ESP32 - DIYables Bluetooth App Chat
Overview
The Bluetooth Chat example enables two-way text messaging between your ESP32 and a smartphone through the DIYables Bluetooth STEM app. Designed for ESP32 boards with support for both BLE (Bluetooth Low Energy) and Classic Bluetooth connections. Send and receive text messages in real time, implement custom command handling, and bridge Serial Monitor to Bluetooth — perfect for debugging, remote control, and interactive projects.
This example supports two Bluetooth modes:
- ESP32 BLE (Bluetooth Low Energy): Works on both Android and iOS
- ESP32 Classic Bluetooth: Works on Android only. iOS does not support Classic Bluetooth. Use BLE if you need iOS support.
Features
- Two-Way Messaging: Send and receive text messages in real time
- Echo Mode: Automatically echoes received messages back to the app
- Command Handling: Process custom text commands (ping, status, time, heap)
- Periodic Messages: Send automatic status updates at configurable intervals
- Serial-to-Bluetooth Bridge: Type messages in Serial Monitor and send them to the app
- BLE & Classic Bluetooth: Choose the Bluetooth mode that suits your project
- Cross-Platform: BLE mode works on both Android and iOS; Classic Bluetooth works on Android
- Low Power Option: BLE mode consumes less power than Classic Bluetooth
Hardware Used In This Tutorial
Or you can buy the following kits:
| 1 | × | DIYables ESP32 Starter Kit (ESP32 included) | |
| 1 | × | DIYables Sensor Kit (18 sensors/displays) |
Disclosure: Some of the links in this section are Amazon affiliate links, meaning we may earn a commission at no additional cost to you if you make a purchase through them. Additionally, some links direct you to products from our own brand, DIYables .
ESP32 Code
Quick Instructions
Follow these instructions step by step:
- If this is your first time using the ESP32, refer to the tutorial on setting up the environment for ESP32 in the Arduino IDE.
- Connect the ESP32 board to your computer using a USB cable.
- Launch the Arduino IDE on your computer.
- Select the appropriate ESP32 board and COM port.
- Navigate to the Libraries icon on the left bar of the Arduino IDE.
- Search "DIYables Bluetooth", then find the DIYables Bluetooth library by DIYables
- Click Install button to install the library.
- You will be asked for installing some other library dependencies
- Click Install All button to install all library dependencies.
Choose one of the two Bluetooth modes below depending on your needs:
ESP32 Classic Bluetooth Code (works with app on Android only)
Note: Classic Bluetooth is NOT supported on iOS. If you need iOS support, use the BLE code below.
- On Arduino IDE, Go to File Examples DIYables Bluetooth Esp32Bluetooth_Chat example, or copy the above code and paste it to the editor of Arduino IDE
/*
* DIYables Bluetooth Library - ESP32 Classic Bluetooth Chat Example
* Works with DIYables Bluetooth STEM app on Android
* Note: Classic Bluetooth is NOT supported on iOS. Use BLE examples for iOS support.
