Hi, If you want to use newlib for your FreeRTOS/ARM project, you should have a look at the sbrk function in syscalls.c. There is a range check like: if (heap_end + incr > stack_ptr) return error; and heap_end = & end; Depending on your FreeRTOS heap version the stack pointer shows in your global memory section, normaly the lower RAM. Wheras .end points at the end of your stack, normaly at the end of RAM. So end is alway greater than stack pointer and the memory allocation of newlib fails. So if your printf doesn’t work you maybe look at this one. syscalls.c should be part of your project files. Greets, Joerg

So the heap_3.c allocation would presumably fail?  Thanks for the information. Regards.

Yes I think so, as malloc calls presumably sbrk. I don’t now for sure cause I still use heap_1. Regards