Enable printf() with trace

trace.c

#define ITM_Port8(n)    (*((volatile unsigned char *)(0xE0000000+4*n)))
#define ITM_Port16(n)   (*((volatile unsigned short*)(0xE0000000+4*n)))
#define ITM_Port32(n)   (*((volatile unsigned long *)(0xE0000000+4*n)))

#define DEMCR           (*((volatile unsigned long *)(0xE000EDFC)))
#define TRCENA          0x01000000

struct __FILE { int handle; /* Add whatever is needed */ };
FILE __stdout;
FILE __stdin;

int fputc(int ch, FILE *f) {
    if (DEMCR & TRCENA) {
        while (ITM_Port32(0) == 0);
        ITM_Port8(0) = ch;
      }
    return(ch);
}