Printing Floating point values to fsl_debug_console FRDM-K64F

[michaellyons]

Hello,

I'm using KDS 2.0, KDSK1.1.0, PEx, with the FRDM-K64F.  I'd like to print the Floating point accelerometer values to the terminal using fsl_debug_console.  Strings and integers print fine but it seems debug_printf() doesn't support float.  I also tried

sprintf(str,"%f");

printf("%s",str);

but everything except the floating point val would print.  Is there a compiler setting that must be changed to support floating point printing?

Thanks,

Michael

[likeli · Accepted solution]

Hello Michael,

To print floating point values, you need to enable float/double support to printf() function. In KDS,  please look under: Properties->C/C++ Build->Settings->Tool Settings->Cross ARM C Linker, then add

-u _printf_float to the linker options. It will be OK.

For example, you can write code like this:

float temp=36.5;

printf("\r\n temp=%f \n\r",temp);

[dave408]

I tried adding -u _printf_float to my linker settings for my application, but it didn't work:

Can you please tell me if I've missed something?  Thanks!

[michaellyons]

Hi Dave,

I went to Properties->C/C++ Build->Settings->Cross ARM C Compiler->Miscellaneous then in the "Other compiler flags" box I added "-u_printf_float".  That seemed to work for me.  Are you using KDS, KSDK, and PEx with the FRDM-K64F?

Thanks,

Michael

[dave408]

This is so odd.  Setting the compiler flags didn't work for me, either.  I'm using KDS 2.0, KSDK 1.1, and MQX.  I am not using processor expert.  This is with a K64F.  I just found a post by Erich Styger, so I'll check that out now.  Thank you for your prompt reply!

[michaellyons]

Okay, I haven't tried this with MQX yet so that might be the difference. Screenshot below for help.

If you find the answer please post here.

[dave408]

Ok, I'll definitely post my findings if anyone else presents a solution elsewhere.  Erich's post mentions linker settings as well, not compiler settings.  It also has a lot of detail that I'm not comfortable with, and since it mentioned PEx and not KSDK, I'm not sure it's the right direction for me.  I'll keep digging, and if I can't find the answer, I'll post up a new thread and link to it here.  Thanks!

[matthias]

Hello Dave,

I had a similar problem, so maybe this solution helps: printf() with float values

Regards,

Matthias

[dave408]

Hi Matthias, thank you *so* much for posting a link to your thread!  That was absolutely the problem, and now printf is able to display fp values.  Thanks!!!

[dave408]

Ok, thanks!  That's totally not what Ke had said.  :smileyhappy:  He specifically mentioned the linker, but hey it didn't work and you got it working, so I'll try your suggestion.  Thank you!

[michaellyons]

That worked!  Thank you.