Detailed explanation of ds1302 clock program for avr microcontroller

ds1302 is a clock chip and has nothing to do with avr. Here, mega32 is used to operate the chip. There is a lot of information about this chip on the Internet. Let me briefly talk about it. The communication method is SPI mode. There are several registers inside the chip to store year, month, day, hour, minute, and second, and there is write protection, etc.

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//CPU:mega32
//Compiler:iar
//DS1302
//Call LCD display function in main function

#include
#include "lcd.h"
void Write1302 ( unsigned char addr,unsigned char dat );
unsigned char Read1302 ( unsigned char addr );
void ds1302_init(void);

//Register macro definitions
#define SECOND 0x80
#define MINUTE 0x82
#define HOUR 0x84
#define DAY 0x86
#define MONTH 0x88
#define YEAR 0x8C
#define PROTECT 0x8E

//Pin definition
#define CE PORTD_Bit5 //Read and write enable
#define SCLK PORTD_Bit6 //Clock
#define TIO PORTD_Bit7 //Data output
#define RIO PIND_Bit7 //Data input
#define CE_D DDRD_Bit5 //CE direction
#define SCLK_D DDRD_Bit6 //SCLK direction
#define IO_D DDRD_Bit7 //IO direction

void main(void)
{
  ds1302_init();
  lcd_init();
  while(1)
  {
    delay(10000);
    clear();
    display_string(num2str(Read1302(YEAR)),0,0);display_string("YEAR",0,16);display_string(num2str(Read1302(MONTH)),0,64);display_string("MONTH",0,80);
    display_string(num2str(Read1302(DAY)),2,0);display_string("DAY",2,16);display_string(num2str(Read1302(HOUR)),2,64);display_string("HOUR",2,80);
    display_string(num2str(Read1302(MINUTE)),4,0);display_string("MIN",4,16);display_string(num2str(Read1302(SECOND)),4,64);display_string("SECOND",4,80);
  }
}

//Address, data sending subroutine
void Write1302 ( unsigned char addr,unsigned char data )
{
    unsigned char i;
    IO_D = 1;
    CE = 0; //CE pin is low, data transmission is terminated
    SCLK = 0; //Clear clock bus
    CE = 1; //CE pin is high, logic control is valid
    //Send address
    for ( i=8; i>0; i-- ) //Loop 8 times shift
    {
        SCLK = 0;
        TIO = (addr&0x01); //Transmit low byte each time
        addr >>= 1; //Shift right one bit
        SCLK = 1;
    }
    //Send data
    for ( i=8; i>0; i-- )
    {
        SCLK = 0;
        TIO = (data&0x01);
        data >>= 1;
        SCLK = 1;
    }
    
    CE = 0;

}
//Data reading subroutine
unsigned char Read1302 ( unsigned char addr )
{
    unsigned char i,data=0,temp;
    addr = addr | 1;//Change to read address
    IO_D = 1;
    CE=0;
    SCLK=0;
    CE = 1;
    //Send address
    for ( i=8; i>0; i-- ) //Loop 8 times shift
    {
        SCLK = 0;
        TIO = (addr&0x01); //Transmit low byte each time
        addr >>= 1; //Shift right one bit
        SCLK = 1;
    }
    IO_D = 0;
    //Read data
    for ( i=0; i<8; i++ )
    {
        SCLK = 1;
        SCLK = 0;
        data |= RIO<    }
    
    CE=0;
    
  // data = data/16*10 + data&0x0f ; Why not
    temp = data>>4;
    data &= 0x0f;
    data = temp*10 + data;
    
    return (data);
}
//Initialize DS1302
void ds1302_init(void)
{
    CE_D = 1 ; //CE output
    SCLK_D = 1 ; //SCLK output
    Write1302 (PROTECT,0X00); //Disable write protection
    Write1302 (SECOND ,0x30); //Initialize seconds
    Write1302 (MINUTE ,0x05); //Initialize minutes
    Write1302 (HOUR ,0x6); //Initialize hours
    Write1302 (DAY ,0x14); //Initialize days
    Write1302 (MONTH ,0x12); //Initialize months
    Write1302 (YEAR ,0x88); //Initialize years
    Write1302 (PROTECT,0x80); //Enable write protection
}

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