Clarification: my recommendation "Don't be afraid." was in response to Bahri's statement "But I'm a bit afraid of using one now."

Yes, the learning curve for RTOS's is sometimes steep. For the 8051 specifically, I can say that CMX's RTX51 has a steep learning curve, aggravated somewhat by their (then) poorly written documentation. Salvo, on the other hand, is pretty easy to learn. Regardless of the product, you've got to come up to speed on it. But then an alternative to the RTOS may be a bunch of concurrent state machines. If one isn't familiar with concurrent state machine design, then that's something that must be learned also.

In any case, Bahri can at least judge whether an RTOS makes sense for the application by examining the manual and playing with the tutorial projects without cost -- other than time, but that's free ;-)

Regards,

--Dan Henry