ESP32 BLE Distance Monitor with Audio Feedback

Documentation

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1. Overview

This firmware enables an ESP32 to:

• 📶 Measure distance using WiFi RSSI (Received Signal Strength Indicator)
• 📱 Communicate via Bluetooth Low Energy (BLE)
• 🔊 Provide audio feedback through a passive buzzer
• 🔄 Reconnect to WiFi automatically if disconnected

Key Features:

• BLE Notifications for distance data
• Melody playback when triggered (iScreech flag)
• WiFi-based distance estimation

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2. Hardware Requirements

• ESP32 (Tested on ESP32-WROOM-32)
• Passive Buzzer (Connected to GPIO 25)
• WiFi Network (For RSSI-based distance measurement)

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3. Software Architecture

3.1 Libraries Used

Library	Purpose
BLEDevice.h	BLE Core Functions
BLEServer.h	BLE Server Setup
BLEUtils.h	BLE Utilities
BLE2902.h	BLE Notifications
WiFi.h	WiFi Connectivity
esp_pm.h	Power Management

3.2 BLE Configuration

UUID	Type	Purpose
0000abcd-...	Service	Main BLE Service
0000deaf-...	TX Characteristic	Sends distance data
0000beef-...	RX Characteristic	Receives commands

• TX Characteristic:

  • Properties: READ + NOTIFY
  • Callback: MyReadingCallBack (sends distance value)

• RX Characteristic:

  • Properties: WRITE
  • Callback: MyCallbacks (triggers buzzer on iScreech)

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4. Key Functions

4.1 setup()

Initializes:

• Serial Monitor (115200 baud)
• Buzzer (GPIO 25)
• BLE (Server, Service, Characteristics)
• WiFi (Connects to ssid and password)

4.2 loop()

1. Measures distance (calculateMediumDistance())
2. Updates BLE (Sends distance via pTxCharacteristic)
3. Plays melody if iScreech == true
4. Reconnects WiFi if disconnected

4.3 Distance Measurement

Function: calculateMediumDistance()

• Uses WiFi RSSI to estimate distance
• Applies log-distance path loss model:

  distance = 10^((txPower - RSSI) / (10 * n))

• Parameters:
  • txPower = -47 (RSSI at 1 meter)
  • n = 2.0 (Path-loss exponent)
• Averages 100 samples for stability

4.4 Buzzer Control

Function: playMelody()

• Plays a 4-note melody (C4, G4, A4, F4)
• Uses tone() and noTone() for clean playback

4.5 BLE Callbacks

Callback	Trigger	Action
onWrite()	Data received	Toggles iScreech if 5 bytes sent
onRead()	Read request	Sends distMedium (2 decimal places)

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5. Usage Instructions

5.1 Flashing the ESP32

1. Install Arduino IDE + ESP32 Core
2. Upload the code
3. Monitor Serial Output (115200 baud)

5.2 BLE Interaction

• Read Distance: Read TX Characteristic (UUID: 0000deaf...)
• Trigger Buzzer: Write 5 bytes to RX Characteristic (UUID: 0000beef...)

5.3 WiFi Setup

Modify in code:

const char* ssid = "qrp";         // Your WiFi SSID
const char* password = "procoder31";  // Your WiFi password

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6. Troubleshooting

Issue	Solution
No BLE Connection	Check UUIDs match in BLE client
Buzzer Not Working	Verify GPIO 25 connection
WiFi Disconnects	Ensure stable network
Inaccurate Distance	Calibrate txPower and n

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7. Customization

7.1 Change Melody

Modify playMelody():

int melody[] = {NOTE_C4, NOTE_E4, NOTE_G4}; // New notes
int durations[] = {300, 300, 300};          // New durations

7.2 Improve Distance Accuracy

• Use BLE RSSI instead of WiFi (replace WiFi.RSSI() with BLE RSSI)
• Implement Kalman Filter for smoothing

ESP32 BLE Distance Monitor - Flutter Client

📱 Overview

This Flutter app connects to an ESP32 over Bluetooth Low Energy (BLE) to:

• 🔍 Scan and connect to an ESP32 running the companion firmware
• 📏 Read distance measurements from the ESP32
• 📲 Send commands to trigger audio feedback on the ESP32

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🛠️ Features

✅ BLE Scanning - Discover nearby ESP32 devices
✅ Distance Monitoring - Read real-time distance values
✅ Command Control - Send "blink" command to ESP32
✅ Auto-Reconnect - Handles connection drops gracefully

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📋 Requirements

• Flutter SDK (v3.0+)
• flutter_blue_plus (BLE plugin)
• ESP32 Firmware (See companion code)
• Android/iOS Device (with BLE support)

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🔌 BLE Configuration

UUID	Type	Purpose
0000abcd-...	Service	Main BLE service
0000deaf-...	TX Characteristic	Receives distance data
0000beef-...	RX Characteristic	Accepts commands

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🚀 Setup

1. Clone the Repository

   git clone https://github.com/your-repo/esp32_ble_flutter.git
   cd esp32_ble_flutter

2. Install Dependencies

   flutter pub get

3. Run on Device

   flutter run

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🎛️ Usage

1. Scanning for Devices

• Tap "Scan for Devices" to discover nearby ESP32s.
• Devices appear in a list below.

2. Connecting to ESP32

• Tap a device to connect.
• The app will:
  • Send a "blink" command (triggers buzzer on ESP32).
  • Enable notifications for distance updates.

3. Reading Distance

• Distance values appear in a Card widget at the bottom.
• Updates automatically via BLE notifications.

4. Debugging

• Connection status appears at the top.
• Errors are logged in the status bar.

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⚙️ Key Functions

Function	Purpose
_startScan()	Starts BLE device discovery
_connectToDevice()	Handles BLE connection logic
_sendMamaliga()	Sends "blink" command
_getDistData()	Reads distance value

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⚠️ Troubleshooting

Issue	Solution
No devices found	Ensure ESP32 is advertising
Connection fails	Check UUIDs match ESP32 firmware
Distance not updating	Verify notifications are enabled

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🔗 Companion ESP32 Code:
ESP32 BLE Distance Monitor Firmware

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8. License

MIT License - Free for personal/commercial use.

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