How to print float value with printf in TrueStudio ?

[Hae Ryon Jung]

Posted on June 25, 2018 at 07:11

Hi All, 

I'd like to print float value with printf.

when I tried, printf showed blank for float value.

would you please let me know how to set TrueStudio for printing float value with printf ?

I'm using STM32F103RF.

Thanks in advance.

#float

[AvaTar]

Posted on June 25, 2018 at 07:34

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.

[Tobias Wedell]

Posted on June 25, 2018 at 08:06

Have you tried to add 

-u _printf_float to your linker flags?

[Hae Ryon Jung]

Posted on June 25, 2018 at 08:23

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 ?

[Hae Ryon Jung · Accepted solution]

Posted on June 25, 2018 at 09:51

Thanks to you all,

I could print float value by adding '-u _printf_float' as you said.

following captureis project property , add it like this at Settings -> C- Linker -> Command: arm-atolic-eabi-gcc -u _printf_float

[Tobias Wedell]

Posted on June 25, 2018 at 08:39

Sorry can't help you. I'm using Eclipse. 

[AvaTar]

Posted on June 25, 2018 at 08:46

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

The nano-lib version has definitely no printf float support.

[Hae Ryon Jung]

Posted on June 25, 2018 at 09:34

please let me know how to change it, in TrueStudio

[Grisby]

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

[AVI-crak]

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

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