*
* This example demonstrates the Bluetooth Chat feature:
* - Two-way text messaging via Bluetooth
* - Receive messages from mobile app
* - Send messages to mobile app
*
* Compatible Boards:
* - ESP32 (all variants with Classic Bluetooth)
* - ESP32-WROOM-32
* - ESP32-DevKitC
* - ESP32-WROVER
*
* Note: Select "Huge APP (3MB No OTA/1MB SPIFFS)" partition scheme
* in Arduino IDE: Tools > Partition Scheme
*
* Setup:
* 1. Upload the sketch to your ESP32
* 2. Open Serial Monitor (115200 baud) to see connection status and messages
* 3. Use DIYables Bluetooth App to connect and chat
*
* Tutorial: https://diyables.io/bluetooth-app
* Author: DIYables
*/
#include <DIYables_BluetoothServer.h>
#include <DIYables_BluetoothChat.h>
#include <platforms/DIYables_Esp32Bluetooth.h>
// Create Bluetooth instances
DIYables_Esp32Bluetooth bluetooth("ESP32_Chat");
DIYables_BluetoothServer bluetoothServer(bluetooth);
// Create Chat app instance
DIYables_BluetoothChat bluetoothChat;
// Variables for periodic messages
unsigned long lastMessageTime = 0;
const unsigned long MESSAGE_INTERVAL = 10000; // Send message every 10 seconds
int messageCount = 0;
void setup() {
Serial.begin(115200);
delay(1000);
Serial.println("DIYables Bluetooth - ESP32 Chat Example");
// Initialize Bluetooth server with platform-specific implementation
bluetoothServer.begin();
// Add chat app to server
bluetoothServer.addApp(&bluetoothChat);
// Set up connection event callbacks
bluetoothServer.setOnConnected([]() {
Serial.println("Bluetooth connected!");
bluetoothChat.send("Hello! ESP32 is ready to chat.");
});
bluetoothServer.setOnDisconnected([]() {
Serial.println("Bluetooth disconnected!");
messageCount = 0;
});
// Set up callback for received chat messages
bluetoothChat.onChatMessage([](const String& message) {
Serial.print("Received: ");
Serial.println(message);
// Echo the message back
String response = "Echo: ";
response += message;
bluetoothChat.send(response);
// You can add custom command handling here
if (message.equalsIgnoreCase("ping")) {
bluetoothChat.send("pong!");
} else if (message.equalsIgnoreCase("status")) {
bluetoothChat.send("ESP32 is running normally");
} else if (message.equalsIgnoreCase("time")) {
String timeMsg = "Uptime: ";
timeMsg += String(millis() / 1000);
timeMsg += " seconds";
bluetoothChat.send(timeMsg);
} else if (message.equalsIgnoreCase("heap")) {
String heapMsg = "Free heap: ";
heapMsg += String(ESP.getFreeHeap());
heapMsg += " bytes";
bluetoothChat.send(heapMsg);
}
});
Serial.println("Waiting for Bluetooth connection...");
Serial.println("Type 'ping', 'status', 'time', or 'heap' in the app to test commands");
}
void loop() {
// Handle Bluetooth server communications
bluetoothServer.loop();
// Send periodic status message (only when connected)
if (bluetooth.isConnected() && millis() - lastMessageTime >= MESSAGE_INTERVAL) {
lastMessageTime = millis();
messageCount++;
String statusMsg = "Status update #";
statusMsg += String(messageCount);
statusMsg += " - All systems operational";
bluetoothChat.send(statusMsg);
Serial.print("Sent: ");
Serial.println(statusMsg);
}
// Optional: Read from Serial and send to Bluetooth
if (Serial.available()) {
String serialMsg = Serial.readStringUntil('\n');
serialMsg.trim();
if (serialMsg.length() > 0 && bluetooth.isConnected()) {
bluetoothChat.send(serialMsg);
Serial.print("Sent from Serial: ");
Serial.println(serialMsg);
}
}
delay(10);
}
- Click Upload button on Arduino IDE to upload code to ESP32
- Open the Serial Monitor
- Check out the result on Serial Monitor. It looks like the below:
COM6
DIYables Bluetooth - ESP32 Chat Example
Waiting for Bluetooth connection...
