How to Use Pointers in Arduino: Simple Guide with Examples

In Arduino, you use pointers to store memory addresses of variables, allowing indirect access and modification of data. Declare a pointer with the * symbol, assign it the address of a variable using &, and access the value via *pointer.

Syntax

To use pointers in Arduino, declare a pointer variable with the type it points to, followed by *. Assign it the address of a variable using &. Access or modify the value at that address using * (dereference operator).

• Type *pointerName; - declares a pointer to a variable of Type.
• pointerName = &variable; - assigns the pointer the address of variable.
• *pointerName - accesses the value stored at the pointer's address.

arduino

int value = 10;
int *ptr = &value;

// Access value via pointer
int x = *ptr;

// Change value via pointer
*ptr = 20;

Example

This example shows how to declare a pointer to an integer, print the original value, change it using the pointer, and print the updated value.

arduino

#include <Arduino.h>

int value = 5;
int *ptr = &value;

void setup() {
  Serial.begin(9600);
  delay(1000); // Wait for Serial

  Serial.print("Original value: ");
  Serial.println(value);

  *ptr = 15; // Change value using pointer

  Serial.print("Updated value via pointer: ");
  Serial.println(value);
}

void loop() {
  // Nothing here
}

Output

Original value: 5
Updated value via pointer: 15

Common Pitfalls

Common mistakes when using pointers in Arduino include:

• Not initializing pointers before use, which can cause crashes.
• Dereferencing null or uninitialized pointers.
• Confusing the address-of operator & with the dereference operator *.
• Modifying data through pointers without understanding the original variable's scope.

Always initialize pointers and ensure they point to valid memory before dereferencing.

arduino

int *ptr; // Uninitialized pointer

void setup() {
  Serial.begin(9600);
  // Serial.println(*ptr); // WRONG: ptr not initialized, causes error

  static int value = 10;
  ptr = &value; // Correct initialization
  Serial.println(*ptr); // Prints 10
}

Output

10

Quick Reference

Concept	Syntax	Description
Declare pointer	Type *ptr;	Creates a pointer to a variable of Type
Assign address	ptr = &var;	Pointer stores address of var
Dereference	*ptr	Access or modify value at pointer address
Null pointer	ptr = nullptr;	Pointer points to nothing (safe initialization)
Pointer to const	const Type *ptr;	Pointer to read-only data

Key Takeaways

Pointers store memory addresses and allow indirect access to variables in Arduino.

Always initialize pointers before using them to avoid errors or crashes.

Use the & operator to get a variable's address and * to access or change its value.

Be careful not to dereference null or uninitialized pointers.

Pointers can help manage memory efficiently but require careful handling.