ESP32 - DIYables Bluetooth App Monitor
Overview
The Bluetooth Monitor example provides a wireless serial monitor interface accessible through the DIYables Bluetooth STEM app. Designed for ESP32 boards with support for both BLE (Bluetooth Low Energy) and Classic Bluetooth connections. Stream real-time status messages to the app, receive and process text commands, display system information, and debug your projects wirelessly — perfect for untethered monitoring, remote debugging, and system status displays.
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
- Real-Time Streaming: Send continuous status messages to the app display
- Command Processing: Receive and handle text commands from the app
- System Monitoring: Display uptime, free heap, CPU info, and more
- LED Control: Built-in LED ON/OFF commands for quick testing
- Periodic Updates: Automatic heartbeat and status messages at configurable intervals
- 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_Monitor example, or copy the above code and paste it to the editor of Arduino IDE
/*
* DIYables Bluetooth Library - ESP32 Classic Bluetooth Monitor 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 Monitor feature:
* - Send real-time status messages to the mobile app
* - Display system information and sensor readings
* - Receive and process commands from the app
* - Perfect for debugging and system monitoring
*
* 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
* 3. Use DIYables Bluetooth App to connect and view monitor output
*
* Tutorial: https://diyables.io/bluetooth-app
* Author: DIYables
*/
#include <DIYables_BluetoothServer.h>
#include <DIYables_BluetoothMonitor.h>
#include <platforms/DIYables_Esp32Bluetooth.h>
// Create Bluetooth instances
DIYables_Esp32Bluetooth bluetooth("ESP32_Monitor");
DIYables_BluetoothServer bluetoothServer(bluetooth);
// Create Monitor app instance
DIYables_BluetoothMonitor bluetoothMonitor;
// Variables for demo
unsigned long lastUpdate = 0;
const unsigned long UPDATE_INTERVAL = 3000; // Send update every 3 seconds
int messageCount = 0;
bool ledState = false;
// ESP32 built-in LED (may vary by board)
const int LED_PIN = 2;
void setup() {
Serial.begin(115200);
delay(1000);
Serial.println("DIYables Bluetooth - ESP32 Monitor Example");
// Initialize LED
pinMode(LED_PIN, OUTPUT);
digitalWrite(LED_PIN, LOW);
// Initialize Bluetooth server with platform-specific implementation
bluetoothServer.begin();
// Add monitor app to server
bluetoothServer.addApp(&bluetoothMonitor);
// Set up connection event callbacks
bluetoothServer.setOnConnected([]() {
Serial.println("Bluetooth connected!");
bluetoothMonitor.send("=== ESP32 Monitor Connected ===");
bluetoothMonitor.send("System Ready");
bluetoothMonitor.send("Type HELP for available commands");
bluetoothMonitor.send("");
});
bluetoothServer.setOnDisconnected([]() {
Serial.println("Bluetooth disconnected!");
});
// Set up message handler for incoming commands
bluetoothMonitor.onMonitorMessage([](const String& message) {
Serial.print("Received command: ");
Serial.println(message);
handleCommand(message);
});
Serial.println("Waiting for Bluetooth connection...");
}
void handleCommand(const String& cmd) {
if (cmd == "HELP") {
bluetoothMonitor.send("Available Commands:");
bluetoothMonitor.send(" LED_ON - Turn LED on");
bluetoothMonitor.send(" LED_OFF - Turn LED off");
bluetoothMonitor.send(" STATUS - Show system status");
bluetoothMonitor.send(" HEAP - Show memory info");
bluetoothMonitor.send(" CLEAR - Clear monitor (if supported)");
bluetoothMonitor.send(" HELP - Show this help");
