/* $Id$

This file is part of R²C²
Copyright © 2010  Mikkosoft Productions, Mikko Rasa
Distributed under the GPL
*/

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

#define BIT(n) (1<<(n))
#define NOP() __asm__("nop");

uint8_t digits[11] =
{
	0x3F,
	0x06,
	0x5B,
	0x4F,
	0x66,
	0x6D,
	0x7D,
	0x07,
	0x7F,
	0x6F,
	0x40
};

uint16_t read_input(void);
uint16_t read_input_filtered(void);
void write_serial(uint8_t);
void write_7seg(uint8_t);

uint8_t speed = 0;
uint16_t funcs = 0;
volatile uint8_t ticks = 0;
volatile uint8_t rx_buf[3];
volatile uint8_t rx_fill = 0;

ISR(TIMER1_COMPA_vect)
{
	if(ticks<255)
		++ticks;
}

ISR(USART_RX_vect)
{
	uint8_t c = UDR0;
	if(rx_fill==0)
	{
		if(c=='A' || c=='S')
			rx_buf[rx_fill++] = c;
	}
	else
	{
		rx_buf[rx_fill++] = c;
		if(rx_buf[0]=='A' && rx_fill==3)
		{
			uint8_t n = (rx_buf[1]-'0')*10+(rx_buf[2]-'0');
			write_7seg(n/10);
			write_7seg(n%10);
			rx_fill = 0;
		}
		else if(rx_buf[0]=='S' && rx_fill==3)
		{
			speed = (rx_buf[1]-'0')*10+(rx_buf[2]-'0');
			rx_fill = 0;
		}
	}
}

int main()
{
	uint16_t state = 0;

	DDRD = 0x02;   // 00000010
	PORTD = 0xFC;  // 11111100
	DDRB = 0x3F;   // 00111111
	PORTB = 0x0F;  // 00001111

	write_7seg(10);
	write_7seg(10);

	// 9600 baud, 8N1
	UBRR0H = 0;
	UBRR0L = 103;
	UCSR0C = BIT(UCSZ00) | BIT(UCSZ01);
	UCSR0B = BIT(RXEN0) | BIT(TXEN0) | BIT(RXCIE0);

	TCCR1A = 0;
	TCCR1B = BIT(WGM12) | BIT(CS12);
	OCR1AH = 24;
	OCR1AL = 106;
	TIMSK1 = BIT(OCIE1A);

	sei();

	while(1)
	{
		uint16_t toggled;
		uint8_t i;
		uint16_t input;

		input = read_input_filtered();
		input ^= 0xFFFC;

		toggled = state^input;
		state = input;

		if((toggled&3)==2 && (state&1))
		{
			uint8_t action = 0;
			if(state&2)
			{
				if(speed<14)
				{
					++speed;
					action = 1;
				}
			}
			else
			{
				if(speed>0)
				{
					--speed;
					action = 1;
				}
				else if(ticks>10)
					action = 2;
			}

			if(action==1)
			{
				write_serial('S');
				write_serial('0'+speed/10);
				write_serial('0'+speed%10);
			}
			else if(action==2)
				write_serial('R');

			ticks = 0;
		}

		for(i=0; i<14; ++i)
		{
			uint16_t bit = 4<<i;
			if(toggled&~state&bit)
			{
				if(i==0)
					write_serial('N');
				else if(i==1)
					write_serial('P');
				else
				{
					uint8_t f = i-2;
					uint16_t fbit = 1<<f;
					funcs ^= fbit;
					write_serial((funcs&fbit) ? 'H' : 'L');
					write_serial('0'+f);
				}
			}
		}
	}
}

uint16_t read_input(void)
{
	uint8_t row;
	uint16_t input = 0;

	for(row=0; row<4; ++row)
	{
		uint8_t pins;

		PORTB = (PORTB|0x0F)&~(1<<row);
		NOP();
		NOP();
		NOP();
		NOP();
		NOP();
		NOP();
		pins = PIND>>2;
		input |= pins&3;
		input |= (pins&0x3C)<<(row*4);
	}

	return input;
}

uint16_t read_input_filtered(void)
{
	uint16_t valid = 0xFFFF;
	uint16_t prev;
	uint16_t input;
	uint8_t i;

	prev = read_input();
	for(i=0; i<20; ++i)
	{
		input = read_input();
		valid &= ~(input^prev);
		prev = input;
	}

	return input&valid;
}

void write_serial(uint8_t c)
{
	while(!(UCSR0A&(1<<UDRE0))) ;
	UDR0 = c;
}

void write_7seg(uint8_t n)
{
	uint8_t segs = ~digits[n];
	uint8_t i;
	for(i=0; i<8; ++i)
	{
		PORTB &= ~0x20;
		if(segs&0x80)
			PORTB |= 0x10;
		else
			PORTB &= ~0x10;
		PORTB |= 0x20;
		segs <<= 1;
	}
}