Arduino Master Sheet | 20+ Pro Examples

Arduino Pro Sheet

20+ Essential Hardware & Logic Snippets

Basics

01. Standard Blink

The fundamental test to ensure your board is alive.

blink.ino

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

void loop() {
  digitalWrite(LED_BUILTIN, HIGH);
  delay(1000);
  digitalWrite(LED_BUILTIN, LOW);
  delay(1000);
}

Logic

02. Hardware Debouncing

Software-level filter for mechanical button noise.

debounce.ino

const int pin = 2;
unsigned long lastDebounce = 0;
int state = HIGH;

void loop() {
  int read = digitalRead(pin);
  if (read != lastDebounce) {
    lastDebounce = millis();
    if (read == LOW) { /* Action on press */ }
  }
}

Sensors

03. Sensor Mapping (ADC to PWM)

Translating 10-bit input (0-1023) to 8-bit output (0-255).

void loop() {
  int sensor = analogRead(A0);
  int output = map(sensor, 0, 1023, 0, 255);
  analogWrite(9, output);
}

Advanced

04. Multitasking (Millis)

Running code without blocking execution with delay().

unsigned long pTime = 0;
void loop() {
  if (millis() - pTime >= 1000) {
    pTime = millis();
    // Execute every second
  }
}

Sensors

05. Ultrasonic Distance

Precise distance measurement using pulse timing.

long getDistance(int t, int e) {
  digitalWrite(t, LOW); delayMicroseconds(2);
  digitalWrite(t, HIGH); delayMicroseconds(10);
  digitalWrite(t, LOW);
  return pulseIn(e, HIGH) * 0.034 / 2;
}

Memory

06. Persistent Memory

Saving settings after power-off using EEPROM.update (prevents wear).

#include <EEPROM.h>
void save(int addr, byte val) {
  EEPROM.update(addr, val); // Writes only if value changed
}

Hardware

07. External Interrupts

Capturing high-speed external events instantly.

void setup() {
  attachInterrupt(digitalPinToInterrupt(2), isr, FALLING);
}
void isr() { /* Keep it fast! */ }

Actuators

08. Servo Sweep

Controlling position using the Servo library.

#include <Servo.h>
Servo myservo;
void setup() { myservo.attach(9); }
void loop() { myservo.write(90); } // 0 to 180 degrees

Communication

09. I2C Scanner

Utility to find the hex address of connected sensors.

#include <Wire.h>
void setup() {
  Wire.begin(); Serial.begin(9600);
  for(byte i=8; i<127; i++) {
    Wire.beginTransmission(i);
    if(Wire.endTransmission()==0) Serial.println(i, HEX);
  }
}

Pro

10. Direct Port Access

Bypassing digitalWrite for 10x faster switching speed.

void setup() { DDRB |= B00100000; } // Set Pin 13 as Output
void loop() {
  PORTB |= B00100000;  // High
  PORTB &= ~B00100000; // Low
}

Reliability

11. Watchdog Reset

Auto-rebooting the board if code freezes.

#include <avr/wdt.h>
void setup() { wdt_enable(WDTO_2S); }
void loop() { wdt_reset(); // Must be called every < 2s }

Sensors

12. DHT11 / DHT22 Reading

Using the DHT library to fetch environmental data.

#include "DHT.h"
DHT dht(2, DHT22);
void loop() {
  float h = dht.readHumidity();
  float t = dht.readTemperature();
}

Logic

13. Switch-Case State Machine

The cleanest way to handle system states (Idle, Run, Alarm).

enum State {IDLE, RUN};
State curr = IDLE;
void loop() {
  switch(curr) {
    case IDLE: if(btn) curr = RUN; break;
    case RUN: execute(); break;
  }
}

Hardware

14. Custom PWM Frequency

Modifying timers to remove audible coil whine from motors.

void setup() {
  // Set Timer 1 for 31kHz PWM on pins 9, 10
  TCCR1B = (TCCR1B & 0b11111000) | 0x01;
}

DSP

15. Simple Data Smoothing

Average filter to remove noise from analog sensors.

float smooth = 0;
void loop() {
  int raw = analogRead(A0);
  smooth = (raw * 0.1) + (smooth * 0.9); // Low-pass filter
}

Actuators

16. Stepper Pulse Control

Driving a stepper motor using Step/Dir signals.

void step() {
  digitalWrite(stepPin, HIGH);
  delayMicroseconds(500);
  digitalWrite(stepPin, LOW);
  delayMicroseconds(500);
}

Debugging

17. Check Available RAM

Utility to prevent stack overflow on Nano/Uno boards.

int freeRam() {
  extern int __heap_start, *__brkval;
  int v;
  return (int)&v - (__brkval == 0 ? (int)&__heap_start : (int)__brkval);
}

Optimization

18. Saving RAM (F Macro)

Moving static strings to Flash memory to save precious RAM.

void setup() {
  Serial.println(F("This string is stored in FLASH!"));
}

Hardware

19. Internal 1.1V Reference

Better precision for low-voltage sensor measurements.

void setup() {
  analogReference(INTERNAL); // 1.1V on Uno/Nano
}

Serial

20. High Speed Serial

Standard setup for high-speed telemetry and ESP8266 talk.

void setup() {
  Serial.begin(115200);
  while(!Serial); // Wait for USB connection
}