}
else if (cmd == "LED_ON") {
digitalWrite(LED_PIN, HIGH);
ledState = true;
bluetoothMonitor.send("✓ LED turned ON");
}
else if (cmd == "LED_OFF") {
digitalWrite(LED_PIN, LOW);
ledState = false;
bluetoothMonitor.send("✓ LED turned OFF");
}
else if (cmd == "STATUS") {
showStatus();
}
else if (cmd == "HEAP") {
bluetoothMonitor.send("=== Memory Info ===");
bluetoothMonitor.send("Free Heap: " + String(ESP.getFreeHeap()) + " bytes");
bluetoothMonitor.send("Min Free Heap: " + String(ESP.getMinFreeHeap()) + " bytes");
bluetoothMonitor.send("Heap Size: " + String(ESP.getHeapSize()) + " bytes");
bluetoothMonitor.send("===================");
}
else if (cmd == "CLEAR") {
bluetoothMonitor.send("");
}
else {
bluetoothMonitor.send("✗ Unknown command: " + cmd);
bluetoothMonitor.send("Type HELP for available commands");
}
}
void showStatus() {
bluetoothMonitor.send("=== System Status ===");
// LED Status
bluetoothMonitor.send("LED State: " + String(ledState ? "ON" : "OFF"));
// Uptime
unsigned long uptime = millis() / 1000;
bluetoothMonitor.send("Uptime: " + String(uptime / 3600) + "h " + String((uptime % 3600) / 60) + "m " + String(uptime % 60) + "s");
// ESP32-specific info
bluetoothMonitor.send("Free Heap: " + String(ESP.getFreeHeap()) + " bytes");
bluetoothMonitor.send("CPU Freq: " + String(ESP.getCpuFreqMHz()) + " MHz");
bluetoothMonitor.send("Chip Model: " + String(ESP.getChipModel()));
// Messages sent
bluetoothMonitor.send("Messages Sent: " + String(messageCount));
bluetoothMonitor.send("====================");
}
void sendPeriodicUpdate() {
messageCount++;
// Example of different message types
if (messageCount % 3 == 0) {
bluetoothMonitor.send("[INFO] Heartbeat #" + String(messageCount));
}
else if (messageCount % 5 == 0) {
bluetoothMonitor.send("[HEAP] Free: " + String(ESP.getFreeHeap()) + " bytes");
}
else {
bluetoothMonitor.send("[TIME] Uptime: " + String(millis() / 1000) + "s");
}
Serial.print("Sent update #");
Serial.println(messageCount);
}
void loop() {
// Handle Bluetooth server communications
bluetoothServer.loop();
// Send periodic updates (only when connected)
if (bluetooth.isConnected() && millis() - lastUpdate >= UPDATE_INTERVAL) {
lastUpdate = millis();
sendPeriodicUpdate();
}
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 Monitor Example
Waiting for Bluetooth connection...
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_Monitor example, or copy the above code and paste it to the editor of Arduino IDE
/*
* DIYables Bluetooth Library - ESP32 BLE Monitor Example
* Works with DIYables Bluetooth STEM app on Android and iOS
*
* This example demonstrates the Bluetooth Monitor feature:
* - Send real-time status messages to the mobile app
* - Display system information and sensor readings
* - Receive and process commands from the app
* - Perfect for debugging and system monitoring
*
* 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
* 3. Use DIYables Bluetooth App to connect and view monitor output
*
* Tutorial: https://diyables.io/bluetooth-app
* Author: DIYables
*/
#include <DIYables_BluetoothServer.h>
#include <DIYables_BluetoothMonitor.h>
#include <platforms/DIYables_Esp32BLE.h>
// BLE Configuration
const char* DEVICE_NAME = "ESP32BLE_Monitor";
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 Monitor app instance
DIYables_BluetoothMonitor bluetoothMonitor;
// Variables for demo
unsigned long lastUpdate = 0;
const unsigned long UPDATE_INTERVAL = 3000;
int messageCount = 0;
bool ledState = false;
void setup() {
Serial.begin(115200);
delay(1000);
Serial.println("DIYables Bluetooth - ESP32 BLE Monitor Example");
