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All the applications that have to answer to the environment in a time-deterministic way and the functionality is complex (need the interaction of mor that one task) should use a RTOS.
for big uP with a lot of RAM and ROM you can easy find payfree RTOS - Linux. A friend of mine makes software for digital cameras and took free file structure, BlueTooth and USB ... it's amazing.
The problem becomes with less RAM and ROM.
For PIC uP the best RTOS is SALVO (www.pumpkininc.com). In the this forum was a link to jCOS (a kind of remade SALVO 2.2 RTOS from some russian guy).
So.. depend on your uP and what you want. In fact, the multitasking is only one of the multiple features, that offers the RTOS. Other features are: delays, timeouts, events, messages, flags, semaphores, counting semaphores, priorities, etc.
Ok My friend this is very BASIC .
Let's start with a OS .a Operating systems is a sort of a manager of electronic RESOURCES .. MEMORY STORAGE .. PERIPHERALS and CPU TIME ..If your particular application or control problem need memory storage.or CPU processing of let's say asignal .You have two options
1)if you only have one task (only one thing to mesure or to control)
then you don't need a realtime OS
2) If you have 2 or more task to control .Then you will have to share the electronics in order to keep the price down.
Share of the memory
Share of the Devices ..LCD ADC ,DAC, com,etc
Share of the CPU
Now ,it's always possible to think the SHARING SCHEME by yourself
but it coul become really complex and more complicated than waht you want to do .
So one solution is to use a off the shelf RTOS .But you have first to uderstand what are issues involved in the selection
I'ts nbo the same to control a $35 dollars drill
than a half a billion dollar robotic arm of a mars explorer
There are trade offs . There is no secret the more powerfiull the RTOS is the bigguer the code is, the slower the code will run .
It' not just a matter of running speed .But very important also is what to do if something not planned occurs how to recover the system. You see my friend so far we're no longuer talking of what you wnt to control or mesure .But what happens if.. if, so you can continue doing what you want to do .. a chip piece of code is ojk for a chip piece of equipment.
how would you like to control the aircraft ailerons with a PIC!
Bon Voyage!
MPU core vendor ARM Ltd. has released an extension to the ARM architecture designed to provide a secure foundation for systems running open operating systems such as Linux, Palm OS, Symbian OS and Windows CE. The company said it created the new TrustZone technology in response to industry demands for greater levels of security in a range of digital electronic devices, such as set-top boxes, next-generation smart phones, and payment and network equipment.
ARM said its TrustZone technology will ensure that data downloaded or run on an ARM device remains secure, protecting consumer privacy and opening up a range of services, such as mobile banking and multimedia entertainment, to wider consumer use.
The technology also complements secure application environments such as Sun Microsystems' Java by making security implementation on devices more efficient, according to ARM.
Users will implement the TrustZone technology within the microprocessor core itself, enabling the protection of on- and off-chip memory. Folding the security elements of the system into the core hardware eliminates security issues surrounding proprietary, nonportable solutions outside the core, the company said.
ARM maintains that making security an intrinsic feature at the heart of every device has minimal impact on the core area or performance, while enabling developers to build cryptography or any other, additional security measures onto a secure hardware foundation.
ARM's TrustZone technology tags and partitions secure code and data within the system and maintains a clear, hardware separation between secure and nonsecure information, said ARM. That separation is said to let secure code and data run alongside an OS securely and efficiently, without being compromised or accessible to attack.
Licensing for TrustZone will begin in 2004, but the specification is available now on www.arm.com.
At avrfreaks there is section for RTOS
some of those works not only with AVR but with many other mcu as well :
**broken link removed**
But not all of RTOPS are listed there
Also this link cac be usefull as well:
**broken link removed**
There are some other post made on RTOS here
Search Mucos Threadx .
There are different RTOS dependent on mcu you use .
Hi... 12 tasks!!! Are you kidding? This will consume almost 2 KB of the ROM memory. Actulally if you make good organization o fthe tasks, you don't need more then 5-7 tasks in most complicated cases.
The lite version has limitation of the tasks to 3 and 1 semaphore 1 message. No timeouts allowed.
RTOS is real time operating system. The word RT it self say's that, it should be time critical. In other words , time is dead line for the application. Some controll application is a deadly example for RTOS. It should do its operation at any cost and any where. Then only we can call that system as Real Time Operating System.
Regards
NVP
The real time OS are preemptive systems. This mean that you have many CPU (ABSTRACTION) working together with each task created. For do this the hardware processor is switching through interrupts. In each interrupt the task enviroment is saved and the next task to run is loaded with the respective enviroment. The process to do this is called task switching. Each task has an assigned time. This time is the interrupt time.
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