SW4STM32 and SW4Linux fully supports the STM32MP1 asymmetric multicore Cortex/A7+M4 MPUs

   With System Workbench for Linux, Embedded Linux on the STM32MP1 family of MPUs from ST was never as simple to build and maintain, even for newcomers in the Linux world. And, if you install System Workbench for Linux in System Workbench for STM32 you can seamlessly develop and debug asymmetric applications running partly on Linux, partly on the Cortex-M4.
You can get more information from the ac6-tools website and download (registration required) various documents highlighting:

System Workbench for STM32

Redirecting printf() does not work



Regarding the ‘#’ characters, its because a sharp as first character of a line is introducing a numbered list item (like a star will introduce an unnumbered, dot, lost); two sharps (or two stars) introduce sublist items and so on...

To avoid that just include your code between {CODE()} and {CODE}, as I’ve done in your message above. (by the way to display special characters or syntax, surround them between ~np~ and ~/np~). You have a quite exhaustive presentation of the Wiki syntax used on this site (which is based on tiki-wiki) at https://doc.tiki.org/Wiki-Syntax+TextQuestion

To come back to your original problem, what you have done should work; are you sure the file in which you define the PUTCHAR_PROTOTYPE function was effectively included in your executable? If it is in a file that is only needed for this function, it may be omitted; try putting this function in your main program for example.

Bernard (Ac6)