How to print float value with printf in TrueStudio ?

I don't know TrueStudio in detail, but I suspect their printf implementation does not support float/double arguments and formatting.

This is quite common, to keep code sizes small. You can check the documentation, or the source code, if available.

Have you tried to add 

-u _printf_float to your linker flags?

my linker option is as follows.

-mthumb -mcpu=cortex-m3 -T'../STM32F103RF_FLASH.ld' -specs=nosys.specs -static '-Wl,-Map=${BuildArtifactFileBaseName}.map' -Wl,--gc-sections -Wl,--defsym=malloc_getpagesize_P=0x80 -Wl,--start-group -lc -lm -Wl,--end-group -specs=nano.specs

would you let me know how to add -u __printf_float to linker option ?

I want use sprintf for float with STM32H7. If I use Newlib-nano unter C/C++ Build -> Settings-> ToolSetting -> General it works with integer and without float. With Newlib standard I get an error in startup-script at Line 10.

"Failure at line: 10 in 'Target Software startup Skript'. Please edit the debug configuration settings.

Error writing data to flash"

With "-u __printf_float" in C-Linker->Miscellaneous->Other options with Newlib-nano I get the same error.

# Set flash parallelism mode to 32, 16, or 8 bit when using STM32 F2/F4 microcontrollers
# 2=32 bit, 1=16 bit and 0=8 bit parallelism mode
# monitor flash set_parallelism_mode 2
 
# Set character encoding
set host-charset CP1252
set target-charset CP1252
 
# Load the program executable
 load		
 
# Enable Debug connection in low power modes (DBGMCU->CR)
set *0xE0042004 = (*0xE0042004) | 0x7
 
# Set a breakpoint at main().
tbreak main
 
# Reset to known state
monitor reset
 
# Run to the breakpoint.
continue

If there are forces to step away from the general path.

https://bitbucket.org/AVI-crak/sprint/src/default/

It seem to be a general problem with sprintf https://www.mikrocontroller.net/topic/359573

May be it is a problem with _sbrk in syscall.c

My solution:

http://chibios.sourceforge.net/html/chprintf_8c_source.html

in TrueSTUDIO:

Project -> C / C ++ Build -> Settings -> Tool settings -> C Linker -> Miscellaneous -> Other options:

• -u _printf_float

assuming newlib-nano as used by CubeMX.

Hi All,

I'm working with last atollic version 9.1.0 and I used your solution (@Hae Ryon Jung​) , and it doesn't work well.

I have a program to read, every second, ADC and converts counts to voltage, the source works well (the values are good) but the text in serial com only is printed well the first time, the others the dot "." is not printed..., I give you an example:

[0]ADC 2754 2.22 V

[1]ADC 2744 221 V

[2]ADC 2745 221 V

adcVal = HAL_ADC_GetValue(&hadc1);
adcRes = adcVal*3.3/4096;
sprintf(buffTmp, "[%d]ADC %d %4.2f V\n\r", (int) counter, (int)adcVal, adcRes);

Thanks for your support

Jordi