WiFi with ESP8266/ESP32 in Arduino - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this ESP8266 WiFi connection code?

Consider this Arduino code for ESP8266 that tries to connect to a WiFi network. What will be printed on the Serial Monitor?

Arduino

void setup() {
  Serial.begin(115200);
  WiFi.begin("MySSID", "WrongPassword");
  int attempts = 0;
  while (WiFi.status() != WL_CONNECTED && attempts < 5) {
    delay(1000);
    Serial.print(".");
    attempts++;
  }
  if (WiFi.status() == WL_CONNECTED) {
    Serial.println("Connected!");
  } else {
    Serial.println("Failed to connect");
  }
}

void loop() {}

A .....Failed to connect

B .....Connected!

C Connected!

D Failed to connect

💡 Hint

Think about what happens if the password is wrong and how many times the code tries to connect.

The code tries to connect 5 times, printing a dot each second. Since the password is wrong, it never connects, so after 5 dots it prints 'Failed to connect'.

🧠 Conceptual

intermediate

Which WiFi mode allows ESP32 to connect to another WiFi network?

ESP32 supports multiple WiFi modes. Which mode should you use if you want your ESP32 to connect to your home WiFi router?

A WiFi.mode(WIFI_STA);

B WiFi.mode(WIFI_AP);

C WiFi.mode(WIFI_AP_STA);

D WiFi.mode(WIFI_OFF);

💡 Hint

Think about the mode where the device acts as a client connecting to an access point.

WIFI_STA mode sets the ESP32 as a station (client) that connects to an existing WiFi network (access point).

🔧 Debug

advanced

Why does this ESP32 code fail to connect to WiFi?

Look at this code snippet. It never prints 'Connected!'. What is the bug?

Arduino

void setup() {
  Serial.begin(115200);
  WiFi.begin("SSID", "password");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println("Connecting...");
  }
  Serial.println("Connected!");
}

void loop() {}

A The delay is too short to connect

B WiFi.begin() is missing WiFi.mode(WIFI_STA); before it

C Serial.begin() baud rate is incorrect

D WiFi.status() returns WL_DISCONNECTED instead of WL_CONNECTED

💡 Hint

ESP32 needs to be in the right mode before connecting.

Without setting WiFi.mode(WIFI_STA), the ESP32 may not connect properly because it defaults to AP mode or no mode.

📝 Syntax

advanced

Which option correctly initializes WiFi on ESP8266 to create an access point?

Choose the correct code snippet to start an access point named "MyESP" with password "12345678" on ESP8266.

A WiFi.createAP("MyESP", "12345678");

B WiFi.beginAP("MyESP", "12345678");

C WiFi.startAP("MyESP", "12345678");

D WiFi.softAP("MyESP", "12345678");

💡 Hint

Check the official ESP8266 WiFi library function names.

The correct function to start an access point on ESP8266 is WiFi.softAP().

🚀 Application

expert

How many IP addresses will be assigned after this ESP32 code runs?

Consider this ESP32 code that sets up both station and access point modes. How many IP addresses will the ESP32 have after setup?

Arduino

void setup() {
  WiFi.mode(WIFI_AP_STA);
  WiFi.softAP("ESP32_AP", "password");
  WiFi.begin("HomeSSID", "homepass");
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
  }
}

void loop() {}

A 1

B 3

C 2

D 0

💡 Hint

Think about IP addresses for both station and access point interfaces.

In WIFI_AP_STA mode, ESP32 acts as both access point and station, so it gets one IP for each interface, totaling 2 IP addresses.

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