WiFi with ESP8266/ESP32 in Arduino

Introduction

WiFi lets your ESP8266 or ESP32 connect to the internet or local networks. This helps your device send or receive data wirelessly.

You want to control home devices from your phone using WiFi.

You want to send sensor data to a website or cloud service.

You want your device to download updates or information from the internet.

You want to create a small web server on your ESP to show data or control things.

You want to connect multiple ESP devices together over WiFi.

Syntax

Arduino

#include <WiFi.h>  // For ESP32
// or
#include <ESP8266WiFi.h>  // For ESP8266

const char* ssid = "yourNetworkName";
const char* password = "yourPassword";

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nConnected to WiFi");
}

void loop() {
  // Your code here
}

Use #include <WiFi.h> for ESP32 and #include <ESP8266WiFi.h> for ESP8266.

WiFi.begin(ssid, password) starts the connection to your WiFi network.

Examples

Connects ESP32 to a WiFi network named "HomeWiFi" with password "12345678".

Arduino

#include <WiFi.h>

const char* ssid = "HomeWiFi";
const char* password = "12345678";

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nConnected to HomeWiFi");
}

void loop() {}

Connects ESP8266 to a WiFi network named "CafeWiFi" with password "coffee123".

Arduino

#include <ESP8266WiFi.h>

const char* ssid = "CafeWiFi";
const char* password = "coffee123";

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("\nConnected to CafeWiFi");
}

void loop() {}

Sample Program

This program connects the ESP32 to a WiFi network called "TestNetwork" with password "testpass". It prints dots while connecting, then shows a success message and the device's IP address.

Arduino

#include <WiFi.h>

const char* ssid = "TestNetwork";
const char* password = "testpass";

void setup() {
  Serial.begin(115200);
  Serial.println("Connecting to WiFi...");
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("\nWiFi connected!");
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
}

void loop() {
  // Nothing here
}

Important Notes

Make sure your WiFi network name and password are correct.

The IP address shown is assigned by your router and may be different each time.

Use Serial.begin(115200) to see messages in the Serial Monitor at 115200 baud rate.

Summary

WiFi allows ESP8266/ESP32 to connect to wireless networks.

Use WiFi.begin(ssid, password) to start connection.

Check connection status with WiFi.status() and get IP with WiFi.localIP().

Practice

1. What is the main purpose of WiFi.begin(ssid, password) in ESP8266/ESP32 programming?

easy

A. To start connecting the device to a WiFi network

B. To disconnect from the current WiFi network

C. To check the current WiFi signal strength

D. To get the IP address of the device

Solution

1. Step 1: Understand the function purpose

   WiFi.begin(ssid, password) is used to initiate connection to a WiFi network using the given network name (SSID) and password.

2. Step 2: Compare with other options

   Disconnecting, checking signal strength, or getting IP address are done by other functions, not WiFi.begin.

3. Final Answer:

   To start connecting the device to a WiFi network -> Option A

4. Quick Check:

   WiFi.begin starts connection [OK]

Hint: Remember: begin means start connection [OK]

Common Mistakes:

• Confusing begin with disconnect
• Thinking it returns IP address
• Assuming it checks signal strength

2. Which of the following is the correct syntax to check if the ESP8266 is connected to WiFi?

easy

A. if (WiFi.connected())

B. if (WiFi.checkConnection())

C. if (WiFi.isConnected())

D. if (WiFi.status() == WL_CONNECTED)

Solution

1. Step 1: Recall the correct method to check WiFi connection

   The standard way is to use WiFi.status() and compare it to WL_CONNECTED to confirm connection.

2. Step 2: Verify other options

   Methods like WiFi.connected(), WiFi.isConnected(), or WiFi.checkConnection() do not exist in the ESP8266 WiFi library.

