/************************************************************************/
/*									*/
/*			Serial LCD Routines				*/
/*									*/
/*			Test Program: Clock / Calendar			*/
/*                                                                      */
/*              Author: Peter Dannegger                                 */
/*                      danni@specs.de                                  */
/*                                                                      */
/************************************************************************/
#pragma cd pl(9999)

#include <reg2051.h>


sbit	LCD_E	= P1^6;
sbit	LCD_CK	= P1^5;
sbit	LCD_RS	= P1^7;


/* connections:
89C2051		74HCT164	LCD
----------------------------------------
P1.5		8
P1.6				E
P1.7		1, 2		RS
VCC		9, 14		VDD
GND		7		VSS, R/W
		3		D1
		4		D3
		5		D5
		6		D7
		10		D6
		11		D4
		12		D2
		13		D0
*/


#define	XTAL	11.0592e6


#define uchar unsigned char


void	lcd_data( uchar d );
void	lcd_text( uchar *t );
void	lcd_command( uchar d );
void	lcd_init( void );
void	display_clock( void );
void	clock( void );


struct time {
  uchar sec;
  uchar min;
  uchar hour;
  uchar day;
  uchar wday;
  uchar month;
  uchar year;
};


extern struct time data time;
extern bit F_1sec, F_1min, F_1hour;


/************************************************************************/
/*									*/
/*				LCD - Routines				*/
/*									*/
/************************************************************************/

#define	TWAIT	( XTAL / 12 / 512 )

uchar position;


void lcdout( uchar d, bit rs )
{
  uchar code BIT_NO[] = { 0x01, 0x04, 0x10, 0x40, 0x80, 0x20, 0x08, 0x02 };
  uchar i;

  LCD_E = 0;
  for( i = 0; i < 8; i++ ){
    LCD_CK = 0;
    LCD_RS = d & BIT_NO[i];
    LCD_CK = 1;
  }
  LCD_RS = rs;
  LCD_E = 1;
  i = XTAL / 12 / 2 * 46e-6;
  LCD_E = 0;
  while( --i );					// wait 46us
}


void wait512( uchar t )			// Tw = 512 cycle * t
{
  uchar i = 0;

  do
    while( --i );
  while( --t );
}


void lcd_command( uchar d )
{
  lcdout( d, 0 );

  if( d & 0x80 )
    position = d;
  switch( d ){
    case 1:
    case 2:
    case 3: wait512( 2 + TWAIT * 1.6e-3 );	// wait 1.6ms
  }
}


void lcd_data( uchar d )
{
  lcdout( d, 1 );
  position++;
  if( position == 0x90 )
    position = 0xC0;
  else
    if( position == 0xD0 )
      position = 0x80;
    else
      return;
  lcd_command( position );
}


void lcd_init( void )
{
  wait512( 1 + TWAIT * 15e-3 );		// wait 15ms
  lcd_command( 0x30 ),
  wait512( 1 + TWAIT * 4.1e-3 );		// wait 4.1ms
  lcd_command( 0x30 );
  wait512( 1 );
  lcd_command( 0x30 );

  lcd_command( 0x38 );		// 2 lines 5*7
  lcd_command( 0x08 );		// display off
  lcd_command( 0x01 );		// display clear
  lcd_command( 0x06 );
  lcd_command( 0x0C );		// no cursor, no blink
  position = 0x80;
}


/************************************************************************/
/*									*/
/*			Clock / Calendar				*/
/*                                                                      */
/*              Author: Peter Dannegger                                 */
/*                      danni@specs.de                                  */
/*                                                                      */
/************************************************************************/

struct time data time;


void display_clock( void )
{
  lcd_command( 0x80 );				// line 1
  lcd_data( time.hour / 10 + '0');
  lcd_data( time.hour % 10 + '0');
  lcd_data( ':' );
  lcd_data( time.min / 10 + '0');
  lcd_data( time.min % 10 + '0');
  lcd_data( ':' );
  lcd_data( time.sec / 10 + '0');
  lcd_data( time.sec % 10 + '0');

  lcd_command( 0xC0 );				// line 2
  lcd_data( time.day / 10 + '0');
  lcd_data( time.day % 10 + '0');
  lcd_data( '.' );
  lcd_data( time.month / 10 + '0');
  lcd_data( time.month % 10 + '0');
  lcd_data( '.' );
  lcd_data( '2' );
  lcd_data( '0' );
  lcd_data( time.year / 10 + '0');
  lcd_data( time.year % 10 + '0');
}


void clock(void)
{
  uchar code MDAYS[] = {
    30, 32, 29, 32, 31, 32, 31, 32, 32, 31, 32, 31, 32 };
  uchar i;

  time.sec++;
  if( time.sec == 60 ){
    time.sec = 0;
    F_1min = 1;				// to correct deviation per minute
    time.min++;
    if( time.min == 60 ){
      time.min = 0;
      F_1hour = 1;
      time.hour++;
      switch( time.hour ){
	case 24:
	  time.hour = 0;
	  time.day++;
	  time.wday++;
	  if( time.wday == 8 )
	    time.wday = 1;
	  i = time.month;
	  if( i == 2 && (time.year & 3) == 0 )	// leap year
	    i = 0;
	  if( MDAYS[i] == time.day ){
	    time.day = 1;
	    time.month++;
	    if( time.month == 13 ){
	      time.month = 1;
	      time.year++;
	      if( time.year == 100 )
		time.year = 0;			// next century
	    }
	  }
	  break;
//	case 2:
//	case 3: summertime(); break;
      }
    }
  }
}


/************************************************************************/
/*                                                                      */
/*			High Precise Time Base				*/
/*                                                                      */
/*              Author: Peter Dannegger                                 */
/*                      danni@specs.de                                  */
/*                                                                      */
/************************************************************************/

bit F_1sec, F_1min, F_1hour;

#define T_INTERVAL	(XTAL / 12.0 / 16384)
#define PRESC_1S	(uchar)(T_INTERVAL + 0.5)
#define PRESC_1M	(uchar)((T_INTERVAL - PRESC_1S) * 60 + PRESC_1S + 0.5)
#define PRESC_1H	(T_INTERVAL * 60 - PRESC_1S * 59 - PRESC_1M) * 60 + PRESC_1M + 0.5


void t0_int( void ) interrupt 1
{
  static uchar prescaler = PRESC_1S;

  TH0 |= 0xC0;			// shorten T0 to 16384
  if( --prescaler == 0 ){
    prescaler = PRESC_1S;
    if( F_1min ){
      prescaler = PRESC_1M;
      F_1min = 0;
    }
    if( F_1hour ){
      prescaler = PRESC_1H;
      F_1hour = 0;
    }
    F_1sec = 1;
  }
}


/************************************************************************/
/*									*/
/*				Main					*/
/*									*/
/************************************************************************/

void main( void )
{
  lcd_init();

  time.day = 16;
  time.month = 3;
  time.year = 3;

  ET0 = 1;
  EA = 1;
  TMOD = 1;
  TR0 = 1;

  for(;;){
    if( F_1sec ){
      F_1sec = 0;
      clock();
      display_clock();
    }
  }
}