Chapter 13 Bluetooth

This chapter mainly introduces how to make simple data transmission through Bluetooth of ESP32-S3 WROOM and mobile phones.

Project 13.1 Bluetooth Low Energy Data Passthrough

Component List

  • ESP32-S3-WROOM x1

  • Type C USB Cable x1

Connect

../_images/connect1.png

Sketch

nRF Connect

In this class, we will use the nRF Connect software for Bluetooth debugging.

Android users can download it from this link: nRF Connect for Android

iPhone users can download it from this link: nRF Connect for iPhone

../_images/ble_software.png

Step1. Upload the code of Project 13.1 to ESP32-S3. Step2. Click on serial monitor.

../_images/20.1.png

Step3. Set baud rate to 115200.

../_images/20.1-1.png

Turn ON Bluetooth on your phone, and open the nrf-connect-for-mobile APP.

../_images/nrf_logo.png

In the Scan page, swipe down to refresh the name of Bluetooth that the phone searches for. Click ESP32S3_Bluetooth.

../_images/20.1-2.jpg ../_images/20.1-3.jpg

Click on the multiple arrow next to the TX Characteristic and make sure it’s off.

../_images/20.1-3.jpg

Back to the serial monitor on your computer. You can type anything in the left border of Send, and then click Send.

../_images/20.11.png

And then you can see the mobile Bluetooth has received the message.

../_images/20.1-4.jpg

Similarly, you can select “Send” on your phone. Set Data format, and then enter anything in the sending box and click Write to send.

../_images/20.1-5.jpg ../_images/20.1-6.jpg

And the computer will receive the message from the mobile Bluetooth.

../_images/20.1-7.png

And now data can be transferred between your mobile phone and computer via ESP32-S3 WROOM.

Code

The following is the program code:

#include "BLEDevice.h"
#include "BLEServer.h"
#include "BLEUtils.h"
#include "BLE2902.h"

BLECharacteristic *pCharacteristic;
bool deviceConnected = false;
uint8_t txValue = 0;
long lastMsg = 0;
String rxload="Test\n";

// Define UUIDs for the BLE service and characteristics
#define SERVICE_UUID           "6E400001-B5A3-F393-E0A9-E50E24DCCA9E"
#define CHARACTERISTIC_UUID_RX "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"
#define CHARACTERISTIC_UUID_TX "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"

// Callback class for BLE server events
class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {
    deviceConnected = true;
    };
    void onDisconnect(BLEServer* pServer) {
    deviceConnected = false;
    }
};

// Callback class for BLE characteristic events
class MyCallbacks: public BLECharacteristicCallbacks {
    void onWrite(BLECharacteristic *pCharacteristic) {
    String rxValue = pCharacteristic->getValue();
    if (rxValue.length() > 0) {
        rxload="";
        for (int i = 0; i < rxValue.length(); i++){
        rxload +=(char)rxValue[i];
        }
    }
    }
};

// Function to set up BLE
void setupBLE(String BLEName){
const char *ble_name=BLEName.c_str();
BLEDevice::init(ble_name);
BLEServer *pServer = BLEDevice::createServer();
pServer->setCallbacks(new MyServerCallbacks());
BLEService *pService = pServer->createService(SERVICE_UUID);
pCharacteristic= pService->createCharacteristic(CHARACTERISTIC_UUID_TX,BLECharacteristic::PROPERTY_NOTIFY);
pCharacteristic->addDescriptor(new BLE2902());
BLECharacteristic *pCharacteristic = pService->createCharacteristic(CHARACTERISTIC_UUID_RX,BLECharacteristic::PROPERTY_WRITE);
pCharacteristic->setCallbacks(new MyCallbacks());
pService->start();
pServer->getAdvertising()->start();
Serial.println("Waiting a client connection to notify...");
}

void setup() {
Serial.begin(115200);
setupBLE("ESP32S3_Bluetooth");
}

void loop() {
long now = millis();
if (now - lastMsg > 100) {
    if (deviceConnected&&rxload.length()>0) {
        Serial.println(rxload);
        rxload="";
    }
    if(Serial.available()>0){
        String str=Serial.readString();
        const char *newValue=str.c_str();
        pCharacteristic->setValue(newValue);
        pCharacteristic->notify();
    }
    lastMsg = now;
}
}

Project 13.2 Bluetooth Control LED

In this section, we will control the LED with Bluetooth.

