Bluetooth Low Energy (BLE)

BLE Server and Client

• Broadcast mode: the server transmits data to many clients that are connected
• Mesh network: all the devices are connected, this is a many to many connections

kita bisa melakukan simulasi dengan code sederhana yang telah disediakan oleh software Arduino seperti : 

BLE Server :

#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("MyESP32");

  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();

  pAdvertising->start();

  Serial.println("Characteristic defined! Now you can read it in your phone!");

}

void loop() {

  // put your main code here, to run repeatedly:

  delay(2000);

}

BLE Client :

#include "BLEDevice.h"

//#include "BLEScan.h"

// The remote service we wish to connect to.

static BLEUUID serviceUUID("91bad492-b950-4226-aa2b-4ede9fa42f59");

// The characteristic of the remote service we are interested in.

static BLEUUID    charUUID("0d563a58-196a-48ce-ace2-dfec78acc814");

static BLEAddress *pServerAddress;

static boolean doConnect = false;

static boolean connected = false;

static BLERemoteCharacteristic* pRemoteCharacteristic;

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);

}

bool connectToServer(BLEAddress pAddress) {

    Serial.print("Forming a connection to ");

    Serial.println(pAddress.toString().c_str());

    

    BLEClient*  pClient  = BLEDevice::createClient();

    Serial.println(" - Created client");

    // Connect to the remove BLE Server.

    pClient->connect(pAddress);

    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());

      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());

      return false;

    }

    Serial.println(" - Found our characteristic");

    // Read the value of the characteristic.

    std::string value = pRemoteCharacteristic->readValue();

    Serial.print("The characteristic value was: ");

    Serial.println(value.c_str());

    pRemoteCharacteristic->registerForNotify(notifyCallback);

}

/**

 * 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.getServiceUUID().equals(serviceUUID)) {

      // 

      Serial.print("Found our device!  address: "); 

      advertisedDevice.getScan()->stop();

      pServerAddress = new BLEAddress(advertisedDevice.getAddress());

      doConnect = true;

    } // Found our server

  } // onResult

}; // MyAdvertisedDeviceCallbacks

void setup() {

  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 30 seconds.

  BLEScan* pBLEScan = BLEDevice::getScan();

  pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());

  pBLEScan->setActiveScan(true);

  pBLEScan->start(30);

} // 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(*pServerAddress)) {

      Serial.println("We are now connected to the BLE Server.");

      connected = true;

    } 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) {

    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());

  }

  

  delay(1000); // Delay a second between loops.

} // End of loop

untuk menampilkan informasi yang dikirim dapat dilihat dari smartphone dengan mengunduh aplikasi nRF Connect

Adapun contoh project yang menggunakan komunikasi BLE yaitu 

"pendeteksi gerakan dengan menggunakan sensor PIR"

Code : 

#define timeSeconds 10

// Set GPIOs for LED and PIR Motion Sensor

const int led = 26;

const int motionSensor = 27;

// Timer: Auxiliary variables

unsigned long now = millis();

unsigned long lastTrigger = 0;

boolean startTimer = false;

// Checks if motion was detected, sets LED HIGH and starts a timer

void IRAM_ATTR detectsMovement() {

  Serial.println("MOTION DETECTED!!!");

  digitalWrite(led, HIGH);

  startTimer = true;

  lastTrigger = millis();

}

void setup() {

  // Serial port for debugging purposes

  Serial.begin(115200);

  

  // PIR Motion Sensor mode INPUT_PULLUP

  pinMode(motionSensor, INPUT_PULLUP);

  // Set motionSensor pin as interrupt, assign interrupt function and set RISING mode

  attachInterrupt(digitalPinToInterrupt(motionSensor), detectsMovement, RISING);

  // Set LED to LOW

  pinMode(led, OUTPUT);

  digitalWrite(led, LOW);

}

void loop() {

  // Current time

  now = millis();

  // Turn off the LED after the number of seconds defined in the timeSeconds variable

  if(startTimer && (now - lastTrigger > (timeSeconds*1000))) {

    Serial.println("Motion stopped...");

    digitalWrite(led, LOW);

    startTimer = false;

  }

}