float in sprintf

[alireza.r]

hello every one i tried to use sprintf and change a float variable to chars in visual stdio via VisualGDB
like:

float a;
char b[5];

sprinf(b,”%f”,a);

but it make hard fault in micro(stm407), how i can active float variable in sprintf or printf ?

[ket]

Hi,

Please read our STM32F4 tutorial on the topic for hints:
http://visualgdb.com/tutorials/arm/stm32/fpu/

[alireza.r]

thanks for your replay
but my problem is with hardware floating point. if i use software floating point the program run correctly
but when chose hardware floating point the hard fault occur.

Note that -mfloat-abi=hard has been added to GCC flags correctly

i use sprintf(..) and in Disassembly it is vcvt.f64.f32
how can i solved this problem.

[support]

Hi,

This problem means that the standard C library has been compiled in a way that treats the ‘%f’ format in a way that uses the double type. We would recommend simply using an alternative implementation of sprintf() from some open-source library and tweaking it so that it only uses the float type.

[alireza.r]

thanks for your replay bazis

but i have this problem with float variable too.
i readied this link before
http://visualgdb.com/tutorials/arm/stm32/fpu/

and i understood that this problem occre with double type but i just use float not double
and i have this problem.

[support]

Hi,

The problem is that printf() inside itself uses ‘double’. Although you pass a float there, it reads ‘%f’ in your string and somehow converts it to double. You cannot change this behavior by modifying your program as it is located inside the printf() that is a part of the standard library. You could either modify the standard library used by GCC (which is somewhat cumbersome), or simply use another open-source implementation of printf() (there should be plenty of those available online).

[Reza1757]

Hi

I’m using vidualGDB for programming on STM32 microcontroller with visual studio 2019.

When I want to convert float into string with sprintf() function then it seems doesn’t work.

I want puts a buffer array on LCD but when I puts it float variable doesn’t visible…

I saw just characters and no number.

[Reza1757]

Hi

I had this problem and this link was useful.

https://visualgdb.com/tutorials/arm/stm32/fpu/

[Author]

Posts