update BLE library for ESP32 env compatibility

with the last version of ESP32 arduino env it is not possible to compile on ESP32, we get "missing gatt_api.h" ERROR. So as to avoid that we need to use the last version of the nkolban library for BLE 0.4.16

lib/ESP32_BLE_Arduino/examples/BLE_uart/BLE_uart.ino

@@ -24,8 +24,10 @@
 #include <BLEUtils.h>
 #include <BLE2902.h>
 
-BLECharacteristic *pCharacteristic;
+BLEServer *pServer = NULL;
+BLECharacteristic * pTxCharacteristic;
 bool deviceConnected = false;
+bool oldDeviceConnected = false;
 uint8_t txValue = 0;
 
 // See the following for generating UUIDs:
@@ -70,26 +72,26 @@ void setup() {
   BLEDevice::init("UART Service");
 
   // Create the BLE Server
-  BLEServer *pServer = BLEDevice::createServer();
+  pServer = BLEDevice::createServer();
   pServer->setCallbacks(new MyServerCallbacks());
 
   // Create the BLE Service
   BLEService *pService = pServer->createService(SERVICE_UUID);
 
   // Create a BLE Characteristic
-  pCharacteristic = pService->createCharacteristic(
-                      CHARACTERISTIC_UUID_TX,
-                      BLECharacteristic::PROPERTY_NOTIFY
-                    );
+  pTxCharacteristic = pService->createCharacteristic(
+										CHARACTERISTIC_UUID_TX,
+										BLECharacteristic::PROPERTY_NOTIFY
+									);
                       
-  pCharacteristic->addDescriptor(new BLE2902());
+  pTxCharacteristic->addDescriptor(new BLE2902());
 
-  BLECharacteristic *pCharacteristic = pService->createCharacteristic(
-                                         CHARACTERISTIC_UUID_RX,
-                                         BLECharacteristic::PROPERTY_WRITE
-                                       );
+  BLECharacteristic * pRxCharacteristic = pService->createCharacteristic(
+											 CHARACTERISTIC_UUID_RX,
+											BLECharacteristic::PROPERTY_WRITE
+										);
 
-  pCharacteristic->setCallbacks(new MyCallbacks());
+  pRxCharacteristic->setCallbacks(new MyCallbacks());
 
   // Start the service
   pService->start();
@@ -101,11 +103,23 @@ void setup() {
 
 void loop() {
 
-  if (deviceConnected) {
-    Serial.printf("*** Sent Value: %d ***\n", txValue);
-    pCharacteristic->setValue(&txValue, 1);
-    pCharacteristic->notify();
-    txValue++;
-  }
-  delay(1000);
+    if (deviceConnected) {
+        pTxCharacteristic->setValue(&txValue, 1);
+        pTxCharacteristic->notify();
+        txValue++;
+		delay(10); // bluetooth stack will go into congestion, if too many packets are sent
+	}
+
+    // disconnecting
+    if (!deviceConnected && oldDeviceConnected) {
+        delay(500); // give the bluetooth stack the chance to get things ready
+        pServer->startAdvertising(); // restart advertising
+        Serial.println("start advertising");
+        oldDeviceConnected = deviceConnected;
+    }
+    // connecting
+    if (deviceConnected && !oldDeviceConnected) {
+		// do stuff here on connecting
+        oldDeviceConnected = deviceConnected;
+    }
 }