=================CHARCASE=================
#include "charcase.h"
#include <string.h>

void to_uppercase(char *s) {
	*s -= 32;
}

void to_lowercase(char *s) {
	*s += 32;
}

void invert_case(char *s) {
	if (*s >= 'a' && *s <= 'z') {
	    to_uppercase(s);
	} else if (*s >= 'A' && *s <= 'Z') {
	    to_lowercase(s);
	}
}

void invert_string(char *str) {
	int i;
	for (i = 0; i < strlen(str); i++) {
		invert_case(&str[i]);
	}
}
=================FIFO=================
#include <stdbool.h>
#include "AT91SAM9263.h"
#include "fifo.h"

void init_fifo (fifo *f) {
	f->head = 0;
	f->tail = 0;
}

void fifo_empty (fifo *f) {
	f->head = f->tail;
}

bool is_fifo_full(fifo *f) {
	return ((f->tail - f->head) == 1 || (f->head - f->tail) == BUFFERSIZE);
}

int fifo_put (fifo *f, char data) {
	if (is_fifo_full(f)) {
    		return -1;
	}

	f->buffer[f->head] = data;
	f->head = (f->head + 1) & BUFFERSIZE;
	return 1;
}

int fifo_get (fifo *f, char *data) {
	if (f->head != f->tail) {
		*data = f->buffer[f->tail];
		f->tail = (f->tail + 1) & BUFFERSIZE;
		return 1;
	} else {
		return -1;
	}
}

=================DBGU=================
#include <string.h>

#include "AT91SAM9263.h"
#include "dbgu.h"
#include "fifo.h"
#include "charcase.h"

#define THROUGHPUT 115200
#define NEWLINE 13

fifo f;

int init_dbgu() {
	AT91C_BASE_DBGU->DBGU_IDR = 0xFFFFFFFF;
	AT91C_BASE_DBGU->DBGU_CR = AT91C_US_RSTRX | AT91C_US_RXDIS;
	AT91C_BASE_DBGU->DBGU_CR = AT91C_US_RSTTX | AT91C_US_TXDIS;
	AT91C_BASE_PIOC->PIO_ASR = AT91C_PC31_DTXD | AT91C_PC30_DRXD;
	AT91C_BASE_PIOC->PIO_PDR = AT91C_PC31_DTXD | AT91C_PC30_DRXD;
	AT91C_BASE_DBGU->DBGU_BRGR = PROCESSOR_CLOCK / (THROUGHPUT * 16);
	AT91C_BASE_DBGU->DBGU_MR = AT91C_US_CHMODE_NORMAL | AT91C_US_PAR_NONE;
	AT91C_BASE_DBGU->DBGU_CR = AT91C_US_RXEN;
	AT91C_BASE_DBGU->DBGU_CR = AT91C_US_TXEN;
	init_fifo(&f);
	return 0;
}

void dbgu_print_newline() {
	while (!(AT91C_BASE_DBGU->DBGU_CSR & AT91C_US_TXRDY)) {}
	AT91C_BASE_DBGU->DBGU_THR = '\n';
	while (!(AT91C_BASE_DBGU->DBGU_CSR & AT91C_US_TXRDY)) {}
	AT91C_BASE_DBGU->DBGU_THR = '\r';
}

int dbgu_print_ascii() {
	char buf;
	int char_counter = 0;

	while (fifo_get(&f, &buf) == 1) {
		while (!(AT91C_BASE_DBGU->DBGU_CSR & AT91C_US_TXRDY)) {}
		invert_string(&buf);
		AT91C_BASE_DBGU->DBGU_THR = buf;
		char_counter++;
	}
	dbgu_print_newline();

	return char_counter;
}

int dbgu_read_ascii() {
	int counter = 0;

	while(1) {
		while (!(AT91C_BASE_DBGU->DBGU_CSR & AT91C_US_RXRDY)) {};
		char buf = AT91C_BASE_DBGU->DBGU_RHR & 0xFF;

		if (buf == NEWLINE) {
			break;
		}

		if (is_fifo_full(&f)) {
			dbgu_print_warning("fifo overflow occured");
		} else {
			fifo_put(&f, buf);
		}

		++counter;
	}

	return counter;
}

void dbgu_print_warning(char *msg) {
	dbgu_print_newline();

	int i;
	for (i = 0; i < strlen(msg); i++) {
		while (!(AT91C_BASE_DBGU->DBGU_CSR & AT91C_US_TXRDY)) {}
		AT91C_BASE_DBGU->DBGU_THR = msg[i];
	}

	dbgu_print_newline();
}
===============MAIN===================
#include "AT91SAM9263.h"
#include "dbgu.h"
#include <stdbool.h>

int main() {
	init_dbgu();

	while(1) {
	    dbgu_read_ascii();
	    dbgu_print_ascii();
	}
	return 0;
}




==================================