/* ---------------------------------------------------------------------------
** This software is in the public domain, furnished "as is", without technical
** support, and with no warranty, express or implied, as to its usefulness for
** any purpose.
**
** ioisr.c
**
** Beschrijving:	BigAVR LCD module
** Target:			AVR mcu
** Build:			avr-gcc -std=c99 -Wall -O3 -mmcu=atmega128 -D F_CPU=8000000UL -c lcd.c
**					avr-gcc -g -mmcu=atmega128 -o lcd.elf lcd.o
**					avr-objcopy -O ihex lcd.elf lcd.hex
**					or type 'make'
** Author: 			dkroeske@gmail.com
** -------------------------------------------------------------------------*/

#define F_CPU 8e6

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>

#define LCD_E 	6  // RA6 UNI-6
#define LCD_RS	4  // RA4 UNI-6

void lcd_strobe_lcd_e(void);
void init_4bits_mode(void);
void lcd_write_string(char *str);
void lcd_write_data(unsigned char byte);
void lcd_write_cmd(unsigned char byte);
void lcd_clear(void);


/******************************************************************
short:			Busy wait number of millisecs
inputs:			int ms (Number of millisecs to busy wait)
outputs:
notes:			Busy wait, not very accurate. Make sure (external)
clock value is set. This is used by _delay_ms inside
util/delay.h
Version :    	DMK, Initial code
*******************************************************************/
void wait( int ms ) {
	for (int i=0; i<ms; i++) {
		_delay_ms( 1 );		// library function (max 30 ms at 8MHz)
	}
}

/******************************************************************
short:			Strobe LCD module E pin --__
inputs:
outputs:
notes:			According datasheet HD44780
Version :    	DMK, Initial code
*******************************************************************/
void lcd_strobe_lcd_e(void) {
	PORTA |= (1<<LCD_E);	// E high
	_delay_ms(1);			// nodig
	PORTA &= ~(1<<LCD_E);  	// E low
	_delay_ms(1);			// nodig?
}



/******************************************************************
short:			Init LCD module in 4 bits mode.
inputs:
outputs:
notes:			According datasheet HD44780 table 12
Version :    	DMK, Initial code
*******************************************************************/
void init_4bits_mode(void) {
	// PORTC output mode and all low (also E and RS pin)
	DDRD = 0xFF;
	DDRA = 0xFF;
	PORTC = 0x00;
	PORTA = 0x00;
	//PORTA = 0xFF;

	// Step 2 (table 12)
	PORTC = 0x20;	// function set
	lcd_strobe_lcd_e();

	// Step 3 (table 12)
	PORTC = 0x20;   // function set
	lcd_strobe_lcd_e();
	PORTC = 0x80;
	lcd_strobe_lcd_e();

	// Step 4 (table 12)
	PORTC = 0x00;   // Display on/off control
	lcd_strobe_lcd_e();
	PORTC = 0xF0;
	lcd_strobe_lcd_e();

	// Step 4 (table 12)
	PORTC = 0x00;   // Entry mode set
	lcd_strobe_lcd_e();
	PORTC = 0x60;
	lcd_strobe_lcd_e();
}

/******************************************************************
short:			Writes string to LCD at cursor position
inputs:
outputs:
notes:			According datasheet HD44780 table 12
Version :    	DMK, Initial code
*******************************************************************/
void lcd_write_string(char *str) {
	// Het kan met een while:

	// while(*str) {
	// 	lcd_write_data(*str++);
	// }

	// of met een for:
	for(;*str; str++){
		lcd_write_data(*str);
	}
}


/******************************************************************
short:			Writes 8 bits DATA to lcd
inputs:			byte - written to LCD
outputs:
notes:			According datasheet HD44780 table 12
Version :    	DMK, Initial code
*******************************************************************/
void lcd_write_data(unsigned char byte) {
	// First nibble.
	PORTC = byte;
	PORTA |= (1<<LCD_RS);
	lcd_strobe_lcd_e();

	// Second nibble
	PORTC = (byte<<4);
	PORTA |= (1<<LCD_RS);
	lcd_strobe_lcd_e();
}

/******************************************************************
short:			Writes 8 bits COMMAND to lcd
inputs:			byte - written to LCD
outputs:
notes:			According datasheet HD44780 table 12
Version :    	DMK, Initial code
*******************************************************************/
void lcd_write_command(unsigned char byte) {
	// First nibble.
	PORTC = byte;
	PORTA &= ~(1<<LCD_RS);
	lcd_strobe_lcd_e();

	// Second nibble
	PORTC = (byte<<4);
	PORTA &= ~(1<<LCD_RS);
	lcd_strobe_lcd_e();
}


void lcd_clear() {
	lcd_write_command (0x01);						//Leeg display
	_delay_ms(2);
	lcd_write_command (0x80);						//Cursor terug naar start
}


/******************************************************************
short:			main() loop, entry point of executable
inputs:
outputs:
notes:			Slow background task after init ISR
Version :    	DMK, Initial code
*******************************************************************/
int main( void ) {
	// Init I/O
	DDRC = 0xFF;			// PORTD(7) output, PORTD(6:0) input
	PORTC = 0xFF;

	// Init LCD
	init_4bits_mode();
	
	_delay_ms(10);
	
	lcd_clear();

	// Write sample string
	lcd_write_string("Hello world!");

	// Loop forever
	while (1) {
		PORTC ^= (1<<0);	// Toggle PORTD.7
		wait( 250 );
		
	}

	return 1;
}