Kinetis Software Development KitのトピックRe: Issues with freeRTOS tickless on K21

Issues with freeRTOS tickless on K21

martis — Fri, 25 Nov 2016 11:28:22 GMT

I am using freertos in my application, and I am now trying to lower the power consumption by implementing tickless mode.

However, I have some issues regarding the implementation of vPortSuppressTicksAndSleep.

I used the freertos_tickless_twrk21f120m project from SDK_2.0_TWR-K21F120M as a starting point. As it is, the example seems to be working, but when starting to modify it and test other frequencies, it does not behave as expected.

The LPTMR is setup with the default config which means 1khz clock.
However, configLPTMR_RATE_HZ is set to SystemCoreClock, which is 120000000.
When calculating the amount of LPTMR counts for one tick, the following expression is used:

ulLPTimerCountsForOneTick = configSYSTICK_CLOCK_HZ / configLPTMR_RATE_HZ;

As these two are defined to be the same, ulLPTimerCountsForOneTick is one. In the example both configTICK_RATE_HZ and configLPTMR_RATE_HZ is 1000, which means that it is correct that one tick is 1 tick on the LPtimer.
But for the general case, the calculation doesn't make any sense, as the it doesn't include anything about the tick rate.

The correct calculation should be:
ulLPTimerCountsForOneTick = configLPTMR_RATE_HZ / configTICK_RATE_HZ;

Fixing this issue allows me to play with different frequency settings of the LPTimer and RTOStick, and the timing looks correct.
But this is only until the sleep period is interrupted by an external interrupt, which sometimes causes the project to hang. This is due to the
vTaskStepTick( ulCompleteTickPeriods );
which is called with
ulCompleteTickPeriods = LPTMR_GetCurrentTimerCount(TICKLESS_LPTMR_BASE_PTR);
as parameter.

This again assumes that the LPTMR is at the same frequency as the rtos tick.

Adding:
ulCompleteTickPeriods /= ulLPTimerCountsForOneTick;
after reading out the value scales the value correctly, and avoids getting caught in the configASSERT in vTaskStepTick due to wrong input.

I do not know if there are any more errors in this implementation, so it would be great if someone could have a look at this.

Re: Issues with freeRTOS tickless on K21

soledad — Wed, 30 Nov 2016 17:32:49 GMT

Hi,

Just wanted to let you know that I’m already working on your issue.I will get back to you know as soon as possible.

Have a great day,

Soledad

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Re: Issues with freeRTOS tickless on K21

soledad — Fri, 02 Dec 2016 00:02:57 GMT

Hello,

You are right, we already were able to reproduced the problem, and we need to escalate to our development team, once we have an update from them I will contact you asap

Have a great day,
Sol

Re: Issues with freeRTOS tickless on K21

martis — Mon, 05 Dec 2016 09:24:26 GMT

Glad to see that you are looking into it.

Looking forward to hearing the conclusion!

Re: Issues with freeRTOS tickless on K21

martis — Wed, 07 Dec 2016 11:30:05 GMT

Any news on this?

Re: Issues with freeRTOS tickless on K21

2bluesc — Thu, 05 Jan 2017 02:40:41 GMT

Any updates? I'm running to the same problem on the Cortex-M0 port.

Re: Issues with freeRTOS tickless on K21

javiercardona — Thu, 05 Jan 2017 06:58:27 GMT

I also happen to have the same problem on the Cortex-M0 (KL27).

Re: Issues with freeRTOS tickless on K21

soledad — Wed, 11 Jan 2017 23:24:35 GMT

Hi martis,

Our development team reproduced and fixed the issue. Thank you for your feedback. Please check the comments below:

"Issue was reproduced and fixed. I have used configLPTMR_CLOCK_HZ instead configLPTMR_RATE_HZ. Macro configLPTMR_RATE_HZ defined as (configCPU_CLOCK_HZ) was wrong. LPTMR is not driven by CPU clock (120MHz) but by LPO (1kHz). New macro configLPTMR_CLOCK_HZ is defined according to real LPTMR clock frequency 1kHz.

There is issue with configLPTMR_CLOCK_HZ definition in FreeRTOSConfig.h. LPTMR is not initialized in FreeRTOS but in application, but LPTMR is used in freertos source code. That is also reason why we need to define LPTMR clock frequency somewhere (currently in FreeRTOSConfig.h). This is pointing out to problem with lptmr tickless implementation. LPTMR tickless should be implemented as part of application, not as part of FreeRTOS."

Have a great day,
Sol

Re: Issues with freeRTOS tickless on K21

martis — Thu, 12 Jan 2017 07:41:11 GMT

Hello Sol,

Thanks for finally getting some feedback on this.

