what is the real difference?

robot_gary wrote on Sunday, May 04, 2008:

Can anybody here give a detail description of the real difference of using freeRTOS and ucOSII, I want to know the pros and cons, please!


ikbahrian wrote on Sunday, May 04, 2008:

follow the link. Hope fully it helps you.



robot_gary wrote on Monday, May 05, 2008:

but that is not what I want to know, I want to know the difference between FreeRTOS and ucOSII.

neilbradley wrote on Monday, May 05, 2008:

I have extensive experience with uCOS-II and definite familiarity with FreeRTOS. I am not attempting to pass judgement on which is “better” or “worse”. Value judgement on these issues is in the eye of the beholder. Whether or not a bullet point is an issue or not depends upon one’s requirements in an RTOS:


* All threads are their own priority (no round robining on the same priorities)
* Costs ~$5K for a "single end product" or around $25K for a "product family"
* Mature (roughly 15+ years old)
* Other stacks available, like USB and TCP/IP (for fees) and are mature as well
* Timer support
* Event flags support
* Message mailboxes
* Highly configurable (on a per OS API perspective)
* 100+ ports to various CPUs and architectures
* FAA Certified
* Very tiny (can reduce to ~2K and 256 bytes of memory in minimalist configuration

FreeRTOS -

* Almost completely free (modified GPL with exceptions - see the FreeRTOS web site for restrictions)
* Supports different thread priorities and round robining on threads of the same priority
* No timer support
* No event flag support
* Co-routine feature (very useful!)
* Roughly ~25 ports (not sure how many exactly)
* Fairly young (circa 2004)
* Very configurable (on a subsection basis)

I’ve used both in various configurations/applications. I’ve chosen uCOS-II in a couple of instances where FreeRTOS wasn’t sufficient (porting existing code that used event flags, and at the time, lack of counting semaphores). However, starting a new project, I can’t see much (if any) of a reason to consider uCOS-II over FreeRTOS. OS “Overhead” on uCOS-II vs. FreeRTOS is insignificant/unmeasurable on the architectures I’ve worked with both.

robot_gary wrote on Monday, May 05, 2008:


That is a really nice summary, is there more?