Type 'ping', 'status', 'time', or 'heap' in the app to test commands
Autoscroll
Clear output
9600 baud
Newline
ESP32 BLE Code (works with app on both Android and iOS)
- On Arduino IDE, Go to File Examples DIYables Bluetooth Esp32BLE_Chat example, or copy the above code and paste it to the editor of Arduino IDE
/*
* DIYables Bluetooth Library - ESP32 BLE Chat Example
* Works with DIYables Bluetooth STEM app on Android and iOS
*
* This example demonstrates the Bluetooth Chat feature:
* - Two-way text messaging via Bluetooth
* - Receive messages from mobile app
* - Send messages to mobile app
*
* Compatible Boards:
* - ESP32-WROOM-32
* - ESP32-DevKitC
* - ESP32-WROVER
* - ESP32-S3
* - ESP32-C3
* - Any ESP32 board supporting BLE
*
* Note: Select "Huge APP (3MB No OTA/1MB SPIFFS)" partition scheme
* in Arduino IDE: Tools > Partition Scheme
*
* Setup:
* 1. Upload the sketch to your ESP32
* 2. Open Serial Monitor (115200 baud) to see connection status and messages
* 3. Use DIYables Bluetooth App to connect and chat
*
* Tutorial: https://diyables.io/bluetooth-app
* Author: DIYables
*/
#include <DIYables_BluetoothServer.h>
#include <DIYables_BluetoothChat.h>
#include <platforms/DIYables_Esp32BLE.h>
// BLE Configuration
const char* DEVICE_NAME = "ESP32BLE_Chat";
const char* SERVICE_UUID = "19B10000-E8F2-537E-4F6C-D104768A1214";
const char* TX_UUID = "19B10001-E8F2-537E-4F6C-D104768A1214";
const char* RX_UUID = "19B10002-E8F2-537E-4F6C-D104768A1214";
// Create Bluetooth instances
DIYables_Esp32BLE bluetooth(DEVICE_NAME, SERVICE_UUID, TX_UUID, RX_UUID);
DIYables_BluetoothServer bluetoothServer(bluetooth);
// Create Chat app instance
DIYables_BluetoothChat bluetoothChat;
// Variables for periodic messages
unsigned long lastMessageTime = 0;
const unsigned long MESSAGE_INTERVAL = 10000; // Send message every 10 seconds
int messageCount = 0;
void setup() {
Serial.begin(115200);
delay(1000);
Serial.println("DIYables Bluetooth - ESP32 BLE Chat Example");
// Initialize Bluetooth server with platform-specific implementation
bluetoothServer.begin();
// Add chat app to server
bluetoothServer.addApp(&bluetoothChat);
// Set up connection event callbacks
bluetoothServer.setOnConnected([]() {
Serial.println("Bluetooth connected!");
bluetoothChat.send("Hello! ESP32 BLE is ready to chat.");
});
bluetoothServer.setOnDisconnected([]() {
Serial.println("Bluetooth disconnected!");
messageCount = 0;
});
// Set up callback for received chat messages
bluetoothChat.onChatMessage([](const String& message) {
Serial.print("Received: ");
Serial.println(message);
// Echo the message back
String response = "Echo: ";
response += message;
bluetoothChat.send(response);
// Custom command handling
if (message.equalsIgnoreCase("ping")) {
bluetoothChat.send("pong!");
} else if (message.equalsIgnoreCase("status")) {
bluetoothChat.send("ESP32 BLE is running normally");
} else if (message.equalsIgnoreCase("time")) {
String timeMsg = "Uptime: ";
timeMsg += String(millis() / 1000);
timeMsg += " seconds";
bluetoothChat.send(timeMsg);
} else if (message.equalsIgnoreCase("heap")) {
String heapMsg = "Free heap: ";
heapMsg += String(ESP.getFreeHeap());
heapMsg += " bytes";
bluetoothChat.send(heapMsg);
}
});
Serial.println("Waiting for Bluetooth connection...");
Serial.println("Type 'ping', 'status', 'time', or 'heap' in the app to test commands");
}
void loop() {
bluetoothServer.loop();
if (bluetooth.isConnected() && millis() - lastMessageTime >= MESSAGE_INTERVAL) {
lastMessageTime = millis();
messageCount++;
String statusMsg = "Status update #";
statusMsg += String(messageCount);
statusMsg += " - All systems operational";
bluetoothChat.send(statusMsg);
Serial.print("Sent: ");
Serial.println(statusMsg);
}
if (Serial.available()) {
String serialMsg = Serial.readStringUntil('\n');
serialMsg.trim();
if (serialMsg.length() > 0 && bluetooth.isConnected()) {
bluetoothChat.send(serialMsg);
Serial.print("Sent from Serial: ");
Serial.println(serialMsg);
}
}
delay(10);
}
- Click Upload button on Arduino IDE to upload code to ESP32
- Open the Serial Monitor
- Check out the result on Serial Monitor. It looks like the below:
COM6
DIYables Bluetooth - ESP32 BLE Chat Example
Waiting for Bluetooth connection...
