Common Interview Questions on Arduino & ESP32-IoT, Bluetooth, Sensors, Power Management, FreeRTOS

Common Interview Questions on Arduino & ESP32

ESP32 is a powerful microcontroller from Espressif, widely used in IoT, automation, robotics, and embedded systems. Here are the most commonly asked Arduino ESP32 interview questions, categorized for better understanding.

1. Basics of ESP32 & Arduino

Q1: What is ESP32?

A:
ESP32 is a low-cost, low-power, dual-core microcontroller with built-in Wi-Fi & Bluetooth capabilities. It is widely used in IoT, home automation, and industrial applications.

Common Interview Questions on Arduino & ESP32-IoT, Bluetooth, Sensors, Power Management, FreeRTOS

Q2: What are the key features of ESP32?

Dual-core Xtensa 32-bit LX6 CPU
Built-in Wi-Fi (802.11 b/g/n) and Bluetooth (BLE 4.2/5.0)
Operating voltage: 3.3V
Multiple GPIOs with PWM, ADC, DAC, I2C, SPI, UART
Deep sleep mode for ultra-low power consumption

2. ESP32 vs Other Microcontrollers

Q3: How is ESP32 different from ESP8266?

Feature	ESP8266	ESP32
CPU	Single-core	Dual-core
Clock Speed	80 MHz	240 MHz
Wi-Fi	Yes	Yes
Bluetooth	No	Yes (BLE & Classic)
GPIO Pins	~11	36
ADC	10-bit	12-bit
Power Consumption	Higher	Lower (Deep Sleep Mode)

Q4: How does ESP32 compare with Arduino Uno?

Feature	Arduino Uno	ESP32
CPU	8-bit AVR	32-bit Xtensa
Clock Speed	16 MHz	240 MHz
Wi-Fi	No	Yes
Bluetooth	No	Yes
GPIO Pins	14	36
ADC	10-bit	12-bit
Power Consumption	Higher	Lower

3. Programming ESP32 with Arduino IDE

Q5: How do you program ESP32 using Arduino IDE?

Install ESP32 Board Manager in Arduino IDE.
Select "ESP32 Dev Module" under Tools → Board.
Connect ESP32 via USB and select the correct COM Port.
Write and upload the code.

Q6: How do you blink an LED on ESP32 using Arduino IDE?

#define LED_PIN 2  // Built-in LED pin on ESP32

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

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

4. Wi-Fi & IoT with ESP32

Q7: How do you connect ESP32 to Wi-Fi?

#include <WiFi.h>

const char* ssid = "YourSSID";
const char* password = "YourPassword";

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);
  
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting...");
  }
  Serial.println("WiFi Connected!");
}

void loop() {
}

Q8: How do you create a web server on ESP32?

#include <WiFi.h>
#include <WebServer.h>

const char* ssid = "YourSSID";
const char* password = "YourPassword";

WebServer server(80);

void handleRoot() {
  server.send(200, "text/html", "<h1>Hello from ESP32!</h1>");
}

void setup() {
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) delay(1000);
  
  server.on("/", handleRoot);
  server.begin();
}

void loop() {
  server.handleClient();
}

5. Bluetooth & ESP32

Q9: How do you use ESP32 as a Bluetooth server?

#include "BluetoothSerial.h"

BluetoothSerial SerialBT;

void setup() {
  Serial.begin(115200);
  SerialBT.begin("ESP32_BT");
}

void loop() {
  if (SerialBT.available()) {
    char c = SerialBT.read();
    Serial.write(c);
  }
}

6. Sensors & Communication Protocols

Q10: How do you interface ESP32 with a DHT11 temperature sensor?

#include <DHT.h>

#define DHTPIN 4
#define DHTTYPE DHT11

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(115200);
  dht.begin();
}

void loop() {
  float temp = dht.readTemperature();
  Serial.print("Temperature: ");
  Serial.println(temp);
  delay(2000);
}

Q11: What communication protocols does ESP32 support?

UART – Used for serial communication.
SPI – Used for high-speed data transfer.
I2C – Used for interfacing sensors like OLED, MPU6050.
CAN – Used in automotive applications.

7. Power Management & Deep Sleep

Q12: How do you put ESP32 into deep sleep mode?

void setup() {
  esp_sleep_enable_timer_wakeup(5000000); // Sleep for 5 seconds
  esp_deep_sleep_start();
}

void loop() {
}

Deep sleep mode significantly reduces power consumption.
ESP32 wakes up based on a timer, GPIO trigger, or sensor input.

8. Debugging & Troubleshooting ESP32

Q13: What are common issues faced with ESP32?

ESP32 not detected – Check drivers, use a different USB cable.
Upload error (Failed to connect to ESP32: Timed out) – Press BOOT while uploading.
Wi-Fi connection issues – Check SSID & password, move closer to the router.
ESP32 resets randomly – Check for power fluctuations, use a capacitor (100µF) across 3.3V and GND.

9. Real-Time Operating System (RTOS) in ESP32

Q14: Does ESP32 support FreeRTOS?

A: Yes, ESP32 comes with FreeRTOS pre-installed, allowing tasks to run in parallel.

Q15: How do you create a FreeRTOS task on ESP32?

void Task1(void *pvParameters) {
  while (1) {
    Serial.println("Task 1 Running");
    vTaskDelay(1000 / portTICK_PERIOD_MS);
  }
}

void setup() {
  Serial.begin(115200);
  xTaskCreate(Task1, "Task1", 1000, NULL, 1, NULL);
}

void loop() {
}

FreeRTOS allows multitasking, making ESP32 ideal for real-time IoT applications.

Common Interview Questions on Arduino & ESP32-IoT, Bluetooth, Sensors, Power Management, FreeRTOS