Em 1/3/2010 08:11, Matt Rhys-Roberts escreveu:
> I'm using printf() to talk directly to EUSART1, without going via the =

> usart.h library. We decided to avoid this library for now in order to =

> keep code as direct and simple as possible.
>
> printf() appears to call code in file =

> c:\MCC18\src\pmc_common\USART\_usartpc.asm , which clears SPBRG when =

> first run, causing serial timing to fail. However, if I manually re-set =

> SPBRG in the watch window, it remains uncleared and serial transmission =

> continues happily.
>
> Q1) Any idea why this has to happen, and what could/should be done about =
it?
> Q2) Does anyone have any optimal examples of setting up printf() =

> explicitly without using usart.h ?
>
> Many thanks,
> Matt
>
> ----------------- code follows -------------------------------
>
> #include <p18F8627.h>
> #include <stdio.h>
> #include <delays.h>
> // #include <usart.h>
>
>
> void main(void)
> {
>
> // config usart, 9600 8n1, Fosc=3D18.432MHz
>
> //     MOVLW    b'01000001'
> //    MOVWF    TXSTA1,A
> TXSTA1 =3D 0b01000001 ;
>
> //    MOVLW    b'11000000'
> //    MOVWF    RCSTA1,A
> RCSTA1 =3D 0b11000000 ;
>
> //    MOVLW    b'00000000'
> //    MOVWF    BAUDCON1,A
> BAUDCON1 =3D 0b00000000 ;
>
> //    CLRF    SPBRGH1,A
> SPBRGH1 =3D 0 ;
>
> //    MOVLW    d'29'
> //    MOVWF    SPBRG1,A
> SPBRG1 =3D 29 ;
>
>
>
> while(1)
> {
> printf ("Hello World!\n");
> Delay10KTCYx (0);
>
> }
>
>
> }
>   =



Why don't you copy this file, modify the copy (remove the SPBRG
clearing) and add the copy to your project? A file that is added
directly to the project has precedence over the library functions.

Best regards,

Isaac

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