It is not clear to me in this written explanation exactly what changes the development team has done in the "port.c" file. Could you please provide the fixed "port.c"?

I am also not sure what is ment with "There is issue with configLPTMR_CLOCK_HZ definition in FreeRTOSConfig.h. LPTMR is not initialized in FreeRTOS but in application, but LPTMR is used in freertos source code".

Yes, configLPTMR_CLOCK_HZ must be added to FreeRTOSConfig.h and the LPTMR must be initialized by the application, but so does configCPU_CLOCK_HZ and the system clock. FreeRTOS does depend upon the application setting some parameters and configuring this correctly according to this, but I don't think this is a problem.

It would be really great to get a quick reply with the fixed "port.c", because it has been more than 1,5 months to get an answer here, and I would like to be able to continue my development.

Thanks!

Re: Issues with freeRTOS tickless on K21

martis — Tue, 17 Jan 2017 08:02:37 GMT

I still need the fixed port.c.

Could you please provide this soon?

Re: Issues with freeRTOS tickless on K21

gsmgbl — Wed, 18 Jan 2017 22:24:37 GMT

Hi Sol,

I have similar situation with KL27 and i am using freertos v8.2.3, I found no definition about the LPTMR for both clock or rate macros. Would it be possible to post a example project (fixed freertos_tickless project), then we can see more clearly how it works? as well as the fixed port.c file is a great help.

Thank you and greatly appreciate this!!

Regards,

Gilbert

Re: Issues with freeRTOS tickless on K21

BlackNight — Thu, 19 Jan 2017 20:28:54 GMT

I have a project for the FRDM-KL27Z with KDS, Kinetis SDK V2.0 and FreeRTOS with tickless idle mode and low power timer on GitHub here: mcuoneclipse/Examples/KDS/FRDM-KL27Z/FRDM-KL27Z_McuOnEclipseLib at master · ErichStyger/mcuoneclipse · GitHub

You find the FreeRTOS (I'm using the latest V9.0.0 with support for static allocation and trace) in the root of that project. The port is for many Cortex, so you can use it e.g. for M0+, M4(F) and as well for M7, although I have used the low power timer only with Kinetis-L. Unlike the port in the SDK, I'm using either Systick OR LPTMR and not mixing them (which does not make sense in my view).

I hope this helps,

Erich

PS: That project is using Processor Expert in the background (I have found a way to use it with the SDK V2.0) with include header files for configuration (see McuOnEclipse Components: 12-Dec-2016 Release | MCU on Eclipse ): If you don't want/need a graphical user interface to configure FreeRTOS (and the other components), simply remove that .pe file in the project root.

Re: Issues with freeRTOS tickless on K21

gsmgbl — Thu, 19 Jan 2017 22:43:22 GMT

Hi Erich,

I am using IAR Workbench for my development unfortunately, I took a look at your project and looks quite different from my environment. So do you have any similar project under IAR? or can you give me some hints or directions to convert the project? cos this is my first project. Thanks a lot and greatly appreciate your help!!

Regards,

Gilbert

Re: Issues with freeRTOS tickless on K21

BlackNight — Fri, 20 Jan 2017 06:36:27 GMT

Yes, this is an Eclipse project, not an IAR project. But the FreeRTOS port supports many different compilers. Have a look at mcuoneclipse/FRTOS1config.h at master · ErichStyger/mcuoneclipse · GitHub and the configCOMPILER macro: you can set this to configCOMPILER_ARM_IAR and then the FreeRTOS is configured to use IAR compiler.

I hope this helps,

Erich

Re: Issues with freeRTOS tickless on K21

soledad — Mon, 23 Jan 2017 18:10:29 GMT

Hi,

Developers are preparing the patch. I'll let you know as soon as they have it ready.

Regards

Sol

Re: Issues with freeRTOS tickless on K21

gsmgbl — Tue, 24 Jan 2017 17:41:24 GMT

Hi Sol,

I re-generated the example project from the MCUExpress due to the new 2.1 SDK and FreeRTOS V9.0.0. I found that the configLPTMR_CLOCK_HZ are still using the configCPU_CLOCK_HZ, which mentioned it is wrong previously. So is the patch for the FreeRTOS V8.2.3 or V9.0.0 or both? Please advise. Thank you.

Regards,

Gilbert

Re: Issues with freeRTOS tickless on K21

davidjurajda — Thu, 26 Jan 2017 13:06:01 GMT

Hello Everybody,

I would like to share fix for discussed issue.

There are two FreeRTOS versions (8.2.3 and 9.0.0) available in distribution system (mcuxpresso.nxp.com).

Version depends on the release in which specific board become supported.

