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ESP32 - Control Car via Web
This guide shows you how to use the ESP32 to wirelessly control a robot car from a Web browser on your smartphone or PC using WiFi. The control is facilitated through a graphical web user interface using something called WebSocket, allowing for smooth and dynamic control of the car.
Hardware Used In This Tutorial
Or you can buy the following sensor kits:
| 1 | × | DIYables Sensor Kit (30 sensors/displays) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
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Introduction to 2WD RC Car and WebSocket
Now, why go for WebSocket? Here's the scoop:
- Without WebSocket, changing the car's direction would require reloading the page every time. Not ideal!
- However, with WebSocket, we establish a special connection between the webpage and the ESP32. This enables sending commands to the ESP32 in the background, without needing to reload the page. The result? The robot car moves seamlessly and in real-time. Pretty cool, right?
In a nutshell, the WebSocket connection enables the smooth, real-time control of the robot.
We have specific tutorials about 2WD RC Car and WebSocket. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:
- ESP32 - 2WD RC Car tutorial
- ESP32 - WebSocket tutorial
How It Works
The ESP32 code creates both a web server and a WebSocket Server. Here's how it works:
- When you enter the ESP32's IP address in a web browser, it requests the webpage (User Interface) from the ESP32.
- The ESP32's web server responds by sending the webpage's content (HTML, CSS, JavaScript).
- Your web browser then displays the webpage.
- The JavaScript code within the webpage establishes a WebSocket connection to the WebSocket server on the ESP32.
- Once this WebSocket connection is established, if you press/release the buttons on the webpage, the JavaScript code quietly sends the commands to the ESP32 through this WebSocket connection in the background.
- The WebSocket server on the ESP32, upon receiving the commands, controls the robot car accordingly.
The below table show commands list that the webpage sends to ESP32 based on the user's actions:
| User's Action | Button | Command | Car Action |
|---|---|---|---|
| PRESS | UP | 1 | MOVE FORWARD |
| PRESS | DOWN | 2 | MOVE BACKWARD |
| PRESS | LEFT | 4 | TURN LEFT |
| PRESS | RIGHT | 8 | TURN RIGHT |
| PRESS | STOP | 0 | STOP |
| RELEASE | UP | 0 | STOP |
| RELEASE | DOWN | 0 | STOP |
| RELEASE | LEFT | 0 | STOP |
| RELEASE | RIGHT | 0 | STOP |
| RELEASE | STOP | 0 | STOP |
Wiring Diagram between 2WD RC Car and ESP32
This image is created using Fritzing. Click to enlarge image
Typically, you need two power sources:
- One for the motor via the L298N module.
- Another for the ESP32 board, L298N module (Motor driver).
But, you can simplify it using just one power source for everything – four 1.5V batteries (totaling 6V). Here's how:
- Connect the batteries to the L298N module as shown.
- Remove two jumpers from ENA and ENB pins to 5 volts on the L298N module.
- Add a jumper labeled 5VEN (yellow circle on the diagram).
- Connect the 12V pin on the L298N module to the Vin pin on the ESP32 to power it directly from batteries.
Since the 2WD RC car has an on/off switch, you can optionally connect the battery via the switch to enable turning on/off power for the car. If you want to make it simple, just ignore the switch.
If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.
ESP32 Code
The webpage's content (HTML, CSS, JavaScript) are stored separately on an index.h file. So, we will have two code files on Arduino IDE:
- An .ino file that is ESP32 code, which creates a web sever and WebSocket Server, and controls car
- An .h file, which contains the webpage's content.
Quick Instructions
- If this is the first time you use ESP32, see how to setup environment for ESP32 on Arduino IDE.
- Do the wiring as above image.
- Connect the ESP32 board to your PC via a micro USB cable
- Open Arduino IDE on your PC.
- Select the right ESP32 board (e.g. ESP32 Dev Module) and COM port.
- Open the Library Manager by clicking on the Library Manager icon on the left navigation bar of Arduino IDE.