Type 'ping', 'status', 'time', or 'heap' in the app to test commands
Autoscroll
Clear output
9600 baud
Newline
Mobile App
- If you are using the ESP32 Classic Bluetooth code, you need to pair the ESP32 with your Android phone before opening the app:
- Go to your phone's Settings > Bluetooth
- Make sure Bluetooth is turned on
- Your phone will scan for available devices
- Find and tap "ESP32_Chat" in the list of available devices
- Confirm the pairing request (no PIN required)
- Wait until it shows "Paired" under the device name
- If you are using the ESP32 BLE code, no pairing is needed. Just proceed to the next step.
- Open the DIYables Bluetooth App
- When opening the app for the first time, it will ask for permissions. Please grant the following:
- Nearby Devices permission (Android 12+) / Bluetooth permission (iOS) - required to scan and connect to Bluetooth devices
- Location permission (Android 11 and below only) - required by older Android versions to scan for BLE devices
- Make sure Bluetooth is turned on on your phone
- On the home screen, tap the Connect button. The app will scan for both BLE and Classic Bluetooth devices.
- Find and tap your device in the scan results to connect:
- For Classic Bluetooth: tap "ESP32_Chat"
- For BLE: tap "ESP32BLE_Chat"
- Once connected, the app automatically goes back to the home screen. Select the Chat app from the app menu.
Note: You can tap the settings icon on the home screen to hide/show apps on the home screen. For more details, see the DIYables Bluetooth App User Manual.
- Type a message in the text input and tap Send
Now look back at the Serial Monitor on Arduino IDE. You will see:
COM6
Bluetooth connected!
Received: Hello
Received: ping
Received: status
Sent: Status update #1 - All systems operational
Autoscroll
Clear output
9600 baud
Newline
- Type messages in the app and watch the real-time feedback in the Serial Monitor
- Try built-in commands: ping, status, time, heap
- You can also type messages in the Serial Monitor and they will be sent to the app
Creative Customization - Adapt the Code to Your Project
Receive Messages from App
Use the onChatMessage() callback to handle messages received from the app. You can define any custom command words that make sense for your project — the ESP32 will react accordingly:
bluetoothChat.onChatMessage([](const String& message) {
Serial.print("Received: ");
Serial.println(message);
// Process the message
if (message == "LED_ON") {
digitalWrite(2, HIGH);
bluetoothChat.send("LED turned ON");
} else if (message == "LED_OFF") {
digitalWrite(2, LOW);
bluetoothChat.send("LED turned OFF");
} else {
bluetoothChat.send("Unknown command: " + message);
}
});
You can add as many custom commands as you need by adding more else if blocks. For example, add RELAY_ON / RELAY_OFF to control a relay, or READ to trigger a sensor reading — any word you type in the app becomes a command.
