#include "Wire.h"
#define DS3231_ADDRESSE 0x68

int merker1=100;
int merker2=100;
int merker3=100;
int merker4=100;

int tasterminute=15;
int tasterstatusm = 0;
int tasterstunde=16;
int tasterstatush = 0;

void setup() {
Wire.begin();
pinMode(14, OUTPUT);
pinMode(tasterminute, INPUT);
pinMode(tasterstunde, INPUT);
pinMode(2, OUTPUT); pinMode(3, OUTPUT); pinMode(4, OUTPUT); pinMode(5, OUTPUT); pinMode(6, OUTPUT); pinMode(7, OUTPUT);
pinMode(8, OUTPUT); pinMode(9, OUTPUT); pinMode(10, OUTPUT); pinMode(11, OUTPUT); pinMode(12, OUTPUT); pinMode(13, OUTPUT);
digitalWrite(2, LOW); digitalWrite(4, HIGH); digitalWrite(5, LOW); digitalWrite(7, HIGH);
digitalWrite(8, LOW); digitalWrite(10, HIGH); digitalWrite(11, LOW); digitalWrite(13, HIGH);
digitalWrite(2, HIGH); digitalWrite(4, LOW); digitalWrite(5, HIGH); digitalWrite(7, LOW);
digitalWrite(8, HIGH); digitalWrite(10, LOW); digitalWrite(11, HIGH); digitalWrite(13, LOW);
}

