Cannot use printf with floats on a Cube generated System Workbench project for STM32F429i discovery board.

See: http://www.nadler.com/embedded/newlibAndFreeRTOS.html

If you're using an RTOS, probably your printf with %f is failing because printf internally tries to malloc a buffer and fails.

Let us know if that's the issue please!

When I had issues with snprintf() under FreeRTOS, I increased heap and stack allocation as well as task stack size (by a factor of 10x from the original size), and the issue was resolved.

@davidregan9​ - Was this any help? Did you get your issue fixed? Please let us know,

Thanks, Best Regards, Dave

Hi Dave

I am still having issues.

I tested the return values of the printf which was a positive value (albeit wrong).

No errno was set.

I have been trying to isolate the issue. Without RTOS it works

BTW Increasing heap/stack made no difference.

@davidregan9​ - Can you confirm you are using:

• FreeRTOS?
• newlib and gcc?

If yes to both, your problem will definitely be solved using code here: http://www.nadler.com/embedded/newlibAndFreeRTOS.html

Please let us know, Thanks, Best Regards, Dave

@Dave Nadler​ I am using FreeRTOS 10.2.1; GCC ARM Embedded Toolchain 8 2019-q3-update and newlib (I assume since I removed -specs=nano.specs)

@davidregan9​ You are using newlib (or newlib-nano).

Use the code/instructions on my web page and it will solve your problem.

If the page isn't clear PLEASE let me know how to improve it.

Thanks, Best Regards, Dave

@Dave Nadler​ I will try it out and let you know. Thank you

@Dave Nadler​ 

Hello Dave. I implemented your solution with heap_useNewlib.c and it worked.

If I'm understanding it correctly ANY kind of dynamic memory assignment is now coming out of the RAM between end and _estack.

That's all printf family type stuff and all RTOS tasks/objects.

Have you had any experience of running out of heap in a reasonable sized project. On our last project we had an external sdram and directed all RTOS activity to that.