//This library contains the functions regarding ds3231.In order to function properly,twi core functions library must be included

#include "ds3231.h"

void ds3231_init(void)
{
twi_init();
twi_start();
twi_send(0xD0);//initial address of ds3231+0 to write next byte
twi_send(0x0E);//write location of control resistor
twi_send(0x00);//Enable SQW at 1hz.This is to make atmega sync with DS3231 every second
twi_stop();
}

void ds3231_set(uint8_t hr,uint8_t min,uint8_t sec,uint8_t ampm,uint8_t yr,uint8_t mnth,uint8_t dt,uint8_t day)
{
hr &=0b00011111;//clear first three bits.
hr |=0b01000000;//make D7=0,D6=1 for am/pm view,D5=0 for AM/1 for PM.
hr |=(ampm<<5);

twi_start();
twi_send(0xD0);//initial address of ds3231+0 to write next byte
twi_send(0x00);//select location 0 to update 
twi_send(sec);//update second
twi_send(min);//write location of control resistor
twi_send(hr);//write 0 to the content of the resistor
twi_send(day);//update day of the week
twi_send(dt);//update date
twi_send(mnth);//update month
twi_send(yr);//update year
twi_stop();
}




void ds3231_get(uint8_t *h,uint8_t *m,uint8_t *s,uint8_t *yr,uint8_t *mnth,uint8_t *dt,uint8_t *day)
{
twi_start();
twi_send(0xD0);
twi_send(0x00);

twi_start();
twi_send(0xD1);//ds3231 address+1 to read
*s=twi_receive(1);//1 to send ACK
*m=twi_receive(1);//1 to send ACK
*h=twi_receive(1);//0 to send NACK
*day=twi_receive(1);//1 to send ACK,read day
*dt=twi_receive(1);//1 to send ACK,read date
*mnth=twi_receive(1);//1 to send ACK,read month
*yr=twi_receive(0);//0 to send NACK,read year

twi_stop();
}