void loop() {
  BerlinUhr();
  }

void leseDS3231zeit(byte *sekunde, byte *minute,byte *stunde, byte *wochentag, byte *tag, byte *monat, byte *jahr) {
  Wire.beginTransmission(DS3231_ADDRESSE);
  Wire.write(0); // DS3231 Register zu 00h
  Wire.endTransmission();
  Wire.requestFrom(DS3231_ADDRESSE, 7);
  *sekunde = bcdToDec(Wire.read() & 0x7f);
  *minute = bcdToDec(Wire.read());
  *stunde = bcdToDec(Wire.read() & 0x3f);
  *wochentag = bcdToDec(Wire.read());
  *tag = bcdToDec(Wire.read());
  *monat = bcdToDec(Wire.read());
  *jahr = bcdToDec(Wire.read());
}
void BerlinUhr(){
byte sekunde, minute, stunde, wochentag, tag, monat, jahr;
  leseDS3231zeit(&sekunde, &minute, &stunde, &wochentag, &tag, &monat, &jahr);
if (sekunde %2 == 0)
{
digitalWrite(14, HIGH); 
} else {
digitalWrite(14, LOW); 
}
if (minute != merker1)
{ 
if ((minute == 1) || (minute== 6) || (minute== 11) || (minute== 16) || (minute== 21) || (minute== 26) || (minute== 31) || (minute== 36) || (minute== 41) || (minute== 46) || (minute== 51) || (minute== 56))
{ 
digitalWrite(2, LOW);digitalWrite(2, HIGH);
digitalWrite(3, HIGH); digitalWrite(3, LOW); digitalWrite(4, HIGH); digitalWrite(4, LOW);
}
if ((minute == 2) || (minute== 7) || (minute== 12) || (minute== 17) || (minute== 22) || (minute== 27) || (minute== 32) || (minute== 37) || (minute== 42) || (minute== 47) || (minute== 52) || (minute== 57))
{ 
digitalWrite(2, LOW);digitalWrite(2, HIGH);
digitalWrite(3, HIGH); digitalWrite(3, LOW); digitalWrite(3, HIGH); digitalWrite(3, LOW); digitalWrite(4, HIGH); digitalWrite(4, LOW);
}
if ((minute == 3) || (minute== 8) || (minute== 13) || (minute== 18) || (minute== 23) || (minute== 28) || (minute== 33) || (minute== 38) || (minute== 43) || (minute== 48) || (minute== 53) || (minute== 58))
{ 
digitalWrite(2, LOW);digitalWrite(2, HIGH);
digitalWrite(3, HIGH); digitalWrite(3, LOW); digitalWrite(3, HIGH); digitalWrite(3, LOW); digitalWrite(3, HIGH);digitalWrite(3, LOW); digitalWrite(4, HIGH); digitalWrite(4, LOW);
}
if ((minute == 4) || (minute== 9) || (minute== 14) || (minute== 19) || (minute== 24) || (minute== 29) || (minute== 34) || (minute== 39) || (minute== 44) || (minute== 49) || (minute== 54) || (minute== 59))
{ 
digitalWrite(2, LOW);digitalWrite(2, HIGH);
digitalWrite(3, HIGH); digitalWrite(3, LOW); digitalWrite(3, HIGH); digitalWrite(3, LOW); digitalWrite(3, HIGH);digitalWrite(3, LOW); digitalWrite(3, HIGH); digitalWrite(3, LOW);digitalWrite(4, HIGH); digitalWrite(4, LOW);
}
if ((minute == 0) || (minute== 5)|| (minute== 10) || (minute== 15) || (minute== 20) || (minute== 25) || (minute== 30) || (minute== 35) || (minute== 40) || (minute== 45) || (minute== 50) || (minute== 55))
{ 
digitalWrite(2, LOW);digitalWrite(2, HIGH);
digitalWrite(4, HIGH); digitalWrite(4, LOW);
}
merker1 = minute;
}
if (minute != merker2)
{
if ((minute >=5) and (minute <=9))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=10) and (minute <=14))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=15) and (minute <=19))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=20) and (minute <=24))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=25) and (minute <=29))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);
digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=30) and (minute <=34))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);
digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=35) and (minute <=39))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);
digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=40) and (minute <=44))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);
digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=45) and (minute <=49))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);
digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=50) and (minute <=54))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);
digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);
digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if ((minute >=55) and (minute <=59))
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW); digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);
digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(6, HIGH); digitalWrite(6, LOW);
digitalWrite(6, HIGH); digitalWrite(6, LOW);digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
if (minute ==0)
{
digitalWrite(5, LOW);digitalWrite(5, HIGH);
digitalWrite(7, HIGH); digitalWrite(7, LOW);
}
}
if (stunde != merker3)
{
if ((stunde == 1) || (stunde == 6) || (stunde == 11) || (stunde == 16) || (stunde == 21))
{ 
digitalWrite(8, LOW);digitalWrite(8, HIGH);
digitalWrite(9, HIGH); digitalWrite(9, LOW); digitalWrite(10, HIGH); digitalWrite(10, LOW);
}
if ((stunde == 2) || (stunde == 7) || (stunde == 12) || (stunde == 17) || (stunde == 22))
{ 
digitalWrite(8, LOW);digitalWrite(8, HIGH);
digitalWrite(9, HIGH); digitalWrite(9, LOW);digitalWrite(9, HIGH); digitalWrite(9, LOW); digitalWrite(10, HIGH); digitalWrite(10, LOW);
}
if ((stunde == 3) || (stunde == 8) || (stunde == 13) || (stunde == 18) || (stunde == 23))
{ 
digitalWrite(8, LOW);digitalWrite(8, HIGH);
digitalWrite(9, HIGH); digitalWrite(9, LOW);digitalWrite(9, HIGH);digitalWrite(9, LOW); digitalWrite(9, HIGH);digitalWrite(9, LOW); digitalWrite(10, HIGH); digitalWrite(10, LOW);
}
if ((stunde == 4) || (stunde == 9) || (stunde == 14) || (stunde == 19) || ((stunde == 0) and (minute ==0)))
{ 
digitalWrite(8, LOW);digitalWrite(8, HIGH);
digitalWrite(9, HIGH); digitalWrite(9, LOW);digitalWrite(9, HIGH); digitalWrite(9, LOW);digitalWrite(9, HIGH);digitalWrite(9, LOW); digitalWrite(9, HIGH);digitalWrite(9, LOW); digitalWrite(10, HIGH); digitalWrite(10, LOW);
}
if (((stunde == 0) and (minute >=1)) || (stunde == 5) || (stunde == 10) || (stunde == 15) || (stunde == 20))
{ 
digitalWrite(8, LOW);digitalWrite(8, HIGH);
digitalWrite(10, HIGH); digitalWrite(10, LOW);
}
}
if (stunde != merker4)
{
if ((stunde >=5) and (stunde <=9))
{
digitalWrite(11, LOW);digitalWrite(11, HIGH);
digitalWrite(12, HIGH); digitalWrite(12, LOW); digitalWrite(13, HIGH); digitalWrite(13, LOW);
}
if ((stunde >=10) and (stunde <=14))
{
digitalWrite(11, LOW);digitalWrite(11, HIGH);
digitalWrite(12, HIGH); digitalWrite(12, LOW); digitalWrite(12, HIGH); digitalWrite(12, LOW);digitalWrite(13, HIGH); digitalWrite(13, LOW);
}
if ((stunde >=15) and (stunde <=19))
{
digitalWrite(11, LOW);digitalWrite(11, HIGH);
digitalWrite(12, HIGH); digitalWrite(12, LOW); digitalWrite(12, HIGH); digitalWrite(12, LOW);digitalWrite(12, HIGH); digitalWrite(12, LOW);digitalWrite(13, HIGH); digitalWrite(13, LOW);
}
if (((stunde >=20) and (stunde <=24)) or ((stunde ==0) and (minute ==0)))
{
digitalWrite(11, LOW);digitalWrite(11, HIGH);
digitalWrite(12, HIGH); digitalWrite(12, LOW); digitalWrite(12, HIGH); digitalWrite(12, LOW);digitalWrite(12, HIGH); digitalWrite(12, LOW);digitalWrite(12, HIGH); digitalWrite(12, LOW);digitalWrite(13, HIGH); digitalWrite(13, LOW);
}
if ((stunde == 0) and (minute >=1))
{
digitalWrite(11, LOW);digitalWrite(11, HIGH);
digitalWrite(13, HIGH); digitalWrite(13, LOW);
}
}
tasterstatusm=digitalRead(tasterminute);
if (tasterstatusm == HIGH)
{
minute = minute + 1;
sekunde = 1;
if (minute == 60) minute = 0;
  Wire.beginTransmission(DS3231_ADDRESSE);
  Wire.write(0);
  Wire.write(decToBcd(sekunde));
  Wire.write(decToBcd(minute));
  Wire.write(decToBcd(stunde));
  Wire.write(decToBcd(wochentag));
  Wire.write(decToBcd(tag));
  Wire.write(decToBcd(monat));
  Wire.write(decToBcd(jahr));
  Wire.endTransmission();
  delay (200);
}

tasterstatush=digitalRead(tasterstunde);
if (tasterstatush == HIGH)
{
stunde = stunde + 1;
if (stunde >= 24) stunde = 0;
  Wire.beginTransmission(DS3231_ADDRESSE);
  Wire.write(0);
  Wire.write(decToBcd(sekunde));
  Wire.write(decToBcd(minute));
  Wire.write(decToBcd(stunde));
  Wire.write(decToBcd(wochentag));
  Wire.write(decToBcd(tag));
  Wire.write(decToBcd(monat));
  Wire.write(decToBcd(jahr));
  Wire.endTransmission();
  delay (200);
}
}
byte decToBcd(byte val) {
// Dezimal Zahl zu binary coded decimal (BCD) umwandeln
  return((val/10*16) + (val%10));
}
byte bcdToDec(byte val) {
// BCD (binary coded decimal) in Dezimal Zahl umwandeln
  return((val/16*10) + (val%16));
}