/*
 * neilsinterruptechoserial.c
 *
 * Created: 28.4.2015 10:43:13
 *  Author: janiyli
 */ 


//
//
// hello.ftdi.44.echo.interrupt.c
//
// 115200 baud FTDI character echo, interrupt version
//
// set lfuse to 0x7E for 20 MHz xtal
//
// Neil Gershenfeld
// 12/8/10
//
// (c) Massachusetts Institute of Technology 2010
// Permission granted for experimental and personal use;
// license for commercial sale available from MIT.
//

#include <avr/io.h>
#define F_CPU 20000000UL
#include <util/delay.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>

#define output(directions,pin) (directions |= pin) // set port direction for output
#define set(port,pin) (port |= pin) // set port pin
#define clear(port,pin) (port &= (~pin)) // clear port pin
#define pin_test(pins,pin) (pins & pin) // test for port pin
#define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set
#define bit_delay_time 102//for 9600baud//8.5 // bit delay for 115200 with overhead
#define bit_delay() _delay_us(bit_delay_time) // RS232 bit delay
#define half_bit_delay() _delay_us(bit_delay_time/2) // RS232 half bit delay
#define char_delay() _delay_ms(10) // char delay

#define serial_port PORTA
#define serial_direction DDRA
#define serial_pins PINA
#define serial_pin_in (1 << PA0)
#define serial_pin_out (1 << PA1)
#define serial_interrupt (1 << PCIE0)
#define serial_interrupt_pin (1 << PCINT0)

#define max_buffer 25

void get_char(volatile unsigned char *pins, unsigned char pin, char *rxbyte) {
	//
	// read character into rxbyte on pins pin
	//    assumes line driver (inverts bits)
	//
	*rxbyte = 0;
	while (pin_test(*pins,pin))
	//
	// wait for start bit
	//
	;
	//
	// delay to middle of first data bit
	//
	half_bit_delay();
	bit_delay();
	//
	// unrolled loop to read data bits
	//
	if pin_test(*pins,pin)
	*rxbyte |= (1 << 0);
	else
	*rxbyte |= (0 << 0);
	bit_delay();
	if pin_test(*pins,pin)
	*rxbyte |= (1 << 1);
	else
	*rxbyte |= (0 << 1);
	bit_delay();
	if pin_test(*pins,pin)
	*rxbyte |= (1 << 2);
	else
	*rxbyte |= (0 << 2);
	bit_delay();
	if pin_test(*pins,pin)
	*rxbyte |= (1 << 3);
	else
	*rxbyte |= (0 << 3);
	bit_delay();
	if pin_test(*pins,pin)
	*rxbyte |= (1 << 4);
	else
	*rxbyte |= (0 << 4);
	bit_delay();
	if pin_test(*pins,pin)
	*rxbyte |= (1 << 5);
	else
	*rxbyte |= (0 << 5);
	bit_delay();
	if pin_test(*pins,pin)
	*rxbyte |= (1 << 6);
	else
	*rxbyte |= (0 << 6);
	bit_delay();
	if pin_test(*pins,pin)
	*rxbyte |= (1 << 7);
	else
	*rxbyte |= (0 << 7);
	//
	// wait for stop bit
	//
	bit_delay();
	half_bit_delay();
}

void put_char(volatile unsigned char *port, unsigned char pin, char txchar) {
	//
	// send character in txchar on port pin
	//    assumes line driver (inverts bits)
	//
	// start bit
	//
	clear(*port,pin);
	bit_delay();
	//
	// unrolled loop to write data bits
	//
	if bit_test(txchar,0)
	set(*port,pin);
	else
	clear(*port,pin);
	bit_delay();
	if bit_test(txchar,1)
	set(*port,pin);
	else
	clear(*port,pin);
	bit_delay();
	if bit_test(txchar,2)
	set(*port,pin);
	else
	clear(*port,pin);
	bit_delay();
	if bit_test(txchar,3)
	set(*port,pin);
	else
	clear(*port,pin);
	bit_delay();
	if bit_test(txchar,4)
	set(*port,pin);
	else
	clear(*port,pin);
	bit_delay();
	if bit_test(txchar,5)
	set(*port,pin);
	else
	clear(*port,pin);
	bit_delay();
	if bit_test(txchar,6)
	set(*port,pin);
	else
	clear(*port,pin);
	bit_delay();
	if bit_test(txchar,7)
	set(*port,pin);
	else
	clear(*port,pin);
	bit_delay();
	//
	// stop bit
	//
	set(*port,pin);
	bit_delay();
}

void put_string(volatile unsigned char *port, unsigned char pin, char *str) {
	//
	// print a null-terminated string
	//
	static int index;
	index = 0;
	do {
		//put_char(port, pin, str[index]);
		++index;
	} while (str[index] != 0);
}

ISR(PCINT0_vect) {
	//
	// pin change interrupt handler
	//
	static char chr;
	static char buffer[max_buffer] = {0};
	static int index;
	get_char(&serial_pins, serial_pin_in, &chr);
	//put_string(&serial_port, serial_pin_out, "hello.ftdi.44.echo.interrupt.c: you typed \"");
	buffer[index++] = chr;
	if (index == (max_buffer-1))
	index = 0;
	//put_string(&serial_port, serial_pin_out, buffer);
	//put_char(&serial_port, serial_pin_out, '\"');
	//put_char(&serial_port, serial_pin_out, 10); // new line
	if (chr == 'a') PORTB |= (1 << PB2);
	if (chr == 'b') PORTB &= ~(1 << PB2);
	
}

int main(void) {
	//
	// main
	//
	// set clock divider to /1
	//
	CLKPR = (1 << CLKPCE);
	CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
	//
	// initialize output pins
	//
	set(serial_port, serial_pin_out);
	output(serial_direction, serial_pin_out);
	//
	// set up pin change interrupt on input pin
	//
	set(GIMSK, serial_interrupt);
	set (PCMSK0, serial_interrupt_pin);
	sei();
	//
	//Init Led
	//
	DDRB |= (1 << PB2);
	PORTB |= (1 <<PB2);
	//
	// main loop
	//
	while (1) {
		//
		// wait for interrupt
		//
		;
	}
}