BLE Client Server menggunakan 2 ESP32

Pada project kali ini akan  mengontrol LED ESP32 berkedip dengan dua buah ESP32 sebagai Client dan Server menggunakan Bluetooth  Low Energy (BLE). Sebelum membuat project ini  siapkan alat-alat yang diperlukan sebagai berikut:

• 2 buah ESP32
• 2 buah Kabel data USB

buka aplikasi Arduino IDE. Apabila belum pernah menginstall dan mengupload program menggunakan Arduino IDE bisa pelajari terlebih dahulu dalam postingan sebelumnya disini.

Selanjutnya pada ESP32 server buka program BLE server, klik file>>examples>> ESP32 BLE Arduino>>BLE_Server. Kemudian muncul program seperti pada gambar 1.2, kemudian upload program tersebut.

Untuk Dapat terhubung antara ESP32 client dan ESP32 server BLE UUID pada kedua ESP32 harus sama. Pada ESP32 Client upload program dibawah ini:

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/**
 * A BLE client example that is rich in capabilities.
 * There is a lot new capabilities implemented.
 * author unknown
 * updated by chegewara
 */

#include "BLEDevice.h"
//#include "BLEScan.h"
int LED = 2;
// The remote service we wish to connect to.
static BLEUUID serviceUUID("4fafc201-1fb5-459e-8fcc-c5c9c331914b");
// The characteristic of the remote service we are interested in.
static BLEUUID charUUID("beb5483e-36e1-4688-b7f5-ea07361b26a8");

static boolean doConnect = false;
static boolean connected = false;
static boolean doScan = false;
static BLERemoteCharacteristic* pRemoteCharacteristic;
static BLEAdvertisedDevice* myDevice;

static void notifyCallback(
BLERemoteCharacteristic* pBLERemoteCharacteristic,
uint8_t* pData,
size_t length,
bool isNotify) {
Serial.print("Notify callback for characteristic ");
Serial.print(pBLERemoteCharacteristic->getUUID().toString().c_str());
Serial.print(" of data length ");
Serial.println(length);
Serial.print("data: ");
Serial.println((char*)pData);
}

class MyClientCallback : public BLEClientCallbacks {
void onConnect(BLEClient* pclient) {
}

void onDisconnect(BLEClient* pclient) {
connected = false;
Serial.println("onDisconnect");
}
};

bool connectToServer() {
Serial.print("Forming a connection to ");
Serial.println(myDevice->getAddress().toString().c_str());

BLEClient* pClient = BLEDevice::createClient();
Serial.println(" - Created client");

pClient->setClientCallbacks(new MyClientCallback());

// Connect to the remove BLE Server.
pClient->connect(myDevice); // if you pass BLEAdvertisedDevice instead of address, it will be recognized type of peer device address (public or private)
Serial.println(" - Connected to server");

// Obtain a reference to the service we are after in the remote BLE server.
BLERemoteService* pRemoteService = pClient->getService(serviceUUID);
if (pRemoteService == nullptr) {
Serial.print("Failed to find our service UUID: ");
Serial.println(serviceUUID.toString().c_str());
pClient->disconnect();
return false;
}
Serial.println(" - Found our service");


// Obtain a reference to the characteristic in the service of the remote BLE server.
pRemoteCharacteristic = pRemoteService->getCharacteristic(charUUID);
if (pRemoteCharacteristic == nullptr) {
Serial.print("Failed to find our characteristic UUID: ");
Serial.println(charUUID.toString().c_str());
pClient->disconnect();
return false;
}
Serial.println(" - Found our characteristic");

// Read the value of the characteristic.
if(pRemoteCharacteristic->canRead()) {
std::string value = pRemoteCharacteristic->readValue();
Serial.print("The characteristic value was: ");
Serial.println(value.c_str());
}

if(pRemoteCharacteristic->canNotify())
pRemoteCharacteristic->registerForNotify(notifyCallback);

connected = true;
}
/**
 * Scan for BLE servers and find the first one that advertises the service we are looking for.
 */
class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
/**
   * Called for each advertising BLE server.
   */
void onResult(BLEAdvertisedDevice advertisedDevice) {
Serial.print("BLE Advertised Device found: ");
Serial.println(advertisedDevice.toString().c_str());

// We have found a device, let us now see if it contains the service we are looking for.
if (advertisedDevice.haveServiceUUID() && advertisedDevice.isAdvertisingService(serviceUUID)) {

BLEDevice::getScan()->stop();
myDevice = new BLEAdvertisedDevice(advertisedDevice);
doConnect = true;
doScan = true;

} // Found our server
} // onResult
}; // MyAdvertisedDeviceCallbacks


void setup() {
pinMode (LED_BUILTIN, OUTPUT);
Serial.begin(115200);
Serial.println("Starting Arduino BLE Client application...");
BLEDevice::init("");

// Retrieve a Scanner and set the callback we want to use to be informed when we
// have detected a new device. Specify that we want active scanning and start the
// scan to run for 5 seconds.
BLEScan* pBLEScan = BLEDevice::getScan();
pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
pBLEScan->setInterval(1349);
pBLEScan->setWindow(449);
pBLEScan->setActiveScan(true);
pBLEScan->start(5, false);
} // End of setup.


// This is the Arduino main loop function.
void loop() {

// If the flag "doConnect" is true then we have scanned for and found the desired
// BLE Server with which we wish to connect. Now we connect to it. Once we are
// connected we set the connected flag to be true.
if (doConnect == true) {
if (connectToServer()) {
Serial.println("We are now connected to the BLE Server.");
} else {
Serial.println("We have failed to connect to the server; there is nothin more we will do.");
}
doConnect = false;
}

// If we are connected to a peer BLE Server, update the characteristic each time we are reached
// with the current time since boot.
if (connected) {
digitalWrite(LED_BUILTIN , HIGH); // turn the LED on (HIGH is the voltage level)
delay(1000);
digitalWrite(LED_BUILTIN, LOW); // turn the LED off by making the voltage LOW
delay(1000); // wait for a second
String newValue = "Time since boot: " + String(millis()/1000);
Serial.println("Setting new characteristic value to \"" + newValue + "\"");

// Set the characteristic's value to be the array of bytes that is actually a string.
pRemoteCharacteristic->writeValue(newValue.c_str(), newValue.length());
}else if(doScan){
BLEDevice::getScan()->start(0); // this is just eample to start scan after disconnect, most likely there is better way to do it in arduino
}
delay(1000); // Delay a second between loops.
} // End of loop

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Tekan tombol enable pada ESP32 Client  kemudian Bluetooth client dan server akan tehubung, setelah Bluetooth terhubung maka LED pada ESP32 client akan berkedip. Apabila Bluetooth ESP32 client dan server tidak terhubung maka LED pada ESP32 client mati.