Send Messages to App
You can send text messages from ESP32 to the app at any time:
// Send a simple text message
bluetoothChat.send("Hello from ESP32!");
// Send sensor data as text
float temperature = 25.3;
bluetoothChat.send("Temperature: " + String(temperature) + "°C");
// Send status updates
bluetoothChat.send("System ready");
Handle Connection Events
You can detect when the app connects or disconnects from the ESP32:
// Called when the app connects to ESP32
bluetoothServer.setOnConnected([]() {
Serial.println("Bluetooth connected!");
bluetoothChat.send("Welcome! ESP32 is ready to chat.");
});
// Called when the app disconnects from ESP32
bluetoothServer.setOnDisconnected([]() {
Serial.println("Bluetooth disconnected!");
});
// Check connection status anywhere in your code
if (bluetoothServer.isConnected()) {
bluetoothChat.send("Still connected!");
}
Serial-to-Bluetooth Bridge
Forward messages typed in Arduino IDE Serial Monitor to the Bluetooth app:
void loop() {
bluetoothServer.loop();
// Read from Serial and send to Bluetooth
if (Serial.available()) {
String serialMsg = Serial.readStringUntil('\n');
serialMsg.trim();
if (serialMsg.length() > 0 && bluetooth.isConnected()) {
bluetoothChat.send(serialMsg);
Serial.print("Sent from Serial: ");
Serial.println(serialMsg);
}
}
delay(10);
}
How to Use the Chat
App Interface Controls
The chat interface in the DIYables Bluetooth App provides:
- Message List: Scrollable list showing sent and received messages
- Text Input: Type your message at the bottom
- Send Button: Tap to send the typed message
- Auto-scroll: Automatically scrolls to the latest message
Built-in Commands
The example code includes these built-in commands:
- ping ? Responds with "pong!"
- status ? Reports ESP32 running status
- time ? Shows uptime in seconds
- heap ? Shows free heap memory in bytes
Programming Examples
Basic Echo Chat
void setup() {
// Set up chat callback
bluetoothChat.onChatMessage([](const String& message) {
Serial.print("Received: ");
Serial.println(message);
// Echo the message back
bluetoothChat.send("Echo: " + message);
});
}
Command-Based LED Control
const int LED_PIN = 2; // Built-in LED
const int RED_PIN = 16;
const int GREEN_PIN = 17;
const int BLUE_PIN = 18;
void setup() {
pinMode(LED_PIN, OUTPUT);
pinMode(RED_PIN, OUTPUT);
pinMode(GREEN_PIN, OUTPUT);
pinMode(BLUE_PIN, OUTPUT);
bluetoothChat.onChatMessage([](const String& message) {
String cmd = message;
cmd.toUpperCase();
if (cmd == "LED ON") {
digitalWrite(LED_PIN, HIGH);
bluetoothChat.send("LED is now ON");
} else if (cmd == "LED OFF") {
digitalWrite(LED_PIN, LOW);
bluetoothChat.send("LED is now OFF");
} else if (cmd == "RED") {
digitalWrite(RED_PIN, HIGH);
digitalWrite(GREEN_PIN, LOW);
digitalWrite(BLUE_PIN, LOW);
bluetoothChat.send("Red LED activated");
} else if (cmd == "GREEN") {
digitalWrite(RED_PIN, LOW);
digitalWrite(GREEN_PIN, HIGH);
digitalWrite(BLUE_PIN, LOW);
bluetoothChat.send("Green LED activated");
} else if (cmd == "BLUE") {
digitalWrite(RED_PIN, LOW);
digitalWrite(GREEN_PIN, LOW);
digitalWrite(BLUE_PIN, HIGH);
bluetoothChat.send("Blue LED activated");
} else if (cmd == "OFF") {
digitalWrite(RED_PIN, LOW);
digitalWrite(GREEN_PIN, LOW);
