Post by thread:FreeRTOS port to PIC18LF45K22 anyone?

Sorry for cross posting here and also on the FreeRTOS forum, but maybe here I'll get more responses. 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. The code will be contributed to the community. What I've found so far: *) In the "standard FreeRTOS download": PIC18_MPLAB which targets a PIC18F452 *) in the community contributions: interactive.freertos.org/entries/304854-freertos-ported-to-pic18f4520 which targets the PIC18F4520 *) in the community contributions: http://interactive.freertos.org/entries/271252-freertos which targets the PIC18F4520 (did not yet investigate what's the difference between the two) My understanding is, that for the PIC18LF45K22 at least some more tweaking for the memory banks is needed. Please advise. Regards, Robert..."Getting an education was a lot like having a sexual disease. It made you unsuitable to a lot of jobs and you had the urge to pass it on."- A weirdo quoting PTerry My public pgp key is available at: pgp.mit.edu:11371/pks/lookup?op=get&search=0x90320BF1

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 family for such a project. I think someone did "sort of" get it on an 18F. What you need is a simpler scheme using timer interrupt and all the tasks called in turn via semaphores and the main program loop. My approach works for 10F/12F/16F and 18F. It's not an actual OS, but a simple framework. 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 discussed this and I've discussed it with Kyle, the author of current JAL compiler. There is even a "Task" construct in JAL, but it's not much use. Basically the lack of decent configurable stack, abillity to have stack frames and manipulate SP and Stack is the problem

On Wed, Jul 13, 2011 at 8:09 AM, Michael Watterson <spam_OUTmikeTakeThisOuTradioway.org>wrote: > There is a way to do "true" Multitasking on 18F family, Olin has > discussed this and I've discussed it with Kyle, the author of current > JAL compiler. There is even a "Task" construct in JAL, but it's not much > use. > I guess by 'true' multitasking you mean a preemptiv scheduler? > Basically the lack of decent configurable stack, abillity to have stack > frames and manipulate SP and Stack is the problem. > Actually you can read and write the STKPTR but then the hardware stack is very limited, so most people implement the scheduler to save the entire stack for the current task and restore it for the new one - as opposed to configure stack frames for each and every single tasks you have. Tamas >