/*

 lcd.c

 LCD Routines for Orangutan/WinAVR. Runs on either the ATMega8 or ATmega168 versions.

 Substantially modified from a post on the Pololu forum.
 The required delays included here are generously in accord with the LCD data sheet, and should be 
 independent of the clock speed as long as F_CPU is set correctly (>= 1 MHz)
 
 Tested with compiler optimization -O0 and -O3, 
 
 Added a routine -- LCDGotoXY (X,Y) -- which allows printing to any position on the display.
 X = character position (0-39), Y=line (0 or 1).

 Needed includes: <util/delay.h>, <avr/io.h>

 Jim Remington, sjames_remington at yahoo dot com

*/

//Function prototypes

void LCDInit(void);
void LCDSendData(unsigned char data);
void LCDSendCommand(unsigned char command);
void LCDPrintString(const unsigned char *string);
void LCDGotoXY(unsigned char x,unsigned char y);

#define F_CPU 8000000UL 
#include <avr/io.h>
#include <util/delay.h>

// useful defines (LCD commands)

#define LCD_Clear 0x01
#define LCD_Line1 0x80
#define LCD_Line2 0xC0


/*
Send lower 4 bits of data byte to display
*/
void	LCDSendNibble( unsigned char data )
{
	data &= 0x0F;			//lower 4 bits of data
	data <<= 3;
	PORTB &= ~0x38;			//clear LCD bus bits 456
	PORTB |= (data & 0x38);	//or in data
	data <<= 1;
	PORTD &= ~0x80;			//same for top bit on PORTD.7
	PORTD |= (data & 0x80);
	_delay_us(1);
	PORTD |= (1<<4);		//E = 1
	_delay_us(2);			//required minimum 1 us delay
	PORTD &= ~(1<<4);		//E = 0
	_delay_us(1);
}

/*
Send a character to the LCD display
*/

void	LCDSendData( unsigned char data )

{
	PORTD &= ~(1<<3);	//R/W =0
	PORTD |= (1<<2);	//RS = 1;
	LCDSendNibble( data >> 4 );
	LCDSendNibble( data );
	_delay_us(100);			//38 us typically needed to complete this action
}

/*
Send a command to display. Required delay time depends on the command and the 
LCD controller clock frequency -- here assumed to be the minimum 190 kHz
*/
void	LCDSendCommand( unsigned char command )

{
	PORTD &= ~(3<<2);		// R/W=0, RS = 0;
	LCDSendNibble(command>> 4 );
	LCDSendNibble(command);
	_delay_ms(3);			//maximum required is 2.1 ms for "clear display"
}
// print a string constant

void	LCDPrintString( const unsigned char *str )
{
    while (*str != 0) LCDSendData( *str++ );
}

// set print position to (x,y) where y=line number (0 or 1), x = character position 0, 1, etc.

void LCDGotoXY(unsigned char x, unsigned char y)
{
	volatile unsigned char ddram_addr;
	ddram_addr=0x80;			//initialize data ram address to 0 (default)
	if (y==1) ddram_addr=0xC0;  //start print at line 2, DDRAM address 0x40
	LCDSendCommand(ddram_addr+ (x&0x7F) );
}
/*
Initialize the LCD Display, timing requirements taken from datasheet
Set PORTB.3,4,5 to DB 4,5,6
Set PORTD.2,3,4,7 to RS, R/W, E and DB7
Send required start-up sequence to set 4 bit interface, 2 lines, 5x8 characters and clear display
*/
	
void	LCDInit( void )
{
	DDRB |= (7<<3);
	DDRD |= (1<<7) | (7<<2);
	PORTD &= ~(7<<2);		// E=0,R/W=0, RS = 0;
	_delay_ms(20);			//required startup sequence from power-on (see datasheet)
	LCDSendNibble(0x03);	//set interface=8 bits
	_delay_ms(10);			//wait at least 5 ms	
	LCDSendNibble(0x03);	//set interface=8 bits
	_delay_ms(1);			//wait at least 100 us
	LCDSendNibble(0x03);	//set interface=8 bits
	_delay_ms(1);			//wait at least 100 us
	LCDSendNibble(0x02);	//set interface=4 bits
	_delay_ms(1);			//delays after this are built into SendCommand
	LCDSendCommand(0x28);	//set interface=4 bits, 2 lines, 5x8 characters
	LCDSendCommand(0x08);	//display off, cursor off, blink off 
	LCDSendCommand(0x01);	//clear display
	LCDSendCommand(0x06);	//entry mode set, cursor shifts right after character rcvd.
	LCDSendCommand(0x0D);	//0b01DCB  D=1:Display on, C=1:cursor on, B=1:Blink on
}