digitalWrite(BLUE_PIN, LOW);
bluetoothChat.send("All LEDs off");
} else if (cmd == "HELP") {
bluetoothChat.send("Commands: LED ON, LED OFF, RED, GREEN, BLUE, OFF, HELP");
} else {
bluetoothChat.send("Unknown command. Type HELP for list.");
}
});
}
Sensor Query System
#include <DHT.h>
DHT dht(4, DHT22);
void setup() {
dht.begin();
bluetoothChat.onChatMessage([](const String& message) {
String cmd = message;
cmd.toUpperCase();
if (cmd == "TEMP") {
float temp = dht.readTemperature();
if (!isnan(temp)) {
bluetoothChat.send("Temperature: " + String(temp, 1) + " °C");
} else {
bluetoothChat.send("Error reading temperature sensor");
}
} else if (cmd == "HUMIDITY") {
float hum = dht.readHumidity();
if (!isnan(hum)) {
bluetoothChat.send("Humidity: " + String(hum, 1) + " %");
} else {
bluetoothChat.send("Error reading humidity sensor");
}
} else if (cmd == "ALL") {
float temp = dht.readTemperature();
float hum = dht.readHumidity();
bluetoothChat.send("Temp: " + String(temp, 1) + "°C | Humidity: " + String(hum, 1) + "%");
} else if (cmd == "HELP") {
bluetoothChat.send("Commands: TEMP, HUMIDITY, ALL, HELP");
}
});
}
Relay Control with Confirmation
const int RELAY_1 = 16;
const int RELAY_2 = 17;
bool relay1State = false;
bool relay2State = false;
void setup() {
pinMode(RELAY_1, OUTPUT);
pinMode(RELAY_2, OUTPUT);
digitalWrite(RELAY_1, LOW);
digitalWrite(RELAY_2, LOW);
bluetoothChat.onChatMessage([](const String& message) {
String cmd = message;
cmd.toUpperCase();
if (cmd == "R1 ON") {
digitalWrite(RELAY_1, HIGH);
relay1State = true;
bluetoothChat.send("Relay 1: ON");
} else if (cmd == "R1 OFF") {
digitalWrite(RELAY_1, LOW);
relay1State = false;
bluetoothChat.send("Relay 1: OFF");
} else if (cmd == "R2 ON") {
digitalWrite(RELAY_2, HIGH);
relay2State = true;
bluetoothChat.send("Relay 2: ON");
} else if (cmd == "R2 OFF") {
digitalWrite(RELAY_2, LOW);
relay2State = false;
bluetoothChat.send("Relay 2: OFF");
} else if (cmd == "STATUS") {
bluetoothChat.send("Relay 1: " + String(relay1State ? "ON" : "OFF"));
bluetoothChat.send("Relay 2: " + String(relay2State ? "ON" : "OFF"));
} else if (cmd == "HELP") {
bluetoothChat.send("Commands: R1 ON, R1 OFF, R2 ON, R2 OFF, STATUS, HELP");
}
});
}
Advanced Programming Techniques
Periodic Status Updates
unsigned long lastMessageTime = 0;
const unsigned long MESSAGE_INTERVAL = 10000; // 10 seconds
void loop() {
bluetoothServer.loop();
// Send periodic status updates (only when connected)
if (bluetooth.isConnected() && millis() - lastMessageTime >= MESSAGE_INTERVAL) {
lastMessageTime = millis();
messageCount++;
String statusMsg = "Status update #" + String(messageCount);
statusMsg += " - Uptime: " + String(millis() / 1000) + "s";
statusMsg += " - Heap: " + String(ESP.getFreeHeap()) + " bytes";
bluetoothChat.send(statusMsg);
}
delay(10);
}
Message Logging
// Log all messages to Serial with timestamps
bluetoothChat.onChatMessage([](const String& message) {
unsigned long timestamp = millis() / 1000;
Serial.print("[");
Serial.print(timestamp);
Serial.print("s] Received: ");
Serial.println(message);
// Process and respond
String response = processCommand(message);
bluetoothChat.send(response);
Serial.print("[");
Serial.print(millis() / 1000);
