RE: WFI internals

Susheel Nuguru — Tue, 26 May 2015 09:10:00 GMT

I will change the title to suit this question better, i hope it is ok to you.

RE: WFI internals

Susheel Nuguru — Tue, 26 May 2015 09:07:22 GMT

__attribute__((always_inline)) __STATIC_INLINE void __WFI(void)

INLINE does not guarantee that compiler will in all cases inline the function, hence adding __attribute__((always_inline)) forces the compiler to inline this function and the only exception is if the its a recursive inlined function which will exhaust the whole memory. Read this for more information on always_inline attribute

__ASM volatile ("wfi");

wfi is assembly instruction, but we can use it inside C code by giving __ASM keyword, this __ASM keyword tells the compiler to skip compiler stage and hand over this line directly to the assembler. I am not sure what volatile will do here as this is a single instruction.

you do not need to write the rest of the code in assembly, as the above code is accepted by C compiler. There are tons of examples you find if you google "inline assembly in C". Below is one good example I found that might be of your interest. www.codeproject.com/.../Using-Inline-Assembly-in-C-C