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// Called once at startup
void setup() {
  // Initialize pins, serial, etc.
  pinMode(13, OUTPUT);
  Serial.begin(9600);
}

// Called repeatedly
void loop() {
  // Main program logic
  digitalWrite(13, HIGH);
  delay(1000);
  digitalWrite(13, LOW);
  delay(1000);
}

// Set pin mode
pinMode(pin, INPUT);         // High impedance input
pinMode(pin, OUTPUT);        // Output
pinMode(pin, INPUT_PULLUP);  // Input with internal pull-up

// Write digital output
digitalWrite(pin, HIGH);     // Set pin high (5V/3.3V)
digitalWrite(pin, LOW);      // Set pin low (0V)

// Read digital input
int value = digitalRead(pin);  // Returns HIGH or LOW

const int buttonPin = 2;
const int ledPin = 13;

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  if (digitalRead(buttonPin) == LOW) {
    digitalWrite(ledPin, HIGH);
  } else {
    digitalWrite(ledPin, LOW);
  }
}

// Read analog input (0-1023 for 10-bit ADC)
int value = analogRead(A0);

// Convert to voltage (for 5V reference)
float voltage = value * (5.0 / 1023.0);

// PWM output (0-255)
analogWrite(pin, 127);  // 50% duty cycle

// Change PWM frequency (advanced)
// TCCR0B = TCCR0B & 0b11111000 | 0x01;

const int potPin = A0;
const int ledPin = 9;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  int potValue = analogRead(potPin);
  int brightness = map(potValue, 0, 1023, 0, 255);
  analogWrite(ledPin, brightness);
  delay(10);
}

void setup() {
  Serial.begin(9600);  // Start serial at 9600 baud
}

void loop() {
  // Print data
  Serial.print("Value: ");
  Serial.println(42);        // With newline
  Serial.printf("x=%d\n", x); // Formatted (ESP32)
  
  // Read data
  if (Serial.available() > 0) {
    char c = Serial.read();           // Read one byte
    String s = Serial.readString();   // Read string
    int n = Serial.parseInt();        // Read integer
  }
}

delay(1000);              // Wait 1000 milliseconds
delayMicroseconds(100);   // Wait 100 microseconds

unsigned long ms = millis();   // Milliseconds since start
unsigned long us = micros();   // Microseconds since start

// Non-blocking delay pattern
unsigned long previousMillis = 0;
const long interval = 1000;

void loop() {
  unsigned long currentMillis = millis();
  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;
    // Do something every interval
  }
}

#include <Servo.h>

Servo myServo;

void setup() {
  myServo.attach(9);  // Attach to pin 9
}

void loop() {
  myServo.write(90);   // Move to 90 degrees
  delay(1000);
  myServo.write(0);    // Move to 0 degrees
  delay(1000);
}

#include <Wire.h>

void setup() {
  Wire.begin();  // Join as master
}

void loop() {
  // Write to device
  Wire.beginTransmission(0x50);  // Address
  Wire.write(0x00);              // Register
  Wire.write(0xFF);              // Data
  Wire.endTransmission();
  
  // Read from device
  Wire.requestFrom(0x50, 1);     // Request 1 byte
  if (Wire.available()) {
    byte data = Wire.read();
  }
}

#include <SPI.h>

const int CS = 10;

void setup() {
  SPI.begin();
  pinMode(CS, OUTPUT);
  digitalWrite(CS, HIGH);
}

void loop() {
  digitalWrite(CS, LOW);         // Select device
  SPI.transfer(0x01);            // Send byte
  byte result = SPI.transfer(0); // Receive byte
  digitalWrite(CS, HIGH);        // Deselect
}

volatile int counter = 0;  // Use volatile!

void setup() {
  pinMode(2, INPUT_PULLUP);
  attachInterrupt(
    digitalPinToInterrupt(2),
    handleInterrupt,
    FALLING  // RISING, FALLING, CHANGE, LOW
  );
}

void handleInterrupt() {
  counter++;  // Keep ISR short!
}

void loop() {
  noInterrupts();  // Disable interrupts
  int c = counter;
  interrupts();    // Re-enable
  Serial.println(c);
}