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

void display_init() {
	// PC5, PC6, PC7: output (VFD RS, RW, E), RS=0, RW=1, E=1
	// PD: output (VFD DB) - can be switched to input (pullup not needed)
	PORTC |= _BV(PC6) | _BV(PC7);
	DDRC |= _BV(PC5) | _BV(PC6) | _BV(PC7);
	PORTD = 0x00;
	DDRD = 0xff;
}

uint8_t display_read_ir() {
	// switch PD to input
	DDRD = 0x00;
	// E=0 (enable/clock) RS=0 (IR) RW=1 (read)
	PORTC = (PORTC & ~(_BV(PC5) | _BV(PC7))) | _BV(PC6);
	_delay_us(0.23);
	// E=1 (enable/clock)
	PORTC |= _BV(PC7);
	_delay_us(0.16);
	uint8_t data = PIND;
	_delay_us(0.23 - 0.16);
	// E=0 (enable/clock)
	PORTC &= ~_BV(PC7);
	_delay_us(0.01);
	// reset to idle
	PORTC = _BV(PC6) | _BV(PC7);
	DDRD = 0xff;
	return data;
}

uint8_t display_read_dr() {
	// switch PD to input
	DDRD = 0x00;
	// E=0 (enable/clock) RS=1 (IR) RW=1 (read)
	PORTC = (PORTC & ~_BV(PC7)) | (_BV(PC5) | _BV(PC6));
	_delay_us(0.23);
	// E=1 (enable/clock)
	PORTC |= _BV(PC7);
	_delay_us(0.16);
	uint8_t data = PIND;
	_delay_us(0.23 - 0.16);
	// E=0 (enable/clock)
	PORTC &= ~_BV(PC7);
	_delay_us(0.01);
	// reset to idle
	PORTC = _BV(PC6) | _BV(PC7);
	DDRD = 0xff;
	return data;
}

void display_write_ir(uint8_t data) {
	// E=0 (enable/clock) RS=0 (IR) RW=0 (write)
	PORTC &= ~(_BV(PC5) | _BV(PC6) | _BV(PC7));
	_delay_us(0.23);
	// E=1 (enable/clock)
	PORTC |= _BV(PC7);
	// data
	PORTD = data;
	_delay_us(0.23);
	// E=0 (enable/clock)
	PORTC &= ~_BV(PC7);
	_delay_us(0.01);
	// reset to idle
	PORTC = _BV(PC6) | _BV(PC7);
	PORTD = 0x00;
}

void display_write_dr(uint8_t data) {
	// E=0 (enable/clock) RS=1 (IR) RW=0 (write)
	PORTC = (PORTC & ~(_BV(PC6) | _BV(PC7))) | _BV(PC5);
	_delay_us(0.23);
	// E=1 (enable/clock)
	PORTC |= _BV(PC7);
	// data
	PORTD = data;
	_delay_us(0.23);
	// E=0 (enable/clock)
	PORTC &= ~_BV(PC7);
	_delay_us(0.01);
	// reset to idle
	PORTC = _BV(PC6) | _BV(PC7);
	PORTD = 0x00;
}


bool display_wait_ready() {
	// if the busy flag never goes high, we'll run into a deadlock here.
	// let's put a deadline on the wait loop.
	for (uint8_t i = 0; i < 100; i++) {
		// read_ir() takes about 500ns
		if (display_read_ir() & _BV(7)) return true;
		// wait 10us until the next status read
		_delay_us(10 - 0.5);
	}
	return false;
}

void display_write(uint8_t command, const uint8_t *data, uint8_t length) {
	if (display_wait_ready()) {
		display_write_ir(command);
		for (uint8_t i = 0; i < length; i++) {
			display_write_dr(data[i]);
		}
	}
}