Printf in Keil

[samiassaad]

Posted on March 19, 2011 at 09:36

Printf in Keil

[Andrew Neil]

Posted on May 17, 2011 at 14:28

printf is a standard library function; it is defined by the 'C' standard: it sends its output to stdout - nothing else.

So adding a parameter is not just ''retargetting'' - it is completely changing the standard behaviour! If you want to specify the output destingation in a standard library file, you will have to us fprintf or similar. Or you could redefine stdout between calls. Or create your own function that specifies a destination. Or did you want a function that sends its output to two destinations simultaneously?

[samiassaad]

Posted on May 17, 2011 at 14:28

Yes I want a function that sends its output to two destinations simultaneously, any suggestions ?

[Tesla DeLorean]

Posted on May 17, 2011 at 14:28

Look at how you've hosting the lcd/usart now, and have your ''sendchar()'' function send characters to both.

Or use sprintf() to generate data for both in your own ''DebugPrintf()'' function. #include <stdio.h> #include <rt_misc.h> #pragma import(__use_no_semihosting_swi) struct __FILE { int handle;     /* Add whatever you need here */}; FILE __stdout; extern int sendchar (int ch); int fputc(int ch, FILE *f) {   return (sendchar (ch)); } int ferror(FILE *f) {  /* Your implementation of ferror */   return EOF; } void _ttywrch(int ch) {   sendchar (ch); } void _sys_exit(int return_code) { label:  goto label;  /* endless loop */ }

[Andrew Neil]

Posted on May 17, 2011 at 14:28

''have your 'sendchar()' function send characters to both''

See: 

http://www.keil.com/forum/18511/

(it's for C51, but the principle is the same)

[Tesla DeLorean]

Posted on May 17, 2011 at 14:28

Spooky

[samiassaad]

Posted on May 17, 2011 at 14:28

Thank you Clive

already I know this and I am retarget it to my lcd routine, my question is it possible to retarget it to 2 routinesor more? seial send char, glcd ? Thank you

[Tesla DeLorean]

Posted on May 17, 2011 at 14:28

The point Andrew and I made is that you could do it like this :

int sendchar (int ch) // Hosting function character output routine {      sendchar_usart(ch);     sendchar_lcd(ch);     return(ch); } Why would this NOT work? If your clocks remain busted I could see the USART not outputing at the right baud rate. But that could be fixed by tweaking the baud rate register.

[dannym]

Posted on July 28, 2012 at 07:47

Yeah somebody help me out here.

I'm using Keil and STLink on the STM32F4Discovery board and I see in uVision there's a window for ''Debug (printf) Viewer''.  Which I assume takes printf() and xfers it through the attached STLink I'm debugging with, which sounds great to me!But I use printf() and it jumps to the reset vector.  There's no compile warning about stdout being unimplemented or anything.  What do I need to put in to transfer the data across the STLink?

[dannym]

Posted on July 28, 2012 at 09:01

I've tried following the instructions here:

http://armcortexm.blogs.upv.es/stm32f4-discovery-and-printf-redirection-to-debug-viewer-in-keil/

Yeah the Keil tab I was using was ''STLink (deprecated)'' but just changing to ''STLink Debugger'' led to ''Device Not Found''.  I made all the changes specified up there and the debugger works again.  It doesn't bomb on printf, however, I don't see anything printing out in the printf() Viewer window.