// Initialize built-in LED
pinMode(2, OUTPUT); // ESP32 built-in LED is usually on GPIO 2
digitalWrite(2, LOW);
// Initialize Bluetooth server with platform-specific implementation
bluetoothServer.begin();
// Add monitor app to server
bluetoothServer.addApp(&bluetoothMonitor);
// Set up connection event callbacks
bluetoothServer.setOnConnected([]() {
Serial.println("Bluetooth connected!");
bluetoothMonitor.send("=== ESP32 BLE Monitor Connected ===");
bluetoothMonitor.send("System Ready");
bluetoothMonitor.send("Type HELP for available commands");
bluetoothMonitor.send("");
});
bluetoothServer.setOnDisconnected([]() {
Serial.println("Bluetooth disconnected!");
});
// Set up message handler for incoming commands
bluetoothMonitor.onMonitorMessage([](const String& message) {
Serial.print("Received command: ");
Serial.println(message);
handleCommand(message);
});
Serial.println("Waiting for Bluetooth connection...");
}
void handleCommand(const String& cmd) {
if (cmd == "HELP") {
bluetoothMonitor.send("Available Commands:");
bluetoothMonitor.send(" LED_ON - Turn LED on");
bluetoothMonitor.send(" LED_OFF - Turn LED off");
bluetoothMonitor.send(" STATUS - Show system status");
bluetoothMonitor.send(" HEAP - Show free heap memory");
bluetoothMonitor.send(" HELP - Show this help");
}
else if (cmd == "LED_ON") {
digitalWrite(2, HIGH);
ledState = true;
bluetoothMonitor.send("LED turned ON");
}
else if (cmd == "LED_OFF") {
digitalWrite(2, LOW);
ledState = false;
bluetoothMonitor.send("LED turned OFF");
}
else if (cmd == "STATUS") {
showStatus();
}
else if (cmd == "HEAP") {
bluetoothMonitor.send("Free heap: " + String(ESP.getFreeHeap()) + " bytes");
}
else {
bluetoothMonitor.send("Unknown command: " + cmd);
bluetoothMonitor.send("Type HELP for available commands");
}
}
void showStatus() {
bluetoothMonitor.send("=== System Status ===");
bluetoothMonitor.send("LED State: " + String(ledState ? "ON" : "OFF"));
unsigned long uptime = millis() / 1000;
bluetoothMonitor.send("Uptime: " + String(uptime / 3600) + "h " + String((uptime % 3600) / 60) + "m " + String(uptime % 60) + "s");
bluetoothMonitor.send("Free Heap: " + String(ESP.getFreeHeap()) + " bytes");
bluetoothMonitor.send("Messages Sent: " + String(messageCount));
bluetoothMonitor.send("====================");
}
void sendPeriodicUpdate() {
messageCount++;
if (messageCount % 3 == 0) {
bluetoothMonitor.send("[INFO] Heartbeat #" + String(messageCount));
}
else if (messageCount % 5 == 0) {
bluetoothMonitor.send("[HEAP] Free: " + String(ESP.getFreeHeap()) + " bytes");
}
else {
bluetoothMonitor.send("[TIME] Uptime: " + String(millis() / 1000) + "s");
}
Serial.print("Sent update #");
Serial.println(messageCount);
}
void loop() {
bluetoothServer.loop();
if (bluetooth.isConnected() && millis() - lastUpdate >= UPDATE_INTERVAL) {
lastUpdate = millis();
sendPeriodicUpdate();
}
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 Monitor Example
Waiting for Bluetooth connection...
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_Monitor" 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_Monitor"
- For BLE: tap "ESP32BLE_Monitor"
- Once connected, the app automatically goes back to the home screen. Select the Monitor 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.
- You will see status messages streaming in the monitor display
- Type LED_ON in the input field and tap Send — the built-in LED on the ESP32 will turn ON, and the monitor will display a confirmation message
Now look back at the Serial Monitor on Arduino IDE. You will see:
COM6
Bluetooth connected!