- Search “ESPAsyncWebServer”, then find the ESPAsyncWebServer created by lacamera.
- Click Install button to install ESPAsyncWebServer library.
- You will be asked to install the dependency. Click Install All button.
- Search “WebSockets”, then find the WebSockets created by Markus Sattler.
- Click Install button to install WebSockets library.
- On Arduino IDE, create new sketch, Give it a name, for example, esp32io.com.ino
- Copy the below code and open with Arduino IDE
/*
* This ESP32 code is created by esp32io.com
*
* This ESP32 code is released in the public domain
*
* For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-controls-car-via-web
*/
#include <WiFi.h>
#include <ESPAsyncWebServer.h>
#include <WebSocketsServer.h>
#include "index.h"
#define CMD_STOP 0
#define CMD_FORWARD 1
#define CMD_BACKWARD 2
#define CMD_LEFT 4
#define CMD_RIGHT 8
#define ENA_PIN 14 // The ESP32 pin GPIO14 connected to the ENA pin L298N
#define IN1_PIN 27 // The ESP32 pin GPIO27 connected to the IN1 pin L298N
#define IN2_PIN 26 // The ESP32 pin GPIO26 connected to the IN2 pin L298N
#define IN3_PIN 25 // The ESP32 pin GPIO25 connected to the IN3 pin L298N
#define IN4_PIN 33 // The ESP32 pin GPIO33 connected to the IN4 pin L298N
#define ENB_PIN 32 // The ESP32 pin GPIO32 connected to the ENB pin L298N
const char* ssid = "YOUR_WIFI_SSID"; // CHANGE IT
const char* password = "YOUR_WIFI_PASSWORD"; // CHANGE IT
AsyncWebServer server(80);
WebSocketsServer webSocket = WebSocketsServer(81); // WebSocket server on port 81
void webSocketEvent(uint8_t num, WStype_t type, uint8_t* payload, size_t length) {
switch (type) {
case WStype_DISCONNECTED:
Serial.printf("[%u] Disconnected!\n", num);
break;
case WStype_CONNECTED:
{
IPAddress ip = webSocket.remoteIP(num);
Serial.printf("[%u] Connected from %d.%d.%d.%d\n", num, ip[0], ip[1], ip[2], ip[3]);
}
break;
case WStype_TEXT:
//Serial.printf("[%u] Received text: %s\n", num, payload);
String angle = String((char*)payload);
int command = angle.toInt();
Serial.print("command: ");
Serial.println(command);
switch (command) {
case CMD_STOP:
Serial.println("Stop");
CAR_stop();
break;
case CMD_FORWARD:
Serial.println("Move Forward");
CAR_moveForward();
break;
case CMD_BACKWARD:
Serial.println("Move Backward");
CAR_moveBackward();
break;
case CMD_LEFT:
Serial.println("Turn Left");
CAR_turnLeft();
break;
case CMD_RIGHT:
Serial.println("Turn Right");
CAR_turnRight();
break;
default:
Serial.println("Unknown command");
}
break;
}
}
void setup() {
Serial.begin(9600);
pinMode(ENA_PIN, OUTPUT);
pinMode(IN1_PIN, OUTPUT);
pinMode(IN2_PIN, OUTPUT);
pinMode(IN3_PIN, OUTPUT);
pinMode(IN4_PIN, OUTPUT);
pinMode(ENB_PIN, OUTPUT);
digitalWrite(ENA_PIN, HIGH); // set full speed
digitalWrite(ENB_PIN, HIGH); // set full speed
// Connect to Wi-Fi
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(1000);
Serial.println("Connecting to WiFi...");
}
Serial.println("Connected to WiFi");
// Initialize WebSocket server
webSocket.begin();
webSocket.onEvent(webSocketEvent);
// Serve a basic HTML page with JavaScript to create the WebSocket connection
server.on("/", HTTP_GET, [](AsyncWebServerRequest* request) {
Serial.println("Web Server: received a web page request");
String html = HTML_CONTENT; // Use the HTML content from the servo_html.h file
request->send(200, "text/html", html);
});
server.begin();
Serial.print("ESP32 Web Server's IP address: ");
Serial.println(WiFi.localIP());
}
void loop() {
