Em 13/7/2011 04:26, Michael Watterson escreveu:
> Resent with TAG
>
> On 12/07/2011 22:38, Robert Berger wrote:
>> I'm playing with the idea of porting FreeRTOS 7.0.1 to a PIC18LF45K22
>> with MPLAB and friends as my time permits.
>>
>> I know that this architecture is suboptimal for a RTOS, but was
>> wondering if someone has done something similar already or if someone
>> would be interested in a joint porting effort.
>>
> Very sub-optimal. I looked at this. The 16F/18F is not the the right=20
> family for such a project.


Indeed it works very well. It depends on your tick rate. I think that
around 5% of CPU time consumption for 1ms ticks at 10MIPS is good enough.

I created several PIC18 projects with FreeRTOS, some very real-time
intensive and all them worked perfectly.


> I think someone did "sort of" get it on an 18F.
>
> [EDIT: I see it is now working on 18F, good]


For several years now :)


> What you need is a simpler scheme using timer interrupt and all the=20
> tasks called in turn via semaphores and the main program loop. My=20
> approach works for 10F/12F/16F and 18F. It's not an actual OS, but a=20
> simple framework.


This sort of stuff is good also. I use something similar a lot too.

Note: FreeRTOS offers co-routines also.


> Introduction
> http://www.techtir.ie/node/1003432
>
> Article
> http://www.techtir.ie/software/jal/multitasking
>
> comments
> http://www.techtir.ie/node/1003431
>
>
> FreeRTOS is good project. But not the way to go for 18F.
>
> There is a way to do "true" Multitasking on 18F family, Olin has=20
> discussed this and I've discussed it with Kyle, the author of current=20
> JAL compiler. There is even a "Task" construct in JAL, but it's not much=
=20
> use.
>
> Basically the lack of decent configurable stack, abillity to have stack=20
> frames and manipulate SP and Stack is the problem.

--=20
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