#define F_CPU 1000000UL

#include <stdio.h>
#include <stdlib.h>
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/signal.h>
#include <avr/delay.h>
#include "lcd.h"

#define BUF_SIZE 40
#define TRUE 1
#define FALSE 0


volatile unsigned char buf_in[BUF_SIZE], ptr_in;
unsigned char ptr_out;


SIGNAL (SIG_UART_RECV){

	PORTD = ~PORTD; //toggle LED when character received
	buf_in[ptr_in] = UDR; //put data into buffer
	ptr_in = ++ptr_in % BUF_SIZE; // update pointer
}


// sends a character to the serial port
int s_putc(char car){

	while( !(UCSRA & _BV(UDRE)) ); //wait for transmit buffer to be ready
	UDR = car; //send character

	return 0;
}


// reads a character from the serial port
int s_getc(void) {

char car;

	while(ptr_in == ptr_out); //wait for the buffer to contain at least one character
	car = buf_in[ptr_out]; //read first character from buffer
	ptr_out = ++ptr_out % BUF_SIZE; //point to next character

	return car;
}





void ioinit (void) {

	DDRD = 0x20;	//outputs : LED
	PORTD = 0x00;	//turn LED off at boot.
	DDRA = 0xFF;	// LCD : PA7:2 outputs, PA0:1 unused
	PORTA = 0x00;	//Start with LCD RS reset, for initialization.
	//set up USART
	UBRRH = 0x00;
	UBRRL = 12;		//Baud Rate = 9600
	UCSRA = 0x02;	//mode asynchrone, fast clock
	UCSRC = 0X86;	//asynchronous, no parity, one stop bit, 8 data bits
	UCSRB = 0x98;	//transmitter and receiver enabled, interrupts on receiver
	sei();			//enable global interrupts (hence receive buffer)
}

int main (void){

unsigned char car, car2=0;

	ioinit ();
	fdevopen(lcd_putc, s_getc, 0); // assign custom I/O functions to stdout & stdin
	init_lcd();	
	while(TRUE){ //display the LCD module's character table
		car = s_getc(); //press a key to show next character
		if (car == 13) { //press "Enter" to clear the screen and return to top left
			lcd_clear();
		}else
			lcd_putc(car2++); //display character

	}
}