fputc() is high level "user facing" function, _write() is the "character device" low level implementation. The classic fputc()/fwrite() on PC/UNIX boxes has buffering so as to optimize the transfer to the drivers, and not block on every call.
ST has used __io_putchar() to touch the hardware, but if you want to support multiple USART, for example, this would be more readily handled in the syscalls.c or newlib_stubs.c files commonly used in embedded GNU/GCC implementations.
/*
write
Write a character to a file. `libc' subroutines will use this system routine for output to all files, including stdout
Returns -1 on error or number of bytes sent
*/
int _write(int file, char *ptr, int len) {
int n;
switch (file) {
case STDOUT_FILENO: /*stdout*/
case STDERR_FILENO: /* stderr */
for (n = 0; n < len; n++) {
__io_putchar(*ptr++);
}
break;
default:
errno = EBADF;
return -1;
}
return len;
}
In Keil, I'd use fputc(), but that's something where embedded platforms were the first thought, rather than the last. Again there would be the place you could use a FILE structure of your own, and implement multiple streams.
