1.RTOS is a normal program so it must use RAM and program memory of your
microcontroller.

2.RTOS has an important role in time management of embedded system because
our simple program run sequentially command by command from the top to
bottom and then cyclic to the top again (it usually operate like this all the
time you run the program) but if I assume there are some tasks that aren’t
necessay to run often as the main loop run or there are some tasks that require
the certain period of time to run, so if these two conditions correspond to your
program requirement I suggest to use RTOS , it will help you so much (at
least it better than you write the code to handle these situation yourself).
RTOS is not so hard.If you understand its mechanism then it is a fun thing. I
think RTOS is not more difficult than we can learn.

3.The importance of RTOS is depend on the number of features your application
have to do.I will show you an example of temperature data logger that have
features like this…

- Need to store the measurement data into SD-Card.
- Show the measurement data on the color lcd screen.
- Can communicate with PC via USB while datalogger is working to send data to
the program that running on PC and plot the graph.
- It can specify the alarm temperature in real-time by using the touch screen
as the input device to input the temperature.

If you design above datalogger by using only general ISR (Interrupt
Service Routine), maybe you will got stuck and your code will look
cumbersome.The using of RTOS is suitable for handle this kind of datalogger
because RTOS can apply the feature of multitasking for separate the code into
3-4 task such as DAQ_task , UI_task , USB_task etc.Each task has a specific
responsibility and run asynchronously with other tasks.Every task communicate
with each other by using the message such as mailbox , message queue (They
are data structure normally declared as global variable and used for store an
information that each module in the system can obtain and use together).

The name below is open source and non-commercial RTOS that you can use and
modify them to make your embedded project more reliable and powerful.

1.FreeRTOS
2.µC/OS-II Kernel from Micrium
3.FreeOSEK
4.Tnkernel
5.eCos
6.CooCox CoOS
7.TinyOS
8.PICos18
9.AvrX
10.RTEMS

List above is only some examples of popular RTOS but there are hundred or
thousand RTOSes exist in the world.

For more information about RTOS please visit

1.http://www.embedded.com
2.http://www.dedicated-systems.com
3.http://www.eg3.com/report-rtos/index.htm
4.http://www.eg3.com
5.http://www.edaboard.com

Reference site : http://www.electoday.com/bbs/archiver/?tid-1644.html

Thank you,
Admin

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Related posts:

1. RTOS for small embedded system.
2. RTOS for AVR part two
3. RTOS for AVR part one.