webSocket.loop();
// TO DO: Your code here
}
void CAR_moveForward() {
digitalWrite(IN1_PIN, HIGH);
digitalWrite(IN2_PIN, LOW);
digitalWrite(IN3_PIN, HIGH);
digitalWrite(IN4_PIN, LOW);
}
void CAR_moveBackward() {
digitalWrite(IN1_PIN, LOW);
digitalWrite(IN2_PIN, HIGH);
digitalWrite(IN3_PIN, LOW);
digitalWrite(IN4_PIN, HIGH);
}
void CAR_turnLeft() {
digitalWrite(IN1_PIN, HIGH);
digitalWrite(IN2_PIN, LOW);
digitalWrite(IN3_PIN, LOW);
digitalWrite(IN4_PIN, LOW);
}
void CAR_turnRight() {
digitalWrite(IN1_PIN, LOW);
digitalWrite(IN2_PIN, LOW);
digitalWrite(IN3_PIN, HIGH);
digitalWrite(IN4_PIN, LOW);
}
void CAR_stop() {
digitalWrite(IN1_PIN, LOW);
digitalWrite(IN2_PIN, LOW);
digitalWrite(IN3_PIN, LOW);
digitalWrite(IN4_PIN, LOW);
}
- Modify the WiFi information (SSID and password) in the code to match your own network credentials.
- Create the index.h file On Arduino IDE by:
- Either click on the button just below the serial monitor icon and choose New Tab, or use Ctrl+Shift+N keys.
- Give the file's name index.h and click OK button
- Copy the below code and paste it to the index.h.
- Now you have the code in two files: esp32io.com.ino and index.h
- Click Upload button on Arduino IDE to upload code to ESP32
- Open the Serial Monitor
- Check out the result on Serial Monitor.
- Take note of the IP address displayed, and enter this address into the address bar of a web browser on your smartphone or PC.
- You will see the webpage it as below:
- Click the CONNECT button to connect the webpage to ESP32 via WebSocket.
- Now you can control the car to turn left/right, move forward/backward via the web interface.
- If you modify the HTML content in the index.h and does not touch anything in esp32io.com.ino file, when you compile and upload code to ESP32, Arduino IDE will not update the HTML content.
- To make Arduino IDE update the HTML content in this case, make a change in the esp32io.com.ino file (e.g. adding empty line, add a comment....)
/*
* This ESP32 code is created by esp32io.com
*
* This ESP32 code is released in the public domain
*
* For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-controls-car-via-web
*/
const char *HTML_CONTENT = R"=====(
<!DOCTYPE html>
<html>
<head>
<title>ESP32 Control Car via Web</title>
<meta name="viewport" content="width=device-width, initial-scale=0.7, maximum-scale=1, user-scalable=no">
<style type="text/css">
body { text-align: center; font-size: 24px;}
button { text-align: center; font-size: 24px;}
#container {
margin-right: auto;
margin-left: auto;
width: 400px;
height: 400px;
position: relative;
margin-bottom: 10px;
}
div[class^='button'] { position: absolute; }
.button_up, .button_down { width:214px; height:104px;}
.button_left, .button_right { width:104px; height:214px;}
.button_stop { width:178px; height:178px;}
.button_up {
background: url('https://esp32io.com/images/tutorial/up_inactive.png') no-repeat;
background-size: contain;
left: 200px;
top: 0px;
transform: translateX(-50%);
}
.button_down {
background: url('https://esp32io.com/images/tutorial/down_inactive.png') no-repeat;
background-size: contain;
left:200px;
bottom: 0px;
transform: translateX(-50%);
}
.button_right {
background: url('https://esp32io.com/images/tutorial/right_inactive.png') no-repeat;
background-size: contain;
right: 0px;
top: 200px;
transform: translateY(-50%);
}
.button_left {
background: url('https://esp32io.com/images/tutorial/left_inactive.png') no-repeat;
