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

int main(void) {
	int i;
	InitSwUART(); // init UART
	sei(); // enable interrupts

	DDRB |= (1 << PB0);
	PORTB &= ~(1 << PB0); // toggle PB0 (trig)
	PORTB |= (1 << PB0);
	PORTB &= ~(1 << PB0);

	unsigned char a[] = {0xFF, 0x00, 0x01, 0x82, 0x83};

	for(i = 0; i < 5; i++) {
		put_char(a[i]);
	}

	while(1) {
	}
}

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// Some I/O and interrupt specific defines (hardware setup)
#define TX_PIN	PB4
#define RX_PIN	PB2 // INT0 have to be on this pin...
#define TRXDDR	DDRB
#define TRXPORT	PORTB
#define TRXPIN	PINB

#define ENABLE_TIMER_INTERRUPT() (TIMSK |= (1 << OCIE0A))
#define DISABLE_TIMER_INTERRUPT() (TIMSK &= ~(1 << OCIE0A))
#define ENABLE_EXTERNAL_INTERRUPT() (GIMSK |= (1 << INT0))
#define DISABLE_EXTERNAL_INTERRUPT() (GIMSK &= ~(1 << INT0))


#define SET_TX_PIN() (TRXPORT |= (1 << TX_PIN))
#define CLEAR_TX_PIN() (TRXPORT &= ~(1 << TX_PIN))
#define GET_RX_PIN() (TRXPIN & (1 << RX_PIN))

#define TICK_ONEANDHALF	75
#define TICK_ONE		50


// Functions
void InitSwUART(void);
void put_char(const unsigned char c);
void print_string(const unsigned char *data);

// Variables
typedef enum {
	IDLE,
	TRANSMIT,
	RECEIVE,
	DATA_PENDING
}states;

static volatile states SwUART_state;
static volatile unsigned char SwUART_TXData;
static volatile unsigned char SwUART_TXBitCount;
static volatile unsigned char SwUART_RXData;
static volatile unsigned char SwUART_RXBitCount;

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// 8MHz clock and 19200 as baudrate designed for ATtiny45
// No parity bit, 8 data bits, 1 stop bit

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

ISR(TIM0_COMPA_vect) { // timer interrupt handler

	// transmit byte
	if(SwUART_state == TRANSMIT) {
		if(SwUART_TXBitCount < 8) {
			if(SwUART_TXData & 0x01) {
				SET_TX_PIN(); // send a logic 1
			}
			else {
				CLEAR_TX_PIN(); // send a logic 0
			}

			SwUART_TXData = SwUART_TXData >> 1;
			SwUART_TXBitCount++;
		}

		// send stop bit
		else if(SwUART_TXBitCount == 8) {
			SET_TX_PIN();
			SwUART_TXBitCount++;
		}

		// done transmitting
		else {
			DISABLE_TIMER_INTERRUPT();
			SwUART_state = IDLE;
		}	
	}

	// receive byte
	else if(SwUART_state == RECEIVE) {
		OCR0A = TICK_ONE; // count one period
		// receiving, LSB first
		if(SwUART_RXBitCount < 8) {
			if(GET_RX_PIN() != 0) {
				SwUART_RXData = 0x80; // if a logic one let the data mirror this
			}
			SwUART_RXData = (SwUART_RXData >> 1); // shift due to LSB first
			SwUART_RXBitCount++;
		}
		// done receiving
		else {
			SwUART_state = DATA_PENDING; // one byte received enter DATA_PENDING
			DISABLE_TIMER_INTERRUPT();
			GIFR |= (1 << INTF0); // reset flag to not enter external intrrupt one extra time
			ENABLE_EXTERNAL_INTERRUPT(); // enable external interrupt to receive more bytes
		}
	}

	// error, should not occur -> go to safe state
	else {
		SwUART_state = IDLE;
	}

}

ISR(INT0_vect) { // external interrupt handler
	SwUART_state = RECEIVE;
	
	DISABLE_EXTERNAL_INTERRUPT(); // disable external interrupt during data bits

	DISABLE_TIMER_INTERRUPT(); // disable timer interrupt to change register
	TCNT0 = 0; // clear counter
	OCR0A = TICK_ONEANDHALF; // wait one and a half period
	ENABLE_TIMER_INTERRUPT(); // enable timer again
}

void InitSwUART(void) {
	TRXDDR |= (1 << TX_PIN); // set TX pin as output
	TRXDDR &= ~(1 << RX_PIN); // set RX pin as input


	// Timer0 init
	TCCR0A |= (1 << WGM01); // CTC mode
	TCCR0B |= (1 << CS01); // prescaler 8
	TIMSK |= (1 << OCIE0A); // interrupt on compare
	SET_TX_PIN(); // set TX-line to idle

	// External interrupt
	MCUCR |= (1 << ISC01); // interrupt on falling edge
	ENABLE_EXTERNAL_INTERRUPT(); // turn external interrupt on

	SwUART_state = IDLE; // set init state
}

void put_char(const unsigned char c) {
	while(SwUART_state != IDLE) {} // don't send while busy receiving or transmitting

	SwUART_state = TRANSMIT;
	SwUART_TXData = c;
	SwUART_TXBitCount = 0;

	TCNT0 = 0; // clear counter
	OCR0A = TICK_ONE; // tick one period
	TIFR |= (1 << OCF0A); // clear flag

	CLEAR_TX_PIN(); // clear TX-line... start of preamble
	ENABLE_TIMER_INTERRUPT();
}

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void put_char(const unsigned char c)
  {
   while(SwUART_state != IDLE) {} // don't send while busy receiving or transmitting
   // Hoppla 1
   SwUART_state = TRANSMIT; // Hoppla 2
   SwUART_TXData = c; // Hoppla 3
   SwUART_TXBitCount = 0; // Hoppla 4
   // Hoppla 5
   TCNT0 = 0; // clear counter
   OCR0A = TICK_ONE; // tick one period
   TIFR |= (1 << OCF0A); // clear flag

   CLEAR_TX_PIN(); // clear TX-line... start of preamble
   ENABLE_TIMER_INTERRUPT();
}

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   SwUART_TXData = c;
   SwUART_TXBitCount = 0;
   SwUART_state = TRANSMIT;

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void InitSwUART(void) {
	TRXDDR |= (1 << TX_PIN); // set TX pin as output
	TRXDDR &= ~(1 << RX_PIN); // set RX pin as input


	// Timer0 init
	TCCR0A |= (1 << WGM01); // CTC mode
	TCCR0B |= (1 << CS01); // prescaler 8
	TIMSK |= (1 << OCIE0A); // interrupt on compare
	SET_TX_PIN(); // set TX-line to idle

	// External interrupt
	MCUCR |= (1 << ISC01); // interrupt on falling edge
	ENABLE_EXTERNAL_INTERRUPT(); // turn external interrupt on

	SwUART_state = IDLE; // set init state
}