lcdfuncs.h

This Program Cotains Eeprom Read-write functions, 4 Bit LCD interface routines, Keyboard Interface w

/*	These routines interface a Hitachi LM016 LCD display module
	to P0 of the AT89C52 using the 4 bit data bus interface
	I/O connections are as defined below
	P0.4 - P0.7 = DB.4 - DB.7, P0.2 = EN, P0.1 = R/W*, P0.0 = RS */


void wait_LCD_busy(void);
void init_2_line_LCD(void);
void write_LCD_byte(bit reg_val,unsigned char byte_val);
unsigned char read_LCD_byte(bit reg_val);
void write_LCD_line(unsigned char start_add,unsigned char *line_text);
void init_delay(void);
void clear_line(bit line_val);
void strobe_LCD(void);
void clear_lcd(void);
#define LCD_CONTROL 0
#define LCD_DATA 1
#define LINE_1 0x80
#define LINE_2 0xC0
#define UPPER_LINE 0
#define LOWER_LINE 1

/*
#define CLEAR_DISPLAY   0x01
#define CURSOR_HOME     0x02
#define DISPLAY_OFF		0x08
#define CURSOR_OFF      0x0C
#define CURSOR_ON       0x0D
#define CURSOR_BLINK_2  0x0E
#define CURSOR_BLINK_1  0x0F
#define SHIFT_LEFT      0x18
#define SHIFT_RIGHT     0x1C
*/
sbit RS = P0^1;
sbit RW = P0^2;
sbit EN = P0^3;

static unsigned char char_add,data_byte;
code unsigned char init_bytes[5] = {0x28,0x08,0x01,0x06,0x0c};
//code unsigned char init_bytes[6] = {0x32,0x2c,0x06,0x0c,0x01,0x02};

void init_2_line_LCD(void)
{
	unsigned char temp;

	init_delay();
	P0 = 0x31;
	strobe_LCD();
	init_delay();
	strobe_LCD();
	init_delay();
	strobe_LCD();
	wait_LCD_busy();
	P0 = 0x21;
	strobe_LCD();
	wait_LCD_busy();

	
	for(temp = 0;temp < 5;temp++)
	{
		write_LCD_byte(LCD_CONTROL,init_bytes[temp]);
	}
//	write_LCD_byte(LCD_CONTROL,0x02);
	/*display on,cursor off,blink off*/
}

void init_delay()
{
	data_byte = 40;
	while(data_byte > 0)
	{
		for(char_add = 0;char_add < 150;char_add++)
		{
		}
		data_byte--;
	}
}

void write_LCD_byte(bit reg_val,unsigned char byte_val)
{
	P0 = (byte_val & 0xf0)+ 0x01;
	if(reg_val == LCD_DATA)
	{
		RS = 1;
	}
	strobe_LCD();
	P0 = (byte_val << 4)+ 0x01;
	if(reg_val == LCD_DATA)
	{
		RS = 1;
	}
	strobe_LCD();
	wait_LCD_busy();
}

unsigned char read_LCD_byte(bit reg_val)
{
	/*unsigned char temp;*/

	P0 = 0xf5; /*make P0 upper nibble i/p and set R/W**/
	if(reg_val == LCD_DATA)
	{
		RS = 1; /*set RS*/
	}
	EN = 1;
	data_byte = P0 & 0xf0;	/*read high order nibble*/
	EN = 0;
	EN = 1;
	data_byte = data_byte + (P0 >> 4); /*read low order nibble and format*/
	EN = 0;
	P0 = 0x01; /*return P0 to inactive state*/
	return data_byte;
}

void wait_LCD_busy(void)
{
	while((read_LCD_byte(LCD_CONTROL) & 0x80) == 0x80);
}

void write_LCD_line(unsigned char start_add,unsigned char *line_text)
{
	char_add = 0;
	write_LCD_byte(LCD_CONTROL,start_add);
	while(*(line_text + char_add) != '\0')
	{
		write_LCD_byte(LCD_DATA,*(line_text + char_add));
		char_add++;
	}
}

/*
void clear_line(bit line_val)
{
	char_add = 0xc0;
	if(line_val == UPPER_LINE)
	{
		char_add = 0x80;
	}
	write_LCD_byte(LCD_CONTROL,char_add);	
	for(char_add = 0;char_add < 16;char_add++)
	{
		write_LCD_byte(LCD_DATA,' ');
	}
}			*/

void strobe_LCD(void)
{
	EN = 1;
	EN = 0;
}

void clear_lcd(void)
{
	clear_line(UPPER_LINE);
	clear_line(LOWER_LINE);
write_LCD_byte(LCD_CONTROL,0x01);
write_LCD_byte(LCD_CONTROL,0x02);
}