Hello,
what is the right implementation for the UART driver read function
(console_fns .deviceRead)? It seems to be implemented differently from
target to target. Some implementations return -1 if the receive FIFO is
empty and some implementations do a busy waiting for new characters.
I would like to use some Posix application code, which switches stdin
into non-blocking mode and uses getchar() to read from UART. getchar()
shall return EOF if no character is available.
This code requires that the UART driver read function does not block,
otherwise getchar() will block. But a non-blocking UART driver is not
sufficient. The function __srefill_r() in newlib/libc/stdio/refill.c
sets the flag __SEOF whenever the driver's read function returns no
characters. So on subsequent calls of getchar() and hence __srefill_r()
the UART driver's read function is not called anymore, because __SEOF
flag is set (see if statement at beginning of __srefill_r()).
My current work-around is to call clearerr(stdin) before calling
getchar(). clearerr() resets the flag __SEOF, so getchar() will get the
current character from the UART driver.
There are many other functions and modules (e.g. console*.c,
rtems_termios*, ...) involved between getchar() and the UART driver's
read function. So it's a little bit hard to dig into that issue and to
find a good solution.
Best regards,
Daniel Krüger
--
SYS TEC electronic GmbH
Am Windrad 2
08468 Heinsdorfergrund
Telefon : +49 (0) 3765 38600-0
Fax : +49 (0) 3765 38600-4100
Email : daniel.krue...@systec-electronic.com
Website : http://www.systec-electronic.com
Managing Director : Dipl.-Phys. Siegmar Schmidt
Commercial registry : Amtsgericht Chemnitz, HRB 28082
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