Serial.print("s] Sent: ");
Serial.println(response);
});
String processCommand(const String& cmd) {
if (cmd.equalsIgnoreCase("ping")) return "pong!";
if (cmd.equalsIgnoreCase("status")) return "All systems operational";
if (cmd.equalsIgnoreCase("time")) return "Uptime: " + String(millis() / 1000) + "s";
return "Echo: " + cmd;
}
Command Parser with Arguments
bluetoothChat.onChatMessage([](const String& message) {
// Parse command and argument (format: "COMMAND ARG")
int spaceIndex = message.indexOf(' ');
String command, argument;
if (spaceIndex > 0) {
command = message.substring(0, spaceIndex);
argument = message.substring(spaceIndex + 1);
} else {
command = message;
argument = "";
}
command.toUpperCase();
if (command == "PWM") {
int value = argument.toInt();
value = constrain(value, 0, 255);
analogWrite(16, value);
bluetoothChat.send("PWM set to " + String(value));
} else if (command == "DELAY") {
int ms = argument.toInt();
bluetoothChat.send("Waiting " + String(ms) + "ms...");
delay(ms);
bluetoothChat.send("Done!");
} else if (command == "PIN") {
// Format: "PIN 13 HIGH" or "PIN 13 LOW"
int secondSpace = argument.indexOf(' ');
if (secondSpace > 0) {
int pin = argument.substring(0, secondSpace).toInt();
String state = argument.substring(secondSpace + 1);
state.toUpperCase();
digitalWrite(pin, state == "HIGH" ? HIGH : LOW);
bluetoothChat.send("Pin " + String(pin) + " set " + state);
}
}
});
Hardware Integration Examples
Servo Control via Chat
#include <ESP32Servo.h>
Servo myServo;
const int SERVO_PIN = 13;
void setup() {
myServo.attach(SERVO_PIN);
bluetoothChat.onChatMessage([](const String& message) {
// Accept angle commands like "90" or "SERVO 90"
String cmd = message;
cmd.toUpperCase();
int angle = -1;
if (cmd.startsWith("SERVO ")) {
angle = cmd.substring(6).toInt();
} else {
angle = cmd.toInt();
if (angle == 0 && cmd != "0") angle = -1; // Not a number
}
if (angle >= 0 && angle <= 180) {
myServo.write(angle);
bluetoothChat.send("Servo moved to " + String(angle) + "°");
} else if (cmd == "SWEEP") {
bluetoothChat.send("Sweeping servo...");
for (int a = 0; a <= 180; a += 5) {
myServo.write(a);
delay(30);
}
for (int a = 180; a >= 0; a -= 5) {
myServo.write(a);
delay(30);
}
bluetoothChat.send("Sweep complete");
}
});
}
Motor Control via Chat
const int MOTOR_PWM = 16;
const int MOTOR_DIR1 = 18;
const int MOTOR_DIR2 = 19;
void setup() {
pinMode(MOTOR_PWM, OUTPUT);
pinMode(MOTOR_DIR1, OUTPUT);
pinMode(MOTOR_DIR2, OUTPUT);
bluetoothChat.onChatMessage([](const String& message) {
String cmd = message;
cmd.toUpperCase();
if (cmd == "FORWARD") {
digitalWrite(MOTOR_DIR1, HIGH);
digitalWrite(MOTOR_DIR2, LOW);
analogWrite(MOTOR_PWM, 200);
bluetoothChat.send("Motor running forward");
} else if (cmd == "REVERSE") {
digitalWrite(MOTOR_DIR1, LOW);
digitalWrite(MOTOR_DIR2, HIGH);
analogWrite(MOTOR_PWM, 200);
bluetoothChat.send("Motor running reverse");
} else if (cmd == "STOP") {
analogWrite(MOTOR_PWM, 0);
bluetoothChat.send("Motor stopped");
} else if (cmd.startsWith("SPEED ")) {
int speed = cmd.substring(6).toInt();
speed = constrain(speed, 0, 255);
analogWrite(MOTOR_PWM, speed);
bluetoothChat.send("Motor speed: " + String(speed));
}
});
}
BLE vs Classic Bluetooth - Which to Choose?