Sent update #1
Sent update #2
Received command: HELP
Received command: STATUS
Autoscroll
Clear output
9600 baud
Newline
- Type commands in the app (HELP, STATUS, LED_ON, LED_OFF, HEAP) and watch the responses
Creative Customization - Adapt the Code to Your Project
Send Messages to App
Use the send() method to stream text messages to the monitor display:
// Send simple messages
bluetoothMonitor.send("System initialized");
bluetoothMonitor.send("Sensor reading: 25.3°C");
// Send formatted data
bluetoothMonitor.send("[INFO] Heartbeat #" + String(count));
bluetoothMonitor.send("[WARN] Temperature high: " + String(temp) + "°C");
bluetoothMonitor.send("[ERROR] Sensor disconnected");
// Send system information
bluetoothMonitor.send("Free Heap: " + String(ESP.getFreeHeap()) + " bytes");
bluetoothMonitor.send("Uptime: " + String(millis() / 1000) + " seconds");
Receive Commands from App
Use the onMonitorMessage() callback to receive commands typed in the Monitor app and react to them:
bluetoothMonitor.onMonitorMessage([](const String& message) {
Serial.print("Received command: ");
Serial.println(message);
if (message == "HELP") {
bluetoothMonitor.send("Available Commands:");
bluetoothMonitor.send(" LED_ON - Turn LED on");
bluetoothMonitor.send(" LED_OFF - Turn LED off");
bluetoothMonitor.send(" STATUS - Show system status");
bluetoothMonitor.send(" HEAP - Show memory info");
} else if (message == "LED_ON") {
digitalWrite(LED_BUILTIN, HIGH);
bluetoothMonitor.send("LED turned ON");
} else if (message == "LED_OFF") {
digitalWrite(LED_BUILTIN, LOW);
bluetoothMonitor.send("LED turned OFF");
} else if (message == "STATUS") {
bluetoothMonitor.send("System is running normally");
bluetoothMonitor.send("Uptime: " + String(millis() / 1000) + "s");
} else if (message == "HEAP") {
bluetoothMonitor.send("Free Heap: " + String(ESP.getFreeHeap()) + " bytes");
} else {
bluetoothMonitor.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.
Handle Connection Events
You can detect when the app connects or disconnects from the ESP32:
bluetoothServer.setOnConnected([]() {
Serial.println("Bluetooth connected!");
bluetoothMonitor.send("=== ESP32 Monitor Connected ===");
bluetoothMonitor.send("System Ready");
bluetoothMonitor.send("Type HELP for available commands");
});
bluetoothServer.setOnDisconnected([]() {
Serial.println("Bluetooth disconnected!");
});
if (bluetoothServer.isConnected()) {
bluetoothMonitor.send("Status update");
}
How to Use the Monitor
App Interface Controls
The monitor interface in the DIYables Bluetooth App provides:
- Message Display: Scrollable list of received messages with auto-scroll
- Text Input: Type commands at the bottom
- Send Button: Tap to send the typed command to ESP32
Built-in Commands
The example code includes these built-in commands:
- HELP ? Shows all available commands
- LED_ON ? Turns the built-in LED on
- LED_OFF ? Turns the built-in LED off
- STATUS ? Shows system status (LED state, uptime, heap, messages sent)
- HEAP ? Shows detailed memory information
Programming Examples
Basic Status Streaming
unsigned long lastUpdate = 0;
const unsigned long UPDATE_INTERVAL = 3000;
int messageCount = 0;
void loop() {
bluetoothServer.loop();
if (bluetooth.isConnected() && millis() - lastUpdate >= UPDATE_INTERVAL) {
lastUpdate = millis();
messageCount++;
// Rotate between different status messages
if (messageCount % 3 == 0) {
bluetoothMonitor.send("[INFO] Heartbeat #" + String(messageCount));
} else if (messageCount % 5 == 0) {
bluetoothMonitor.send("[HEAP] Free: " + String(ESP.getFreeHeap()) + " bytes");
} else {
bluetoothMonitor.send("[TIME] Uptime: " + String(millis() / 1000) + "s");
}
}
delay(10);
}
Sensor Data Logger
#include <DHT.h>
DHT dht(4, DHT22);
unsigned long lastSensorRead = 0;
const unsigned long SENSOR_INTERVAL = 5000;
void setup() {
dht.begin();
bluetoothMonitor.onMonitorMessage([](const String& message) {
if (message == "READ") {
readAndSendSensorData();
} else if (message == "INTERVAL") {
bluetoothMonitor.send("Sensor interval: " + String(SENSOR_INTERVAL / 1000) + "s");
