[En-Nut-Discussion] Early printf Capability

[Harald Kipp]

GDB on the command line is probably something for
people with a lot of time to create scripts.

After completely failing to setup Eclipse, I tried
Insight again with success (for ARM). Finally I found
out, that GDB will not really help with the optimization
problem (Nut/OS fails when compiled with optimization).

So I get back to the old method of printing out debug
lines. However, Nut/OS fails in a very early stage.

Here's how to setup stdout very early, even before the heap
exists. This sample had been added to arch/arm/dev/at91init.c
(CVS HEAD). Apart from the hardware initialization, an AVR
version will not differ much.



#include <dev/debug.h>
#include <stdio.h>

struct __iobuf {
     int     iob_fd;		/*!< \internal Associated file, device or socket 
descriptor. */
     u_short iob_mode;		/*!< \internal Access mode, see fcntl.h. */
     u_char  iob_flags;		/*!< \internal Status flags. */
     int     iob_unget;		/*!< \internal Unget buffer. */
};

struct __iobuf dbg;

/*!
  * \brief AT91 specific initialization.
  */
void McuInit(void)
{
     /* Set the vector. */
     outr(AIC_SPU, (unsigned int)SpuriousEntry);

     /* Enable UART clock. */
     outr(PS_PCER, _BV(US0_ID));
     /* Disable GPIO on UART tx/rx pins. */
     outr(PIO_PDR, _BV(14) | _BV(15));
     /* Reset UART. */
     outr(US0_CR, US_RSTRX | US_RSTTX | US_RXDIS | US_TXDIS);
     /* Disable all UART interrupts. */
     outr(US0_IDR, 0xFFFFFFFF);
     /* Clear UART counter registers. */
     outr(US0_RCR, 0);
     outr(US0_TCR, 0);
     /* Set UART baud rate generator register. */
     outr(US0_BRGR, 0x28);
     /* Set UART mode to 8 data bits, no parity and 1 stop bit. */
     outr(US0_MR, US_CHMODE_NORMAL | US_CHRL_8 | US_PAR_NO | US_NBSTOP_1);
     /* Enable UART receiver and transmitter. */
     outr(US0_CR, US_RXEN | US_TXEN);

     __iob[1] = &dbg;
     dbg.iob_fd = (int)((uptr_t)(* devDebug0.dev_open) (&devDebug0, "", 0, 0));
}