IoT Engineering Course using ESP32 Wifi Robots

📘Real-Time Control (Detailed Explanation)

🎯 Lesson Objective

In this lesson, students will learn:

How complete system integration works
How ESP32 reads commands from Blynk
How functions control robot movement
How real-time control is achieved

By the end of this lesson, students will understand both working AND internal logic of the system.

🤖 What We Are Doing in This Lesson

We are combining:

Motor control logic
WiFi connectivity
Blynk communication

👉 Into one complete working system

🔄 Complete System Flow

Button Press → Blynk Cloud → ESP32 → Function Call → Motor Movement

💻 Complete Code (Reference)

#define BLYNK_TEMPLATE_ID “YourTemplateID”
#define BLYNK_TEMPLATE_NAME “WiFi Robot”
#define BLYNK_AUTH_TOKEN “YourAuthToken”

#include <WiFi.h>
#include <BlynkSimpleEsp32.h>

char ssid[] = “YourWiFiName”;
char pass[] = “YourPassword”;

// Motor Pins
int IN1 = 26;
int IN2 = 27;
int IN3 = 14;
int IN4 = 12;

🔍 SECTION 1: Movement Functions (CORE LOGIC)

These functions control the actual movement of the robot.

🔹 1. stopRobot()

void stopRobot() {
digitalWrite(IN1, LOW);
digitalWrite(IN2, LOW);
digitalWrite(IN3, LOW);
digitalWrite(IN4, LOW);
}

👉 Explanation:

All pins LOW → No current → Motors stop
This is a safety function

🔹 2. forward()

void forward() {
digitalWrite(IN1, HIGH);
digitalWrite(IN2, LOW);
digitalWrite(IN3, HIGH);
digitalWrite(IN4, LOW);
}

👉 Explanation:

Motor A → Forward
Motor B → Forward
Robot moves straight

🔹 3. backward()

void backward() {
digitalWrite(IN1, LOW);
digitalWrite(IN2, HIGH);
digitalWrite(IN3, LOW);
digitalWrite(IN4, HIGH);
}

👉 Explanation:

Both motors reverse direction
Robot moves backward

🔹 4. left()

void left() {
digitalWrite(IN1, LOW);
digitalWrite(IN2, HIGH);
digitalWrite(IN3, HIGH);
digitalWrite(IN4, LOW);
}

👉 Explanation:

Left motor → backward
Right motor → forward
Robot turns left

🔹 5. right()

void right() {
digitalWrite(IN1, HIGH);
digitalWrite(IN2, LOW);
digitalWrite(IN3, LOW);
digitalWrite(IN4, HIGH);
}

👉 Explanation:

Left motor → forward
Right motor → backward
Robot turns right

🔍 SECTION 2: BLYNK_WRITE() (MOST IMPORTANT PART)

This is where ESP32 receives data from mobile app

🧠 How Button Works Internally

In Blynk:

Button ON → sends 1
Button OFF → sends 0

👉 This value is received in ESP32

🔹 Forward Button (V0)

BLYNK_WRITE(V0) {
int value = param.asInt();

if (value == 1) {
forward();
} else {
stopRobot();
}
}

🔍 Explanation:

BLYNK_WRITE(V0) → triggers when V0 button changes
param.asInt() → reads value from app

Case 1:

Button pressed → value = 1
Calls → forward()

Case 2:

Button released → value = 0
Calls → stopRobot()

🔹 Backward Button (V1)

BLYNK_WRITE(V1) {
int value = param.asInt();

if (value == 1) {
backward();
} else {
stopRobot();
}
}

🔹 Left Button (V2)

BLYNK_WRITE(V2) {
int value = param.asInt();

if (value == 1) {
left();
} else {
stopRobot();
}
}

🔹 Right Button (V3)

BLYNK_WRITE(V3) {
int value = param.asInt();

if (value == 1) {
right();
} else {
stopRobot();
}
}

🧠 IMPORTANT CONCEPT: EVENT-BASED PROGRAMMING

👉 Unlike loop-based control:

Code runs only when button is pressed
This is called event-driven system

🔍 SECTION 3: setup() FUNCTION

void setup() {
Serial.begin(9600);

pinMode(IN1, OUTPUT);
pinMode(IN2, OUTPUT);
pinMode(IN3, OUTPUT);
pinMode(IN4, OUTPUT);

stopRobot();

Blynk.begin(BLYNK_AUTH_TOKEN, ssid, pass);
}

🔍 Explanation:

Serial.begin() → debugging
pinMode() → set pins as output
stopRobot() → safety start
Blynk.begin() → connects ESP32 to:
- WiFi
- Blynk cloud

🔍 SECTION 4: loop() FUNCTION

void loop() {
Blynk.run();
}

🔍 Explanation:

Keeps connection alive
Listens for incoming commands
Without this → nothing works

🧪 REAL-TIME FLOW (VERY IMPORTANT)

User presses button in app
App sends value (1) to Blynk Cloud
ESP32 receives it
Corresponding BLYNK_WRITE() runs
Function is called
Motors move

⚠️ IMPORTANT BEHAVIOR

👉 If two buttons are pressed together:

Commands may conflict
Robot may behave unexpectedly

👉 Solution:

Use only one button at a time

🧠 Key Learning Concepts

Event-driven programming
Function-based design
Real-time communication
Input → Processing → Output system

📝 Lesson Summary

In this lesson, students deeply understood how a WiFi-controlled robot works internally. They learned how mobile app commands are received, processed, and converted into physical movement using structured programming.

📌 Practice Task

Add Serial print inside each function
Display which button is pressed
Try pressing multiple buttons and observe behavior