}
});
}
void readAndSendSensorData() {
float temp = dht.readTemperature();
float hum = dht.readHumidity();
if (!isnan(temp) && !isnan(hum)) {
bluetoothMonitor.send("Temp: " + String(temp, 1) + "°C | Humidity: " + String(hum, 1) + "%");
} else {
bluetoothMonitor.send("[ERROR] Failed to read sensor");
}
}
void loop() {
bluetoothServer.loop();
if (bluetooth.isConnected() && millis() - lastSensorRead >= SENSOR_INTERVAL) {
lastSensorRead = millis();
readAndSendSensorData();
}
delay(10);
}
Multi-Sensor Dashboard
void sendDashboard() {
bluetoothMonitor.send("========== DASHBOARD ==========");
bluetoothMonitor.send("Temp: " + String(readTemperature(), 1) + "°C");
bluetoothMonitor.send("Humidity: " + String(readHumidity(), 0) + "%");
bluetoothMonitor.send("Light: " + String(analogRead(34)));
bluetoothMonitor.send("Battery: " + String(readBatteryVoltage(), 2) + "V");
bluetoothMonitor.send("Heap: " + String(ESP.getFreeHeap()) + " bytes");
unsigned long uptime = millis() / 1000;
bluetoothMonitor.send("Uptime: " + String(uptime / 3600) + "h " +
String((uptime % 3600) / 60) + "m " +
String(uptime % 60) + "s");
bluetoothMonitor.send("===============================");
}
GPIO Pin Monitor
const int MONITOR_PINS[] = {16, 17, 18, 19, 21, 22};
const int NUM_PINS = 6;
int lastPinStates[6] = {0};
void setup() {
for (int i = 0; i < NUM_PINS; i++) {
pinMode(MONITOR_PINS[i], INPUT_PULLUP);
lastPinStates[i] = digitalRead(MONITOR_PINS[i]);
}
bluetoothMonitor.onMonitorMessage([](const String& message) {
if (message == "PINS") {
for (int i = 0; i < NUM_PINS; i++) {
int state = digitalRead(MONITOR_PINS[i]);
bluetoothMonitor.send("Pin " + String(MONITOR_PINS[i]) + ": " +
String(state ? "HIGH" : "LOW"));
}
}
});
}
void loop() {
bluetoothServer.loop();
// Detect pin changes and report
for (int i = 0; i < NUM_PINS; i++) {
int state = digitalRead(MONITOR_PINS[i]);
if (state != lastPinStates[i]) {
lastPinStates[i] = state;
if (bluetooth.isConnected()) {
bluetoothMonitor.send("[PIN] GPIO " + String(MONITOR_PINS[i]) +
" changed to " + String(state ? "HIGH" : "LOW"));
}
}
}
delay(10);
}
Advanced Programming Techniques
Categorized Logging
enum LogLevel { LOG_INFO, LOG_WARN, LOG_ERROR, LOG_DEBUG };
void sendLog(LogLevel level, const String& message) {
String prefix;
switch (level) {
case LOG_INFO: prefix = "[INFO] "; break;
case LOG_WARN: prefix = "[WARN] "; break;
case LOG_ERROR: prefix = "[ERROR] "; break;
case LOG_DEBUG: prefix = "[DEBUG] "; break;
}
bluetoothMonitor.send(prefix + message);
}
// Usage:
sendLog(LOG_INFO, "System started");
sendLog(LOG_WARN, "Battery low: " + String(voltage, 2) + "V");
sendLog(LOG_ERROR, "Sensor read failed");
sendLog(LOG_DEBUG, "Loop time: " + String(loopTime) + "ms");
Command-Based Configuration
int sensorInterval = 3000;
bool verboseMode = false;
bluetoothMonitor.onMonitorMessage([](const String& message) {
String cmd = message;
cmd.toUpperCase();
if (cmd.startsWith("SET INTERVAL ")) {
sensorInterval = cmd.substring(13).toInt() * 1000;
bluetoothMonitor.send("Interval set to " + String(sensorInterval / 1000) + "s");
} else if (cmd == "VERBOSE ON") {
verboseMode = true;
bluetoothMonitor.send("Verbose mode enabled");
} else if (cmd == "VERBOSE OFF") {
verboseMode = false;
bluetoothMonitor.send("Verbose mode disabled");
} else if (cmd == "CONFIG") {
bluetoothMonitor.send("Interval: " + String(sensorInterval / 1000) + "s");
bluetoothMonitor.send("Verbose: " + String(verboseMode ? "ON" : "OFF"));
}
});
Hardware Integration Examples
Watchdog Monitor
unsigned long lastLoopTime = 0;
unsigned long maxLoopTime = 0;
int warningCount = 0;
void loop() {
unsigned long loopStart = millis();
bluetoothServer.loop();
// Your application code here
performTasks();
unsigned long loopTime = millis() - loopStart;
if (loopTime > maxLoopTime) {
maxLoopTime = loopTime;
}
if (loopTime > 100) { // Warn if loop takes >100ms
warningCount++;
if (bluetooth.isConnected()) {
bluetoothMonitor.send("[WARN] Slow loop: " + String(loopTime) + "ms");
}
}
delay(10);
}
BLE vs Classic Bluetooth - Which to Choose?
