[ECOS] GDB and console (libc_stdio) on same serial port

[Jonathan Larmour]

George Sosnowski wrote:
> I'm running on an 860T where there's one serial port available which is
> connected to SMC1.
> 
> Is it possible, through some configuration, to have an ecos ram
> application image which has gdb and a console (libc_stdio used as a
> shell with non-blocking i/o /dev/tty0) on a single serial port? 

Well you can leave libc to use the default "/dev/ttydiag" device which 
means the output will be passed to GDB. This is the default anyway.

> I understand that in such a situation when gdb takes over (sees a ctrl-c
> or a $) the i/o to the shell would be in a polling (blocking) mode. It's
> not terribly important to me if the gdb stubs are from redboot or within
> the ecos ram application. Whatever works would be fine. Ideally I have
> redboot load an ecos application ram image automatically from flash and
> run it, and after the ecos ram application is running sometimes I'd like
> to be able to connect to it via gdb serially. However, by default I'd
> like to be able to interact with the ecos ram application through its
> console shell non-blockingly.

Generally, the principle is that a channel is used for GDB or an 
application since you can't be connected through GDB and talking to an 
application at the same time.

> I've tried including the gdb stubs in the ecos ram application, but it
> seems when I run the ecos ram application that gdb is already active in
> this case because I get some $...... output on the serial port in
> response to any serial input. Ideally I'd like to get the behavior of
> redboot where gdb is initially inactive and the redboot shell is active.
> I've also tried to inherit the serial port from redboot (as ttydiag),
> but this seems to give blocking i/o to the ecos ram application console
> shell when doing a getchar().

Indeed.

For what you'd want you'd need to make some tweaks to eCos. I would 
suggest the way to do this is decide how you want to recognise a switch to 
GDB mode (ctrl-c, $, or possibly even some user command you give your 
application) and when you want to switch do:

cyg_hal_user_break( (CYG_ADDRWORD *)hal_saved_interrupt_state );

You'll have to have defined these first:

#include <cyg/hal/hal_arch.h>
#include <cyg/hal/hal_misc.h>
extern struct Hal_SavedRegisters *hal_saved_interrupt_state;

Jifl
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