RAM 6.0 BUX II Series Guía de usuario descargar pdf (Pagina 71)

3 Porting a BSP to Custom Hardware

3.2 Getting a Minimal Kernel Running

Console Output Routines

In addition to the LED routines described above, it may also be helpful to have a

polled-mode serial output routine. The first step in producing this routine is to

create a more basic routine, possibly called something such as outConsole( ), that

does unformatted polled-mode serial output. This does not allow numbers to be

displayed easily, but it does allow diagnostic output. The prototype of

outConsole( ) is as follows:

STATUS outConsole

(

char *buffer, /* buffer passed to routine */

int nchars, /* length of buffer */

int outarg /* arbitrary arg passed from fmt routine */

)

This routine disables all interrupts; use polled mode output for the serial device

until all characters have been printed, then reset the interrupt mask to the previous

value.

Once the outConsole( ) routine is created with the prototype specified above, it is

possible to create a kprintf( ) routine to allow formatted output. The source code

is similar to the following:

int kprintf

(

const char * fmt, /* format string to write */

... /* optional arguments to format string */

)

{

va_list vaList; /* traverses argument list */

int nChars;

va_start (vaList, fmt);

nChars = fioFormatV (fmt, vaList, outConsole, 1);

va_end (vaList);

return (nChars);

}

NOTE: This suggested source code for kprintf( ) assumes that formatted I/O is

configured into the system. However, this may not be the case for your system.

When you are ready to finalize your BSP, the kprintf( ) routine should be

surrounded by #ifdef INCLUDE_STDIO and #endif /* INCLUDE_STDIO */

statements to avoid pulling in the formatted I/O module unexpectedly. As an

alternative, you can write a kprintf( ) routine without calling fioFormatV( ).

However, the non-standard I/O implementation requires more development

effort.

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RAM 6.0 BUX II Series Guía de usuario Pagina 71