Trouble with printf and sprintf with float in STM32Cube + VS Code (CMake)

[umut373]

Hi everyone,

I'm working on an STM32 (Nucleo-F446RE to be spesific) project using the STM32Cube extension for VS Code, not CubeIDE. I'm using CMake for building the project.

I encountered a few issues:

1. printf doesn't print anything to the serial monitor, so I switched to using HAL_UART_Transmit.

2. When I try to print a float using sprintf(msg, "value: %f\n", var);, it doesn’t work. The output just skips the float value (e.g., "value: \n").

3. After some research, I found out I need to add "-u _printf_float" to the linker flags to enable float formatting support with printf and sprintf.
   However, I'm new to CMake and I couldn’t figure out which CMake file I need to modify in the project folder to add this flag.

I'd really appreciate it if someone could guide me:

• Where exactly should I add the "-u _printf_float" flag?

• Is there anything else I should do to make printf work properly over UART?

Thanks in advance for your help.

[Andrew Neil]

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@umut373 wrote:

1. printf doesn't print anything to the serial monitor

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Have you followed the instructions:

https://community.st.com/t5/stm32-mcus/how-to-redirect-the-printf-function-to-a-uart-for-debug-messages/ta-p/49865