Component List

  • ESP32-S3-WROOM x1

  • GPIO Extension Board x1

  • 830 Tie-Points Breadboard x1

  • Resistor 220Ω x1

  • LED x1

  • Jumper Wire x2

  • Type C USB Cable x1

Connect

../_images/1.png

Sketch

Sketch_13.2_Bluetooth_Control_LED

../_images/20.2.png

Compile and upload code to ESP32S3_Blueooth. The operation of the APP is the sam e as 27.1, you only need to change the sending content to “led_on” and “led_off” to operate LEDs on the ESP32-S3 WROOM. Data sent from mobile APP:

../_images/20.2-1.jpg

Display on the serial port of the computer:

../_images/20.21.png

When “led_on” is sent, the LED will light up; when “led_off” is sent, the LED will turn off.

Attention: If the sending content isn’t “led-on’ or “led-off”, then the state of LED will not change. If the LED is on, when receiving irrelevant content, it keeps on; Correspondingly, if the LED is off, when receiving irrelevant content, it keeps off

Code

The following is the program code:

#include "BLEDevice.h"
#include "BLEServer.h"
#include "BLEUtils.h"
#include "BLE2902.h"
#include "String.h"

BLECharacteristic *pCharacteristic;
bool deviceConnected = false;
uint8_t txValue = 0;
long lastMsg = 0;
char rxload[20];

// Define UUIDs for the BLE service and characteristics
#define SERVICE_UUID "6E400001-B5A3-F393-E0A9-E50E24DCCA9E"
#define CHARACTERISTIC_UUID_RX "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"
#define CHARACTERISTIC_UUID_TX "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"
#define LED 2  // Define LED pin

// Callback class for BLE server events
class MyServerCallbacks : public BLEServerCallbacks {
void onConnect(BLEServer *pServer) {
    deviceConnected = true;
};
void onDisconnect(BLEServer *pServer) {
    deviceConnected = false;
}
};

// Callback class for BLE characteristic events
class MyCallbacks : public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic *pCharacteristic) {
    String rxValue = pCharacteristic->getValue();
    if (rxValue.length() > 0) {
    for (int i = 0; i < 20; i++) {
        rxload[i] = 0;
    }
    for (int i = 0; i < rxValue.length(); i++) {
        rxload[i] = (char)rxValue[i];
    }
    }
}
};

// Function to set up BLE
void setupBLE(String BLEName) {
const char *ble_name = BLEName.c_str();
BLEDevice::init(ble_name);
BLEServer *pServer = BLEDevice::createServer();
pServer->setCallbacks(new MyServerCallbacks());
BLEService *pService = pServer->createService(SERVICE_UUID);
pCharacteristic = pService->createCharacteristic(CHARACTERISTIC_UUID_TX, BLECharacteristic::PROPERTY_NOTIFY);
pCharacteristic->addDescriptor(new BLE2902());
BLECharacteristic *pCharacteristic = pService->createCharacteristic(CHARACTERISTIC_UUID_RX, BLECharacteristic::PROPERTY_WRITE);
pCharacteristic->setCallbacks(new MyCallbacks());
pService->start();
pServer->getAdvertising()->start();
Serial.println("Waiting a client connection to notify...");
}

void setup() {
pinMode(LED, OUTPUT);  // Set LED pin as output
setupBLE("ESP32S3_Bluetooth");
Serial.begin(115200);
Serial.println("\nThe device started, now you can pair it with Bluetooth!");
}

void loop() {
long now = millis();
if (now - lastMsg > 100) {  // Check every 100ms
    if (deviceConnected && strlen(rxload) > 0) {
    if (strncmp(rxload, "led_on", 6) == 0) {  // If received command is "led_on"
        digitalWrite(LED, HIGH);  // Turn on LED
    }
    if (strncmp(rxload, "led_off", 7) == 0) {  // If received command is "led_off"
        digitalWrite(LED, LOW);  // Turn off LED
    }
    Serial.println(rxload);  // Print received command
    memset(rxload,0,sizeof(rxload));  // Clear rxload buffer
    }
    lastMsg = now;
}
}