background-size: contain;
left:0px;
top: 200px;
transform: translateY(-50%);
}
.button_stop {
background: url('https://esp32io.com/images/tutorial/stop_inactive.png') no-repeat;
background-size: contain;
left:200px;
top: 200px;
transform: translate(-50%, -50%);
}
</style>
<script>
var CMD_STOP = 0;
var CMD_FORWARD = 1;
var CMD_BACKWARD = 2;
var CMD_LEFT = 4;
var CMD_RIGHT = 8;
var img_name_lookup = {
[CMD_STOP]: "stop",
[CMD_FORWARD]: "up",
[CMD_BACKWARD]: "down",
[CMD_LEFT]: "left",
[CMD_RIGHT]: "right"
}
var ws = null;
function init()
{
var container = document.querySelector("#container");
container.addEventListener("touchstart", mouse_down);
container.addEventListener("touchend", mouse_up);
container.addEventListener("touchcancel", mouse_up);
container.addEventListener("mousedown", mouse_down);
container.addEventListener("mouseup", mouse_up);
container.addEventListener("mouseout", mouse_up);
}
function ws_onmessage(e_msg)
{
e_msg = e_msg || window.event; // MessageEvent
//alert("msg : " + e_msg.data);
}
function ws_onopen()
{
document.getElementById("ws_state").innerHTML = "OPEN";
document.getElementById("wc_conn").innerHTML = "Disconnect";
}
function ws_onclose()
{
document.getElementById("ws_state").innerHTML = "CLOSED";
document.getElementById("wc_conn").innerHTML = "Connect";
console.log("socket was closed");
ws.onopen = null;
ws.onclose = null;
ws.onmessage = null;
ws = null;
}
function wc_onclick()
{
if(ws == null)
{
ws = new WebSocket("ws://" + window.location.host + ":81");
document.getElementById("ws_state").innerHTML = "CONNECTING";
ws.onopen = ws_onopen;
ws.onclose = ws_onclose;
ws.onmessage = ws_onmessage;
}
else
ws.close();
}
function mouse_down(event)
{
if (event.target !== event.currentTarget)
{
var id = event.target.id;
send_command(id);
event.target.style.backgroundImage = "url('https://esp32io.com/images/tutorial/" + img_name_lookup[id] + "_active.png')";
}
event.stopPropagation();
event.preventDefault();
}
function mouse_up(event)
{
if (event.target !== event.currentTarget)
{
var id = event.target.id;
send_command(CMD_STOP);
event.target.style.backgroundImage = "url('https://esp32io.com/images/tutorial/" + img_name_lookup[id] + "_inactive.png')";
}
event.stopPropagation();
event.preventDefault();
}
function send_command(cmd)
{
if(ws != null)
if(ws.readyState == 1)
ws.send(cmd + "\r\n");
}
window.onload = init;
</script>
</head>
<body>
<h2>ESP32 - RC Car via Web</h2>
<div id="container">
<div id="0" class="button_stop"></div>
<div id="1" class="button_up"></div>
<div id="2" class="button_down"></div>
<div id="8" class="button_right"></div>
<div id="4" class="button_left"></div>
</div>
<p>
WebSocket : <span id="ws_state" style="color:blue">closed</span><br>
</p>
<button id="wc_conn" type="button" onclick="wc_onclick();">Connect</button>
<br>
<br>
<div class="sponsor">Sponsored by <a href="https://amazon.com/diyables">DIYables</a></div>
</body>
</html>
)=====";
COM6
Connecting to WiFi...
Connected to WiFi
ESP32 Web Server's IP address IP address: 192.168.0.2
Autoscroll
Clear output
9600 baud
Newline
To save the memory of ESP32, the images of the control buttons are NOT stored on ESP32. Instead, they are stored on the internet, so, your phone or PC need to have internet connection to load images for the web control page.
※ NOTE THAT:
Line-by-line Code Explanation
The above ESP32 code contains line-by-line explanation. Please read the comments in the code!