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CBarb.1
CBarb.1
Associate II
February 26, 2023
Question

I Cannot seem to find a way to do a serial print of a floating number with NUCLEO-C031C6?

  • February 26, 2023
  • 4 replies
  • 1683 views

I am using the NUCLEO-C031C6 dev board and I seem to be having many difficulties. I am trying to do a printf() or use a sprintf() method to print a float number to the serial port. I noticed that this controller device(STM32C031C6T6) does not have an FPU and when I try to enable the linker flag -u_printf_float I automatically get a compilation error: "Nucleo_C031_FirstTest.elf section `.text' will not fit in region `FLASH'

\tools\arm-none-eabi\bin\ld.exe: region `FLASH' overflowed by 8676 bytes

collect2.exe: error: ld returned 1 exit status" I am not sure how to circumvent this? Is there a way to increase the allocation for FLASH? I tried changing the HEAP and STACK sizes but that has no effect. I am sure this device should be able to handle the extra code to do a printf of a float value? Once again any help or suggestions are greatly appreciated. I have attached my project file here

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4 replies

Tesla DeLorean
Tesla DeLorean
Guru
February 26, 2023

It should have 32KB of FLASH, and that should be described in the Linker Script

Floating Point libraries take up space, but I have them in some 16KB parts.

Perhaps it's your other code that is the issue?

Perhaps try the Keil compiler. It has a free license for STM32 CM0(+) parts

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AScha.3
AScha.3
Super User
February 26, 2023

and set optimizer to -Os or -O2 .

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AScha.3
AScha.3
Super User
February 26, 2023

i just tried on F030 : opt. -Os :

(old) prog 7.2kB ;

with float + printf(..float) 11kB overflow.

with float (but no printf float lib) 11.4 kB ;

so you can use float , but for print must put the float in some int by subtract+multiply and put the print chars for float together yourself.

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S.Ma
S.Ma
Principal
February 27, 2023

There are alternative to float for saving code size and core bandwidth.

Here are some example for STM32C03 on STM32C0316-DK just using for example int32_t Temperature_degC_x10 with corresponding custom printf to show like "27.5". There is a printf for the 16x2 LCD and the reporting on Bluetooth Electronics Android app using USART to SPP HC-06 dongle.

Otherwise there is the Q31 fractional bit representation in 32 bit variables elements that was used in the past in mobile phone drivers.

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