creativiteit begint op te raken

/*
 * opdracht2c.c
 *
 * Created: 17/02/2018 20:27:52
 * Author : Willem
 */

#define F_CPU 16000000
#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include <stdlib.h>

char leesNummer();
void binaryDisplay(int x);
ISR(USART_RXC_vect);
int teller = 0;

void writeChar(char x);
void writeString(char st[]);
void writeInt(int i);

int main(void) {
	sei();

	UCSR0B = (1 << TXEN0); // Enable de USART Transmitter
	UCSR0C |= (1 << UCSZ01 | 1 << UPM01) ; /* 7 data bits, */
	UCSR0B |= (1 << TXEN0) | (1 << RXEN0) |  (1 << RXCIE0);
	UBRR0H=00;
	UBRR0L=103; //baudrade 9600 bij
	DDRB = 0b00011111;

	while (1) {
		for(uint8_t i = 0; i <= 1; i++){
			if(i == 0){
				PORTB &= ~(1 << 4);
				_delay_ms(1000);
				writeInt(teller);
			}
			else if(i == 1){
				if(teller > 0){
					PORTB &= ~(1 << 3);
					PORTB &= ~(1 << 2);
					PORTB &= ~(1 << 1);
					PORTB &= ~(1 << 0);
					binaryDisplay(teller);
					teller = teller - 1;
					PORTB |= (1 << 4);
					i = -1;
					}
				_delay_ms(1000);
			}
		}
		PORTB &= ~(1 << 3);
		PORTB &= ~(1 << 2);
		PORTB &= ~(1 << 1);
		PORTB &= ~(1 << 0);
	}
	return (0);
}

void binaryDisplay(int x){
	if(x >= 8){
		PORTB |= (1 << 3);
		x = x - 8;
	}
	if(x >= 4){
		PORTB |= (1 << 2);
		x = x - 4;
	}
	if(x >= 2){
		PORTB |= (1 << 1);
		x = x - 2;
	}
	if(x >= 1){
		PORTB |= (1 << 0);
		x = x - 1;
	}
}
char leesNummer() {
	while(!(UCSR0A & (1<<RXC0)));
	return UDR0;
}
int hexToInt(char c) {
	char hex[] = "0123456789ABCDEF"; // de HEX waarden
	int output = 0; // de output variable

	for(int i = 0; i <= 15; i++) { // loop door de hex char array
		if(hex[i] == c) { output = i; } // als de hex waarde gelijk is aan de ingegeven waarde is dat de output
	}

	return output; // return de output
}

ISR(USART_RX_vect){
	char c = leesNummer();
	teller = hexToInt(c);
}

void writeChar(char x) {
	while(~UCSR0A & (1 << UDRE0));
	UDR0 = x;
}

void writeString(char st[]) {
	for(uint8_t i = 0 ; st[i] != 0 ; i++) {
		writeChar( st[i] );
	}
}

void writeInt(int i) {
	char buffer[8];
	itoa(i,buffer,10);
	writeString(buffer);
}