#include "drivers/uart_tx.h"
#include <avr/io.h>
#include <util/delay.h>

void wait_strobe_on() { // active low
	while((PIND >> PD2) & 1) {};
}

void wait_strobe_off() {
	while(~(PIND >> PD2) & 1) {};
}

void ack_on() { // active low
	PORTD &= ~(1 << PD3);
}

void ack_off() {
	PORTD |= (1 << PD3);
}

void busy_on() { // active high
	PORTB |= (1 << PB4);
}

void busy_off() {
	PORTB &= ~(1 << PB4);
}

int main(void) {
	// STROBE input is on PD2
	// PB0-PB3 and PD4-PD7 are data inputs
	DDRD = (1 << PD3); // ACK output
	DDRB = (1 << PB4); // BUSY output

	// pull-up per default
	PORTD |= (1 << PD2) |  (1 << PD3);

	uint8_t i, data;

	for(;;) {
		wait_strobe_on();
		data = (PIND & 0xF0) | (PINB & 0x0F);
		busy_on();
		ack_on();
		_delay_us(10); // 5 us minimum
		ack_off();

		// this blocks until written
		uart_putc(data);

		busy_off();
		// make sure we are not reading the same char again
		wait_strobe_off();
	}
}