topic Re: sprintf with float specifier - how to make it work? in Kinetis Microcontrollers

sprintf with float specifier - how to make it work?

blsousan — Wed, 15 Jun 2016 14:35:29 GMT

I'm using KDS 3.2.0 with the MKE02Z64VLC4 processor and need to use the sprintf/snprintf functions with the float specifier %f. However, it will not work. It shows nothing. I some other posts that have work-around suggestions and various things to try. I just want to know what is the correct/recommended way of enabling sprintf/snprintf to use floating point data types for the format specifier.

Thanks,

Bill

Re: sprintf with float specifier - how to make it work?

BlackNight — Wed, 15 Jun 2016 14:45:18 GMT

Hi Bill,

have you added

-u _printf_float

See https://mcuoneclipse.com/2014/07/11/printf-and-scanf-with-gnu-arm-libraries/

I hope this helps,

Erich

Re: sprintf with float specifier - how to make it work?

blsousan — Wed, 15 Jun 2016 19:44:09 GMT

That worked - but I had to add it as (add the equal sign):

-u=_printf_float

And then select the checkbox in the linker options to adding support for float in printf.

Thanks!

Re: sprintf with float specifier - how to make it work?

williamcarlisle — Wed, 15 Jul 2020 13:43:23 GMT

I am also having this problem, my program crashes on the first sprintf that uses a double argument.

I have checked the box "Use float with nano printf(-u _printf_float)", and it behaves the same way.

I am using MK61FN1M0VMJ12 on KDS 3.2.

This is after the program working great with no issues on Codewarrior.

So I am in the same boat as others, running out of ideas to fix this.

Re: sprintf with float specifier - how to make it work?

ErichStyger — Wed, 15 Jul 2020 15:18:57 GMT

If it is crashing: can you increase the heap and stack size? printf() uses more stack and potentially heap memory (depending on the library).

Re: sprintf with float specifier - how to make it work?

williamcarlisle — Mon, 27 Jul 2020 15:51:39 GMT

I am having trouble finding a define for the heap, I used this thread for assistance.

Changing Heap and Stack Size for NXP Kinetis SDK V2.0 gcc Projects | MCU on Eclipse

The linker file has nothing mentioning the heap.

Using the MQX Stack Usage view in KDS, it appears that none of my tasks are running over. This is pretty quick upon startup, so there are only a few tasks running at the point it crashes.

Re: sprintf with float specifier - how to make it work?

williamcarlisle — Mon, 27 Jul 2020 17:40:56 GMT

Some more info - This is what shows in the console when the system crashes on the sprintf with a float.

BusFault: An imprecise (asynchronous) data access error has occurred.
HardFault: A fault has been escalated to a hard fault.

Re: sprintf with float specifier - how to make it work?

williamcarlisle — Mon, 21 Sep 2020 21:51:10 GMT

This is still not working for me, and after an exhaustive search I have found no solution to get this working.