Each version have slightly different code organization for low power tickless idle mode.

I have prepared patch with following updates:

---- v. 8.2.3. ----

boards\<board>\rtos_examples\freertos_tickless\FreeRTOSConfig.h

original: #define configLPTMR_RATE_HZ (configCPU_CLOCK_HZ)

fixed: #define configLPTMR_CLOCK_HZ (1000)

freertos_8.2.3\Source\portable\<tool>\<architecture>\port.c:

vPortSuppressTicksAndSleep()

original: ulCompleteTickPeriods = LPTMR_GetCurrentTimerCount(TICKLESS_LPTMR_BASE_PTR);

fixed: ulCompleteTickPeriods = LPTMR_GetCurrentTimerCount(TICKLESS_LPTMR_BASE_PTR)/ulLPTimerCountsForOneTick;

prvSetupTimerInterrupt()

original: ulLPTimerCountsForOneTick = configSYSTICK_CLOCK_HZ / configLPTMR_RATE_HZ;

fixed: ulLPTimerCountsForOneTick = ( configLPTMR_CLOCK_HZ / configTICK_RATE_HZ );

---- v. 9.0.0. ----

boards\<board>\rtos_examples\freertos_tickless\FreeRTOSConfig.h

original: #define configLPTMR_RATE_HZ (configCPU_CLOCK_HZ)

fixed: #define configLPTMR_CLOCK_HZ (1000)

freertos_9.0.0\Source\portable\<tool>\<architecture>\fsl_tickless_lptmr.c

vPortSuppressTicksAndSleep()

original: ulCompleteTickPeriods = LPTMR_GetCurrentTimerCount(pxLptmrBase);

fixed: ulCompleteTickPeriods = LPTMR_GetCurrentTimerCount(pxLptmrBase)/ulLPTimerCountsForOneTick;

prvSetupTimerInterrupt(

original: ulLPTimerCountsForOneTick = configSYSTICK_CLOCK_HZ / configLPTMR_RATE_HZ;

fixed: ulLPTimerCountsForOneTick = ( configLPTMR_CLOCK_HZ / configTICK_RATE_HZ );

I would like to explain configLPTMR_CLOCK_HZ macro, because it is confusing. Its purpose is to pass low power timer clock frequency to tick functions in FreeRTOS core files.

There is difference in comparison with systick timer (common across different architectures), because systick timer is initialized directly in official port.c (in v 8.2.3 or in fsl_tickless_lptmr.c in 9.0.0) file (prvSetupTimerInterrupt function). The low power timers are different between families (kinetis, lpc) and hence it need to be initialized in application (LPTMR_Init in main). Macro configLPTMR_CLOCK_HZ cannot be changed without update of low power timer initialization in main function (LPTMR_Init). It is not perfect, but it is the reason for existence of configLPTMR_CLOCK_HZ. Current implementation have this inconsistency, and we are going to rework it.

Another topic to explain is split of port.c into several files in v 9.0.0. It is because we are supporting several different low power timers across one architecture (e.g. ARM_CM4F). LPTMR is used in kinetis line, and RTC in LPC line.

I would like to thanks Martis and other people in discussion for reporting the issue. I am sorry for delay in my reaction.

Regards,

David (FreeRTOS integrator)

Re: Issues with freeRTOS tickless on K21

martis — Thu, 26 Jan 2017 13:52:34 GMT

Thanks David, glad to finally get this confirmed :smileyhappy:

Re: Issues with freeRTOS tickless on K21

gsmgbl — Fri, 27 Jan 2017 16:35:11 GMT

Hi Erich,

Thanks for your info and tips.

Greatly appreciate!

Regards,

Gilbert

Re: Issues with freeRTOS tickless on K21

gsmgbl — Fri, 27 Jan 2017 16:54:55 GMT

Hi David,

I am using the V8.2.3 on my IAR and I am a beginner for FreeRTOS and first implementing the low power capability.

My MCU is Kinetis KL7.

First, I measured my board with no tickles idle enabled (#define configUSE_TICKLESS_IDLE 0), then my current consumption is 12mA approx.

Then I enabled (#define configUSE_TICKLESS_IDLE 1), then my current consumption get down to 4mA.

After you posted this patch, then I enabled both the (#define configUSE_TICKLESS_IDLE 1 and #define configSYSTICK_USE_LOW_POWER_TIMER 1) and followed the freertos_tickles project, but it is measured as 4mA and no further power saving.

Did I miss something when I am following the freertos_tickless project?

My target is get down to something close to the VLPR mode, which approx. a few hundred uA.

Do you have any recommendations or tips that guide me on the right path? any example project that I can try out?

Please advise. Thank you!

Regards,

Gilbert