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Angle
Angle
Associate III
December 20, 2022
Solved

how to display the value in float using snprintf?

Hi, how can i use the snprintf for float value in touchgfx? I want to display the data from the sensor in touchgfx lcd but in float

This topic has been closed for replies.
ktrofimo
ktrofimoBest answer
Senior III
December 20, 2022

it also depends on what C library is used. Nano version doesn't have float support. Besides of this TouchGFX requires Unicode strings.

So, I use 

Unicode::snprintfFloat(buffer, bufSize, "%f", var );

​

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12 replies

gbm
gbm
Super User
December 20, 2022

And why don't you check snprintf() in C standard library reference? There are no mysteries - just read the documents. Print formats are common fo all *printf functions. To use floating point formats you must enable float printf library support as suggested by the compiler - look at the compiler messages when using the %f format for the first time.

My STM32 stuff on github - compact USB device stack and more: https://github.com/gbm-ii/gbmUSBdevice
ktrofimo
ktrofimoBest answer
Senior III
December 20, 2022

it also depends on what C library is used. Nano version doesn't have float support. Besides of this TouchGFX requires Unicode strings.

So, I use 

Unicode::snprintfFloat(buffer, bufSize, "%f", var );

​

    Angle
    AngleAuthor
    Associate III
    December 20, 2022

    i have tried it before but its display % instead of float number from the sensor

    KiptonM
    KiptonM
    Senior III
    December 21, 2022

    They are telling you to do this:

    Project->Properties->C/C++ Build->Settings->Tool Settings(Tab)->MCU Settings

    Then check the box that says Use float with printf from newlib-nano (-u _printf_float)

    Yoann KLEIN
    Yoann KLEIN
    ST Employee
    January 2, 2023

    Hello @Angle​ ,

    I just tried it with snprintfFloat and it works. Also, it is specified in the documentation that snprintf only works with %c (element type: char), %s (element type: null-terminated UnicodeChar list), %u, %i, %d, %o, %x formats.

    Please let us know if that solved your issue.

    /Yoann

    Yoann KLEINST Software Developer | TouchGFX
    Angle
    AngleAuthor
    Associate III
    January 12, 2023

    hi, so I need to convert floating-point to char first right? let say I have value -1.23, so I need to convert one by one right? can I get any example or where to refer on how to convert it ?

    Yoann KLEIN
    Yoann KLEIN
    ST Employee
    January 12, 2023

    Hello,

    If you use snprintfFloat you don't have to convert anything, it will work with your float value.

    /Yoann

    Yoann KLEINST Software Developer | TouchGFX
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