/************************************************************************************************* 
                                      PROGRAMMINFO
************************************************************************************************** 
Funktion: Internet Clock mit OLED Display 1,3"
**************************************************************************************************
Version: 17.03.2022
**************************************************************************************************
Board: ESP32vn IoT UNO V1.0.4
**************************************************************************************************
C++ Arduino IDE V1.8.13
**************************************************************************************************
Einstellungen:
https://dl.espressif.com/dl/package_esp32_index.json
http://dan.drown.org/stm32duino/package_STM32duino_index.json
https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_dev_index.json
**************************************************************************************************
Librarys
- WiFi.h V0.16.1
**************************************************************************************************

 **************************************************************************************************/

#include <WiFi.h>
#include <NTPClient.h>
#include <WiFiUdp.h>


const char* ssid     = "xxx";
const char* password = "xxx";


WiFiUDP ntpUDP;
NTPClient timeClient(ntpUDP);

// Variablen
String formattedDate;
String dayStamp;
String timeStamp;

#include <Arduino.h>
#include <U8g2lib.h>

#ifdef U8X8_HAVE_HW_SPI
#include <SPI.h>
#endif
#ifdef U8X8_HAVE_HW_I2C
#include <Wire.h>
#endif

U8G2_SH1106_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, /* reset=*/ U8X8_PIN_NONE);
unsigned long delayTime;

void setup() {

  Serial.begin(115200);
  u8g2.begin();
  
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("");
  Serial.println("WiFi connected.");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());

// NTPClient Zeit
  timeClient.begin();
  // Zeitzonen Offset
  // GMT +1 = 3600
  // GMT +8 = 28800
  // GMT -1 = -3600
  // GMT 0 = 0
  timeClient.setTimeOffset(3600);
}
void loop() {
  while(!timeClient.update()) {
    timeClient.forceUpdate();
  }
  // Eingehendes Format
  // 2018-05-28T16:00:13Z
  // Extrahiere Zeit und Datum
  formattedDate = timeClient.getFormattedDate();
  Serial.println(formattedDate);

  // Extrahiere Datum
  int splitT = formattedDate.indexOf("T");
  dayStamp = formattedDate.substring(0, splitT);
  Serial.print("Datum: ");
  Serial.println(dayStamp);
  // Extrahiere Zeit
  timeStamp = formattedDate.substring(splitT+1, formattedDate.length()-1);
  Serial.print("Uhrzeit: ");
  Serial.println(timeStamp);
  delay(1000);

Serial.println("=================================");
Serial.println("Internet Clock");

    u8g2.setFont(u8g2_font_courR10_tf);
    u8g2.firstPage();

    do {
      
      u8g2.setCursor(1, 10);
      u8g2.print("Internet Clock");
      //u8g2.setCursor(30, 22);
      //u8g2.print("Tegernsee");


u8g2.setFont(u8g2_font_courR14_tf);
      u8g2.setCursor(10, 35);
      u8g2.print(dayStamp);
      u8g2.setCursor(20, 55);
      u8g2.print(timeStamp);


      } while ( u8g2.nextPage() );
     delay(delayTime);
}