Lpc2000

--- In lpc2000@yahoogroups.com, "tiogate" <gate@t...> wrote:
> 
> Hello, gentlemen,
> 
>    I am experiencing something that does not make sense to me. To 
> make my debugging easier I wish to use the printf function to send 
> formatted output to UARTO. 
> 
>    Fine. As far as I can see, I did everything right: I rewrote the 
> putchar function so it writes to UART0, and the putchar function 
> works OK. 
> 
>    However, when I use the printf function, it does not output to 
> UART0 (if it outputs to something at all), and I can't understand 
> why not.
> 
>    Checking the .MAP file, I see the compiler takes the putchar 
> function that is in my main.o and the remaining functions that 
> printf uses (such as puts, fflush, etc) it takes from libc.a .
> 
>    If I DO NOT write my putchar, I see from the .MAP file that the 
> compiler takes putchar.o from libc.a -- and then I understand why 
it 
> wouldn't send anything to the UART0. But why doesn't printf send to 
> the UART0 if my putchar function tells it to?
> 
> Hoping for some enlightening from you gurus,
> 
> Fernando

All depends on what c library you are using, with  newlib you need to 
override _write or _write_r (reentrant version) eg.

int _write_r(void *reent, int fd, char *ptr, size_t len)
{
   // send data via uart
   UART_DataSend( UART0, ptr, len );
   return len;
}

unlike other c libs newlib does not use putchar.
Look in the newlib docs for other system overdides.

Regards
Spen