading from the serial port.

Serial.read()

Reads the first available byte of incoming serial data.

Time Functions

delay(milliseconds)

Pauses the program for the amount of time (in milliseconds) specified as parameter.

millis()

Returns the number of milliseconds since the Arduino board began running the current program. This number will overflow (go back to zero) after approximately 50 days.

micros()

Returns the number of microseconds since the Arduino board began running the current program. This number will overflow (go back to zero) after approximately 70 minutes.

Control Structures & Operators

Control Structures

if (condition) { ... } - Executes code block if the condition is true.

if (condition) { ... } else { ... } - Executes one code block if the condition is true and another if the condition is false.

for (initialization; condition; increment) { ... } - Repeats a block of code a specific number of times.

while (condition) { ... } - Repeats a block of code as long as the condition is true.

do { ... } while (condition); - Executes a block of code once, and then repeats as long as the condition is true.

switch (expression) { case value1: ... break; case value2: ... break; default: ... } - Selects one of several code blocks to execute based on the value of an expression.

Operators

=

Assignment operator (assigns a value to a variable).

==

Equality operator (checks if two values are equal).

!=

Inequality operator (checks if two values are not equal).

>

Greater than operator.

<

Less than operator.

&&

Logical AND operator (returns true if both conditions are true).

||

Logical OR operator (returns true if at least one condition is true).

!

Logical NOT operator (reverses the logical state of its operand).

Math Operators

+

Addition.

-

Subtraction.

*

Multiplication.

/

Division.

%

Modulo (returns the remainder of a division).

Advanced Arduino

Interrupts

attachInterrupt(digitalPinToInterrupt(pin), ISR, mode)

Attaches an interrupt to the specified pin. ISR is the interrupt service routine, and mode can be LOW, CHANGE, RISING, or FALLING.

detachInterrupt(digitalPinToInterrupt(pin))

Detaches the interrupt on the specified pin.

interrupts()

Re-enables interrupts (after they have been disabled by noInterrupts()).

noInterrupts()

Disables interrupts.

Libraries

Libraries provide extra functionality to your sketches. To include a library:

#include <LibraryName.h>

Examples:

  • #include <Wire.h> - For I2C communication
  • #include <SPI.h> - For SPI communication
  • #include <Servo.h> - For controlling servo motors
  • #include <LiquidCrystal.h> - For LCD display

EEPROM

EEPROM.write(address, value)

Writes a byte to the EEPROM at the specified address.

EEPROM.read(address)

Reads a byte from the EEPROM at the specified address.

EEPROM.update(address, value)

Writes a byte to the EEPROM at the specified address, only if the new value is different from the old value.
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