I just want use an OS because, a single task you're doing is seperated to multiple parts if you do not use an OS.

Say I'm driving an output till an input becomes high; and then I wait in that condition for 2 seconds. After the timeout I do something else.

Without and OS, I need to use the timer interrupt to do the job after timeout. And if I have 2 threads doing similar operations, the timer part will be more complicated.

Beyond this kind of operations, I also manage the user interface. It is much simpler if you program it in sequential way and blocked waiting some input. If I do not use an OS, I need to perform the same task in a distributed way, which seems a bit complicated.

Based on these, I was thinking that using an OS is simpler an was wondering the processing overhead and delay caused by using an OS.

I was planning to use a simple os which provides basic cooperative task scheduling and some sort of sync. and messaging mechanisms.

But I'm a bit afraid of using one now.

:)