Kinetis Software Development KitのトピックRe: printf() with float values

printf() with float values

matthias — Tue, 17 Feb 2015 13:53:59 GMT

Hello,

I am using KSDK 1.1.0 with MQX and Processor Expert. Using printf() usually works fine, but I cannot make printf to print float/double values. For the code

float val = 1.234;

printf("Value = %f unit\n", val);

the output is

Value = f

I guess the reason is because printf() does not support float with the default KSDK settings for MQX, so I added "#define MQX_INCLUDE_FLOATING_POINT_IO 1" to mqx_sdk_config.h but the behavior is still the same.

Any hints what I am doing wrong?

Regards

Matthias

Re: printf() with float values

BlackNight — Tue, 17 Feb 2015 14:29:47 GMT

Hi Matthias,

are you using KDS/GNU libraries? If so, have you added

-u _printf_float

to the linker options?

(see printf() and scanf() with GNU ARM Libraries | MCU on Eclipse).

I hope this helps,

Erich

Re: printf() with float values

matthias — Tue, 17 Feb 2015 14:45:16 GMT

Hello Erich,

thanks for the quick reply. I am using the MQX libraries that are included in KSDK. I have seen your post on mcuoneclipse.com (which helped me many times before :-)) and I have tried -u _printf_float in the linker options without success (I guess this option does not apply for KSDK libraries). I think the problem lies somewhere in the configuration of the KSDK/MQX libraries.

Regards

Matthias

Re: printf() with float values

matthias — Tue, 17 Feb 2015 16:00:52 GMT

I found a soultion now, but I am not very comfortable with it yet:

In the KSDK source code, there is a file "std_prv.h" where STD_FP_IO is defined. Setting this define to "1", printf() works with float. But as said, I am not comfortable with changing a file in the KSDK source code.

Re: Re: printf() with float values

DavidS — Tue, 17 Feb 2015 17:20:04 GMT

Hi Matthias,

I have reproduced your finding and have submitted a trouble ticket to our MQX KSDK team.

Documentation should be updated and we should have a master location to define the STD_FP_IO option/capability.

My workaround...

Change std_prv.h to following:

#ifndef STD_FP_IO		//DES added #ifndef
#define STD_FP_IO 0

#endif

And in the project Properties...add Defined for "STD_FP_IO=1":

Regards,

David

Re: printf() with float values

rogerchaplin — Sun, 31 May 2015 23:20:08 GMT

Just thought I'd add my $0.02 worth for anybody else in this situation. I'm using KSDK 1.2.0 with Processor Expert in KDS 3.0 to create code to be built with IAR Embedded Workbench. I've added the MQX component to my project and chosen the standard MQX instead of MQX Lite. I found that the right place to put the define for STD_FP_IO = 1 is in the Component Inspector for MQX, in the User settings Definitions dialog:

Also be sure to make the change to std_prv.h in the KDS project. If you change any of the generated files outside the Processor Expert environment (i.e. you edit them in IAR Workbench) you'll get errors from Processor Expert the next time you try to generate code.

Re: printf() with float values

dorianhildebran — Thu, 10 Sep 2015 14:28:02 GMT

A easyer way is:

Under Project Settings -> C/C++ Build -> Settings -> Tool Settings -> Miscellaneous

enable the Checkbox: "Use float with nano printf".

Re: printf() with float values

syedidris — Thu, 03 Dec 2015 09:16:21 GMT

Hi I am getting same float printing problem in kinetis design studio 3.0.0 how to solve this?

Re: printf() with float values

rajbatra — Thu, 24 Dec 2015 01:08:35 GMT

I just tried this - went to mqx_stdlib_Source/include/std_prv.h and set "#define STD_FP_IO 1" (I'll do the ifndef once this works).

I recompiled the KSDK libraries: mqx_stdlib_frdmk64f, ksdk_mqx_lib, ksdk_platform_lib_K64F12, and mqx_frdmk64f and did a simple printf w/ floating point.

I get MQX_UNHANDLED_INTERRUPT (0x0041) exception.

Setting it back to 0, printf works as expected.

What am I missing?

Thanks,

-Raj

Re: printf() with float values

rajbatra — Mon, 28 Dec 2015 21:43:17 GMT

Silly mistake - I was getting a stack over flow because stack size was set too small for printf floating point support. Once I increased stack, floating point printing worked. FYI, the -u _printf_float made no difference, just Matthias/David's comment to define STD_FP_IO to 1.

Thanks,

-Raj

Re: printf() with float values

eyeow84 — Thu, 24 Nov 2016 02:53:28 GMT

Hi David,

So is it applicable for CW 10.6 with MCU MKE06Z as well? I have posted similar question about printf(%f) at here https://community.nxp.com/thread/438758

Thanks...