ESP32 Project #7: Bluetooth

Hello! On this project I’ll show how Bluetooth Classic and Bluetooth Low Energy work on ESP32. Bluetooth is used for wireless communication in personal area networks (PAN). Bluetooth is a wireless technology that uses low-energy radio waves to send wireless data between Bluetooth-enabled devices. Bluetooth version 4.0 is known as Bluetooth Low Energy or BLE, which remains in sleep mode constantly except for when a connection is initiated.

Bluetooth Classic

Parts and components

  • Breadboard
  • Male to male jumper wires
  • 330 Ohm resistor
  • LED
  • Arduino IDE
  • USB Cable
  • Serial Bluetooth Terminal App

Serial to serial communication

This code is from File > Examples > BluetoothSerial > SerialtoSerialBT.

File > Examples > BluetoothSerial > SerialtoSerialBT
//This example code is in the Public Domain (or CC0 licensed, at your option.)
//By Evandro Copercini - 2018
//
//This example creates a bridge between Serial and Classical Bluetooth (SPP)
//and also demonstrate that SerialBT have the same functionalities of a normal Serial

#include "BluetoothSerial.h"

#if !defined(CONFIG_BT_ENABLED) || !defined(CONFIG_BLUEDROID_ENABLED)
#error Bluetooth is not enabled! Please run `make menuconfig` to and enable it
#endif

BluetoothSerial SerialBT;

void setup() {
Serial.begin(115200);
SerialBT.begin("ESP32test"); //Bluetooth device name
Serial.println("The device started, now you can pair it with bluetooth!");
}

void loop() {
if (Serial.available()) {
SerialBT.write(Serial.read());
}
if (SerialBT.available()) {
Serial.write(SerialBT.read());
}
delay(20);
}

I turned on the bluetooth on my phone and opened the app. Then, I paired the devices by clicking “Devices”. After that, I tried to type and send a message to the serial monitor and this was shown.

Hello

That means the bluetooth worked! Let’s jump to the next trial.

Turn on the LED

Schematics
/*********
Rui Santos
Complete project details at https://randomnerdtutorials.com
*********/
// Load libraries
#include "BluetoothSerial.h"
// Check if Bluetooth configs are enabled
#if !defined(CONFIG_BT_ENABLED) || !defined(CONFIG_BLUEDROID_ENABLED)
#error Bluetooth is not enabled! Please run `make menuconfig` to and enable it
#endif
// Bluetooth Serial object
BluetoothSerial SerialBT;
const int ledPin = 5;
String message = "";
char incomingChar;
String temperatureString = "";
void setup() {
pinMode(ledPin, OUTPUT);
Serial.begin(115200);
// Bluetooth device name
SerialBT.begin("ESP32");
Serial.println("The device started, now you can pair it with bluetooth!");
}
void loop() {
// Read received messages (LED control command)
if (SerialBT.available()){
char incomingChar = SerialBT.read();
if (incomingChar != '\n'){
message += String(incomingChar);
}
else{
message = "";
}
Serial.write(incomingChar);
}
// Check received message and control output accordingly
if (message =="led_on"){
digitalWrite(ledPin, HIGH);
SerialBT.println("LED is on");
}
else if (message =="led_off"){
digitalWrite(ledPin, LOW);
SerialBT.println("LED is off");
}
delay(20);
}
Turn on — turn off

Bluetooth Low Energy

Source is from randomnerdtutorials.

Parts and Components

  • Breadboard
  • nRF Connect for Mobile
  • USB Cable

ESP32 BLE Server

/*
Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleServer.cpp
Ported to Arduino ESP32 by Evandro Copercini
updates by chegewara
*/

#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>

// See the following for generating UUIDs:
// https://www.uuidgenerator.net/

#define SERVICE_UUID "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"

void setup() {
Serial.begin(115200);
Serial.println("Starting BLE work!");

BLEDevice::init("Long name works now");
BLEServer *pServer = BLEDevice::createServer();
BLEService *pService = pServer->createService(SERVICE_UUID);
BLECharacteristic *pCharacteristic = pService->createCharacteristic(
CHARACTERISTIC_UUID,
BLECharacteristic::PROPERTY_READ |
BLECharacteristic::PROPERTY_WRITE
);

pCharacteristic->setValue("Hello World says Neil");
pService->start();
// BLEAdvertising *pAdvertising = pServer->getAdvertising(); // this still is working for backward compatibility
BLEAdvertising *pAdvertising = BLEDevice::getAdvertising();
pAdvertising->addServiceUUID(SERVICE_UUID);
pAdvertising->setScanResponse(true);
pAdvertising->setMinPreferred(0x06); // functions that help with iPhone connections issue
pAdvertising->setMinPreferred(0x12);
BLEDevice::startAdvertising();
Serial.println("Characteristic defined! Now you can read it in your phone!");
}

void loop() {
// put your main code here, to run repeatedly:
delay(2000);
}

ESP32 BLE Scan

/*
Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleScan.cpp
Ported to Arduino ESP32 by Evandro Copercini
*/

#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEScan.h>
#include <BLEAdvertisedDevice.h>

int scanTime = 5; //In seconds
BLEScan* pBLEScan;

class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
void onResult(BLEAdvertisedDevice advertisedDevice) {
Serial.printf("Advertised Device: %s \n", advertisedDevice.toString().c_str());
}
};

void setup() {
Serial.begin(115200);
Serial.println("Scanning...");

BLEDevice::init("");
pBLEScan = BLEDevice::getScan(); //create new scan
pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
pBLEScan->setActiveScan(true); //active scan uses more power, but get results faster
pBLEScan->setInterval(100);
pBLEScan->setWindow(99); // less or equal setInterval value
}

void loop() {
// put your main code here, to run repeatedly:
BLEScanResults foundDevices = pBLEScan->start(scanTime, false);
Serial.print("Devices found: ");
Serial.println(foundDevices.getCount());
Serial.println("Scan done!");
pBLEScan->clearResults(); // delete results fromBLEScan buffer to release memory
delay(2000);
}

Verify and upload. Then open the serial monitor at 115200 baud rate. Don’t forget to press ‘EN’ (enable), and this will show.

Devices found = 1

Testing with Smartphone

I downloaded the app and tried to scan nearby ESP32 device but no devices found. I checked the serial monitor and devices found turned to 0. I don’t know what happened but it changed :)

Final say

Learner || Product and UX enthusiast