Not able to print(printf) float values in STM32L4/F4

[darla14]

Posted on March 08, 2016 at 09:27

I am using STM32L476RG/F401RE nucleo board and trying to view the output of printf of float value on the terminal I/O.I am using IAR.

But what  I am getting is this : value = %ffor the below code : float value = 168/21617.0printf(''value = %f '' ,value) ;I am already using the semihosting option ticked.Is there any specific setting/condition?It doesn't happens with STM32F29I Disco.Br.Rp #!stm32 #rtfm

[Nesrine M_O]

Posted on March 08, 2016 at 12:18

Hi Rp,

Be sure that you use the right settings: Project>Options>General Options>Print formatter: try to select

Large without multibytes

option The code:

float
value=168/2160;
printf( 
''%f
''
,value) ;

The Output of the terminal I/O: 0.007772 -Syrine-

[AvaTar]

Posted on March 08, 2016 at 13:41

>Be sure that you use the right settings: ...

To be more precise, in ''project options''->''General Options''->''Library options'', ''Printf formatter'', you need to specify ''Large'' of ''Full''. Otherwise, you get no floating point support for the printf() function family.

[connectjagadeep]

Posted on March 08, 2016 at 18:26Could you please let me know the similar settings for AC6 Studio ? I too have difficulty with float value to convert in snprintf function. I use STM32F7Disco. Regards,Jagadeep.

[cbenson]

Posted on March 08, 2016 at 18:45

Also, make sure that your stack pointer is initialized to an address which is a multiple of 8, otherwise a floating point value will not be passed to printf correctly.

[Tesla DeLorean]

Posted on March 08, 2016 at 19:34

Also, make sure that your stack pointer is initialized to an address which is a multiple of 8, otherwise a floating point value will not be passed to printf correctly.

Yeah, I'm pretty sure that's not a hard rule for most Cortex-Mx parts, where 4-byte alignment is workable for LDRD. The Cortex-M0 is the most problematic, where everything needs alignment. The current F7 also doesn't support doubles in hardware.A lot of GNU/GCC platforms have this kind of idiocy in the linker scripts, which is like a goddamn cancer spread all over the place._estack = 0x2002FFFF;    /* end of RAM */

http://www.openstm32.org/Using+CCM+Memory?structure=Documentation

The top of memory would be 0x20030000, the stack pre-decrements.