| Feature | BLE (Esp32BLE_Monitor) | Classic Bluetooth (Esp32Bluetooth_Monitor) |
|---|---|---|
| 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 monitor
- Check Bluetooth connection status in the app
- Verify connection in Serial Monitor
- Ensure messages are being sent with bluetoothMonitor.send()
- Try disconnecting and reconnecting
3. Commands not being received
- Verify the onMonitorMessage() callback is set up correctly
- Check Serial Monitor for received commands
- Ensure the monitor 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
- Reduce message frequency if sending too fast
5. Messages appear garbled or truncated
- Keep individual messages short (under 200 characters)
- Add small delays between rapid sends
- Check free heap memory for buffer issues
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 debugMonitorStatus() {
Serial.println("=== Monitor Debug ===");
Serial.println("Connected: " + String(bluetooth.isConnected()));
Serial.println("Messages sent: " + String(messageCount));
Serial.println("Free Heap: " + String(ESP.getFreeHeap()));
Serial.println("=====================");
}
Project Ideas
Debugging Projects
- Wireless serial monitor replacement
- Remote sensor data viewer
- Real-time variable inspection
- System performance monitoring
Monitoring Projects
- Weather station data display
- Home automation system status
- Industrial sensor monitoring
- IoT device health dashboard
Logging Projects
- Event logger with timestamps
- Sensor data recording
- Error tracking and alerting
- Performance profiling
Education Projects
- Learn Bluetooth communication
- Practice serial-like messaging
- Understand embedded system monitoring
- Build custom debugging tools
Integration with Other Bluetooth Apps
Combine with Bluetooth Chat
Use Monitor for continuous output and Chat for interactive commands:
// Monitor streams sensor data automatically
void loop() {
if (bluetooth.isConnected() && millis() - lastUpdate >= 3000) {
bluetoothMonitor.send("[SENSOR] " + String(readSensor()));
}
}
// Chat handles interactive commands
bluetoothChat.onChatMessage([](const String& message) {
if (message == "read") {
bluetoothChat.send("Value: " + String(readSensor()));
}
});
Combine with Bluetooth Slider
Use Monitor to display slider values in real time:
bluetoothSlider.onSliderValue([](int slider1, int slider2) {
bluetoothMonitor.send("Slider1=" + String(slider1) + "% Slider2=" + String(slider2) + "%");
bluetoothMonitor.send("PWM1=" + String(map(slider1, 0, 100, 0, 255)) +
" PWM2=" + String(map(slider2, 0, 100, 0, 255)));
});
Next Steps
After mastering the Bluetooth Monitor example, try:
- Bluetooth Chat - For two-way interactive messaging
- Bluetooth Table - For structured data display
- Bluetooth Plotter - For graphical data visualization
- Multiple Bluetooth Apps - Combining monitor with other controls
Support
For additional help:
- Check the API Reference documentation
- Visit DIYables tutorials
- Arduino community forums