#include <BLE.h>

    char char1Value = 0;
    int char2Value = 0;
    long char3Value = 0;
    String char4Value = String("Hello, world!");

    BLE_Char char1 =
    {
      {0xF1, 0xFF},
      BLE_READABLE | BLE_WRITABLE,
      "Characteristic 1"
    };

    BLE_Char char2 =
    {
      {0xF2, 0xFF},
      BLE_READABLE,
      "Characteristic 2"
    };

    BLE_Char char3 =
    {
      {0xF3, 0xFF},
      BLE_WRITABLE,
      "Characteristic 3"
    };

    BLE_Char char4 =
    {
      {0xF4, 0xFF},
      BLE_NOTIFIABLE,
      "Characteristic 4"
    };

    BLE_Char *simpleServiceChars[] = {&char1, &char2, &char3, &char4};

    BLE_Service simpleService =
    {
      {0xF0, 0xFF},
      4, simpleServiceChars
    };

    void setup() {
      ble.begin();
      ble.addService(&simpleService);
      ble.writeValue(&char1, char1Value);
      ble.writeValue(&char2, char2Value);
      ble.writeValue(&char3, char3Value);
      ble.writeValue(&char4, char4Value);
      ble.setAdvertName("Simple Profile");
      ble.startAdvert();
    }

    void loop() {
      ble.handleEvents();
      // Increment the value of characteristic 1 every second
      if (millis() % 1000 == 0)
      {
        char1Value++;
        ble.writeValue(&char1, char1Value);
      }
    }