#include <RTClib.h>
#include <Wire.h>
#include <avr/interrupt.h>
#include <avr/sleep.h>
#include <avr/wdt.h>
#include <avr/power.h>

RTC_DS3231 rtc;

// the pin that is connected to SQW
#define CLOCK_INTERRUPT_PIN 2

void setup() {
  wdt_disable();
  sleep_disable();
  delay(100);
  Serial.begin(38400);
  Serial1.begin(38400);
  Serial2.begin(9600);
  Serial3.begin(9600);
  pinMode(13, OUTPUT);// led "L"
  digitalWrite(13, LOW);
  digitalWrite(31, HIGH);//Resert i2c
  pinMode(31, OUTPUT);
  Wire.begin();
  //I21C multiplexer to RTC
  Wire.beginTransmission(0x70);
  Wire.write(1 << 0);  // send byte to selected bus
  Wire.endTransmission();
  delay(100);
  // initializing the rtc
  if(!rtc.begin()) {
    Serial.println("Couldn't find RTC!");
    Serial.flush();
    while (1) delay(10);
  }
  Serial.println("RTC OK");
  rtc.disable32K();
  rtc.clearAlarm(1);
  rtc.clearAlarm(2);
  rtc.writeSqwPinMode(DS3231_OFF);
  rtc.disableAlarm(2);
  pinMode(CLOCK_INTERRUPT_PIN, INPUT_PULLUP);
  wdt_reset();
}

void loop() {
  if(SetNextWakeup()){   
    delay(100);
    wdt_disable();
    deepSleep();
    // after wakeup
    WakeUp();
  }
  else {
    Wire.beginTransmission(0x70);
    Wire.write(1 << 0);  // send byte to selected bus
    Wire.endTransmission();
    delay(1000);
  }
  wdt_reset();
}

void onAlarm() {
  attachInterrupt(digitalPinToInterrupt(CLOCK_INTERRUPT_PIN), onAlarm, FALLING);
  detachInterrupt(CLOCK_INTERRUPT_PIN);
  Serial.begin(38400);
  Serial1.begin(38400);
  Serial2.begin(9600);
  Serial3.begin(9600);
  delay(1000);
  Serial.println("Alarm occured!");
}

bool SetNextWakeup() {
  DateTime now = rtc.now();
  rtc.clearAlarm(1);
  Serial.println("Alarm cleared");
  if(!rtc.setAlarm1(now.unixtime() + 10,DS3231_A1_Date)) {
    Serial.println("Error, alarm wasn't set!");
    return false;
  }
  else {
    Serial.println("Next Alarm will happen in 10 sec!");
    attachInterrupt(digitalPinToInterrupt(CLOCK_INTERRUPT_PIN), onAlarm, LOW);
    return true;
  }
}

void deepSleep(){
  char date[] = {"DD-MM-YYYY hh:mm:ss"};
  rtc.now().toString(date);
  Serial.println(date);

  // the stored alarm value
  DateTime alarm1 = rtc.getAlarm1();
  Ds3231Alarm1Mode alarm1mode = rtc.getAlarm1Mode();
  char alarm1Date[] = {"DD hh:mm:ss"};
  alarm1.toString(alarm1Date);
  Serial.print("Alarm1: ");
  Serial.println(alarm1Date);
    
  Serial.println("setting Arduino's params for the sleep mode");
  set_sleep_mode(SLEEP_MODE_PWR_DOWN);
  sleep_enable();
  delay(100);

  Serial.println("next line will put Arduino in sleep mode");
  digitalWrite(13, LOW);//LED "L"
  Serial.end();
  Serial1.end();
  Serial2.end();
  Serial3.end();
  delay(100);
  sleep_mode();
}

void WakeUp(){ 
  sleep_disable();
  detachInterrupt(CLOCK_INTERRUPT_PIN);
  delay(100);
  //power_all_enable();
  wdt_reset(); 
  MCUSR &= ~(1<<WDRF);
  wdt_enable(WDTO_4S);
  digitalWrite(31, LOW);//Reset multiplexer i2c
  delay(500);
  digitalWrite(31, HIGH);//Enadle multiplexer i2c
  Wire.beginTransmission(0x70);
  Wire.write(1 << 0);  // send byte to selected bus
  Wire.endTransmission();
  delay(100);
  digitalWrite(13, HIGH);//LED "L"
  Serial.println("Wake Up");
  Serial.println("sleep disabled for 5s");
  delay(5000);
}