3. Final Answer:

   if (WiFi.status() == WL_CONNECTED) -> Option D

4. Quick Check:

   WiFi.status() == WL_CONNECTED checks connection [OK]

Hint: Use WiFi.status() with WL_CONNECTED constant [OK]

Common Mistakes:

• Using non-existent methods like WiFi.connected()
• Confusing status check syntax
• Forgetting to compare with WL_CONNECTED

3. What will the following code print if the ESP8266 successfully connects to WiFi?

WiFi.begin("MySSID", "MyPass");
while (WiFi.status() != WL_CONNECTED) {
  delay(500);
}
Serial.println(WiFi.localIP());

medium

A. The IP address assigned to the ESP8266

B. The SSID of the WiFi network

C. The WiFi password

D. Nothing, it will cause an error

Solution

1. Step 1: Analyze the connection loop

   The code waits until WiFi.status() returns WL_CONNECTED, meaning the device is connected to WiFi.

2. Step 2: Understand the output command

   WiFi.localIP() returns the IP address assigned to the device by the router, which is printed to Serial.

3. Final Answer:

   The IP address assigned to the ESP8266 -> Option A

4. Quick Check:

   WiFi.localIP() prints device IP [OK]

Hint: localIP() shows device IP after connection [OK]

Common Mistakes:

• Thinking it prints SSID or password
• Assuming it prints connection status
• Believing it causes an error

4. Identify the error in this ESP32 WiFi connection code:

WiFi.begin(ssid, password);
while (WiFi.status() = WL_CONNECTED) {
  delay(1000);
}
Serial.println("Connected!");

medium

A. Missing WiFi.begin() call

B. Incorrect delay value

C. Using single '=' instead of '==' in the while condition

D. No Serial.begin() before printing

Solution

1. Step 1: Check the while loop condition

   The condition uses a single '=' which is an assignment, not a comparison. It should be '==' to compare values.

2. Step 2: Confirm other parts

   WiFi.begin() is called, delay is valid, and Serial.begin() is not shown but not the main error here.

3. Final Answer:

   Using single '=' instead of '==' in the while condition -> Option C

4. Quick Check:

   Use '==' for comparison in conditions [OK]

Hint: Use '==' to compare, '=' assigns value [OK]

Common Mistakes:

• Confusing '=' with '==' in conditions
• Ignoring Serial.begin() setup
• Assuming delay value causes error

5. You want your ESP32 to connect to WiFi and print its IP address only after a successful connection, but also stop trying after 10 seconds if it fails. Which code snippet correctly implements this?

hard

A. WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
if (millis() > 10000) break;
}
Serial.println(WiFi.localIP());

B. WiFi.begin(ssid, password);
unsigned long start = millis();
while (WiFi.status() != WL_CONNECTED && millis() - start < 10000) {
delay(500);
}
if (WiFi.status() == WL_CONNECTED) {
Serial.println(WiFi.localIP());
} else {
Serial.println("Failed to connect");
}

C. WiFi.begin(ssid, password);
for (int i = 0; i < 20; i++) {
if (WiFi.status() == WL_CONNECTED) break;
delay(500);
}
Serial.println(WiFi.localIP());

D. WiFi.begin(ssid, password);
while (WiFi.status() == WL_CONNECTED) {
delay(10000);
}
Serial.println(WiFi.localIP());

Solution

1. Step 1: Understand the timeout logic

   WiFi.begin(ssid, password); unsigned long start = millis(); while (WiFi.status() != WL_CONNECTED && millis() - start < 10000) { delay(500); } if (WiFi.status() == WL_CONNECTED) { Serial.println(WiFi.localIP()); } else { Serial.println("Failed to connect"); } uses millis() to track elapsed time and stops trying after 10 seconds (10000 ms) if not connected.

2. Step 2: Check connection and print accordingly

   It prints the IP only if connected; otherwise, it prints a failure message. This matches the requirement exactly.

3. Final Answer:

   The code with 10-second timeout using millis() and conditional IP printing -> Option B

4. Quick Check:

   Use millis() for timeout and check status before printing [OK]

Hint: Use millis() to limit connection wait time [OK]

Common Mistakes:

• Not stopping connection attempts after timeout
• Printing IP without checking connection
• Using wrong while condition logic