Arduino Due, how to direct stdio to USART0 or USART1

[riscy00]

Hi

Arduino Due with SAM3X (Cortex M3), I could not find material that advise how to configure commands from STDIO.h to redirect serial message stream to specfic port, for example printf("Hello World!\n) to USART0 or USART1.....

[westfw]

I believe that Due uses newlib, so the following should work.  (I haven't actually tried it on a Due (I don't have one), but it works for Energia Stellaris platforms. See this thread: http://forum.43oh.com/topic/8308-yet-again-another-boring-question-about-energia-printf/ )

Code: [Select]

ssize_t myWrite(void *cookie, const char *buf, size_t n)
{
  return Serial.write((uint8_t*)buf, n);
}

cookie_io_functions_t myVectors = { 0, myWrite, 0, 0 };

void setup() {               
  Serial.begin(115200);
  stdout = fopencookie((void *)0, "w", myVectors);
  setlinebuf(stdout);
  printf( "This is an fprintf demo\n");
}
This sucks in the well-known large-ish printf(), and it also sucks in newlib's whole stdio/file/etc implementation, adding a total of about 20k to your sketch binary size.   And it may have weird buffering issues and need an occasional fflush(stdout) call.