| Feature | BLE (Esp32BLE_Chat) | Classic Bluetooth (Esp32Bluetooth_Chat) |
|---|---|---|
| iOS Support | ? Yes | ? No |
| Android Support | ? Yes | ? Yes |
| Power Consumption | Low | Higher |
| Range | ~30-100m | ~10-100m |
| Data Rate | Lower | Higher |
| Pairing Required | No (auto-connect) | Yes (manual pairing) |
| Best For | Battery-powered, cross-platform | High throughput, Android-only |
Troubleshooting
Common Issues
1. Cannot find the device in the app
- Make sure the ESP32 is powered on and the sketch is uploaded
- For BLE: Ensure your phone's Bluetooth and Location are enabled
- For Classic Bluetooth: Pair the device first in phone's Bluetooth settings
- Check that the correct partition scheme is selected (Huge APP)
2. Messages not appearing in the app
- Check Bluetooth connection status in the app
- Verify connection in Serial Monitor
- Ensure messages are being sent with bluetoothChat.send()
- Try disconnecting and reconnecting
3. Echo messages not working
- Verify the onChatMessage() callback is set up correctly
- Check Serial Monitor for received messages
- Ensure the chat app screen is selected in the mobile app
4. Connection drops frequently
- Move closer to the ESP32 (reduce distance)
- For BLE: Check for interference from other BLE devices
- For Classic Bluetooth: Ensure stable power supply to ESP32
- Check Serial Monitor for disconnect/reconnect messages
5. Serial-to-Bluetooth bridge not working
- Ensure Serial Monitor baud rate is 115200
- Set line ending to "Newline" in Serial Monitor
- Check that bluetooth.isConnected() returns true
- Verify the Serial.available() code is in the loop()
6. Sketch too large / not enough space
- In Arduino IDE, go to Tools > Partition Scheme and select "Huge APP (3MB No OTA/1MB SPIFFS)" or "No OTA (Large APP)"
- The default partition scheme only provides ~1.2MB for app code, which is not enough for Bluetooth libraries
- This setting gives ~3MB by sacrificing the OTA (over-the-air update) partition
Debug Tips
Add comprehensive debugging:
void debugChatMessage(const String& message) {
Serial.println("=== Chat Debug ===");
Serial.println("Message: " + message);
Serial.println("Length: " + String(message.length()));
Serial.println("Free Heap: " + String(ESP.getFreeHeap()));
Serial.println("==================");
}
Project Ideas
Remote Control Projects
- Voice-command-style text control for robots
- Home automation command center
- Wireless relay control with text feedback
- Remote servo positioning via chat
Monitoring Projects
- Remote sensor data querying
- System health check via chat commands
- Data logging with Bluetooth feedback
- Remote debugging and diagnostics
Interactive Projects
- Quiz or trivia game via Bluetooth chat
- Interactive tutorials with step-by-step instructions
- Chatbot for ESP32 project information
- Remote configuration tool
Education Projects
- Learn Bluetooth communication basics
- Practice string parsing and command handling
- Understand client-server messaging patterns
- Build custom communication protocols
Integration with Other Bluetooth Apps
Combine with Bluetooth Monitor
Use Chat for commands and Monitor for continuous output:
bluetoothChat.onChatMessage([](const String& message) {
if (message.equalsIgnoreCase("start")) {
monitoring = true;
bluetoothChat.send("Monitoring started");
} else if (message.equalsIgnoreCase("stop")) {
monitoring = false;
bluetoothChat.send("Monitoring stopped");
}
});
// In loop: send data to monitor when active
if (monitoring) {
bluetoothMonitor.send("Sensor: " + String(analogRead(34)));
}
Combine with Bluetooth Slider
Use Chat to set slider presets and Slider for fine control:
bluetoothChat.onChatMessage([](const String& message) {
if (message.equalsIgnoreCase("preset1")) {
currentSlider1 = 25;
currentSlider2 = 75;
bluetoothSlider.send(currentSlider1, currentSlider2);
bluetoothChat.send("Applied Preset 1: 25%, 75%");
} else if (message.equalsIgnoreCase("preset2")) {
currentSlider1 = 50;
currentSlider2 = 50;
bluetoothSlider.send(currentSlider1, currentSlider2);
bluetoothChat.send("Applied Preset 2: 50%, 50%");
}
});
Next Steps
After mastering the Bluetooth Chat example, try:
- Bluetooth Monitor - For one-way data streaming to the app
- Bluetooth Slider - For analog-like value control
- Bluetooth Digital Pins - For discrete on/off control
- Multiple Bluetooth Apps - Combining chat with other controls
Support
For additional help:
- Check the API Reference documentation
- Visit DIYables tutorials
- Arduino community forums