Interfacing 8051 with ds1307

[sanpai]

Hello All,

I'm interfacing DS1307 RTC with 8051 using proteus simulator , I have written the code and the seconds part is working fine but the hour and minutes are showing as 0 and is not getting updated . I believe there's some timing issue or the DS1307 register is not getting updated with hour and minute values . I have attached the proteus file,screenshot of the setup and the code here .

Please let me know where i'm going wrong .

#include <reg51.h>

#define lcddata P1
sbit SDA= P0^0;
sbit SCL= P0^1;
sbit RS = P2^0;
sbit RW = P2^1;
sbit EN = P2^2;
sbit BSY = P1^7;


static void I2CInit()
{
  SDA = 1;
  SCL = 1;
}

//I2c start

static void I2CStart()
{
 SCL = 1;
 SDA = 0;
 SCL = 0;
}

static void I2CStop()
{
 SDA = 0;
 SCL = 1;
 SDA = 1;
}

static void I2CAck()
{
 SDA = 0;
 SCL = 1;
 SCL = 0;
}

static void I2CNak()
{
SDA = 1;
SCL = 1;
SCL = 0;
}

static void I2CRestart(){
SDA = 1;
SCL = 1;
SDA = 0;
}

/* routine to send data on the bus */
static unsigned char I2CSend(unsigned char Data)
{
	 unsigned char i, ack_bit;
	 for(i=0;i<8;i++)
	 {
	       SCL = 0;
		   if ((Data & 0x80) == 0)
	       SDA = 0;
		   else
	       SDA = 1;

	       SCL = 1;
	       Data<<=1;
	 }

     SCL = 0;
     ack_bit = SDA;
     SCL = 1;
     SCL = 0;
	 return !ack_bit;
}

/* routine to read the data out of the bus */

static unsigned char I2CRead()
{
	unsigned char i, Data=0;
	for(i=0;i<8;i++)
	{
   	    SCL = 0;
	    SCL = 1;
		if(SDA)
		Data |=1;
		if(i<7)
	    Data<<=1;
	}
   SCL = 0;
   SDA = 1;
	return Data;
}

static void delay(unsigned int);



static void lcd_ready()
{
 //make BSY pin as input 
  BSY=1;
  //Read out from register 
  RS=0;
  //Read
  RW=1;
  while(BSY==1)
  {
    EN=0;
	delay(1);
	EN=1;

  }
}
 
// delay function 
static void delay(unsigned int tme)
{
   unsigned int i,j;
   for(i=0;i<tme;i++)
   for(j=0;j<1275;j++);
}

/* code for sending command to the lcd */

static void lcd_cmd(unsigned char val)
{
  //check for busy flag 
  lcd_ready();
  lcddata=val;
  RS=0;
  RW=0;
  EN=1;
  delay(2);
  EN=0;
}

static void lcd_init()
{
  //16x2 lcd
  lcd_cmd(0x38);
  //clear lcd 
  lcd_cmd(0x01);
  //force the cursor to line 1 
  lcd_cmd(0x80);
   //display on cursor blinking 

   lcd_cmd(0x0E);
}

/* fucntion for transmitting data to the lcd */  
static void lcd_data(unsigned char datum)
{

	  lcd_ready();
	  lcddata=datum;
	  RS=1;
	  RW=0;
	  EN=1;
	  delay(1);
	  EN=0;
 
}

/* code for BCD to ASCII */
static void bcdconv(unsigned char datum)
{
  unsigned char x=0,y=0;
  x=datum&0x0f;
  x=x|0x30;
  y=datum&0xf0;
  y=y>>4;
  y=y|0x30;
  lcd_data(y);
  lcd_data(x);

}


/* main code */
void main()
{

   unsigned char i, a[7];
   unsigned int j;
   I2CInit();
   lcd_init();

/* Writing on i2c */
   I2CStart();
   I2CSend(0xD0);
  
/* first register */

   I2CSend(0x00);

/* seconds  */  
   I2CSend(0x59);
  
/* minutes */
   I2CSend(0x23);
 
/*12-hour mode : need to tick from 3:23 PM */

   I2CSend(0x63);
  
   I2CStop();
   
   while(1)
   {

			I2CStart();
			I2CSend(0xD0);
			I2CSend(0x00);
			/* Actual read */
			I2CRestart();
			I2CSend(0xD1);
			for(i=0;i<3;i++)
			{
			    
				a[i]=I2CRead();
				
				if(i==2)
				I2CNak();
				else
				I2CAck();
			}
			I2CStop();		 
			lcd_cmd(0x81);
			bcdconv(a[2]);
			lcd_data(':');
			bcdconv(a[1]);
			lcd_data(':');
			bcdconv(a[0]);
			for(j=65535;j>0;j--);

   }
    
}

 

[milan.rajik]

Have you written hours and minutes values to RTC? Initial value will be 0. Have you connected 3V battery to RTC's VBAT pin?

 

[sanpai]

Milan

I have attached the proteus binary and the screenshot in the question . I'm grounding the DS1307 battery pin as i'm not using the battery .It was told to be done this way in the datasheet of DS1307 .

As seen in the screenshot only the seconds value is ticking perfectly but the hour and minutes is showing as 0.

 

[milan.rajik]

Battery is needed to hold the set time. If you don't use battery then every time you have to set the time else it will start from 00:00:00. Initially if the RTC was not set to a different value and if there is no battery then you will get this problem. Put battery and set hh:mm to say 2:45 then read RTC and it will display 2:45:00 and if you stop MCU at 2:45 and start it at 2:47 then RTC will show 2:47 as it will be running with the battery even if MCU was off.

Edit: Link for working project. https://saeedsolutions.blogspot.in/2012/11/interfacing-of-8051-with-ds1307-rtc.html

 

[sanpai]

Sorry for replying lately,

There was an issue with the timing of the I2c routines due to which the issue used to occur .

I have written the below code , which works perfectly on the microcontroller .

https://pastebin.com/63UWVdmY

Thanks for the help .