topic Re: How to wait in Low Power mode with FreeRTOS and Kinetis MKL16Z in Kinetis Software Development Kit

How to wait in Low Power mode with FreeRTOS and Kinetis MKL16Z

bgraham — Wed, 06 Feb 2019 20:14:27 GMT

Kinetis MKL16Z

MCUXpresso IDE v10.2.1 [Build 795] [2018-07-25]

Amazon FreeRTOS

I need to put the MCU into low power mode.

I go the "power_mode_switch" example to work with my custom board.

I am attempting to convert the "power_mode_switch" example to work with FreeRTOS.

Around the calls to APP_PowerModeSwitch(), which calls SMC_PreEnterWaitModes() SMC_SetPowerModeWait(SMC), I used portENTER_CRITICAL() and portEXIT_CRITICAL().

portENTER_CRITICAL(); // stop the RTOS kernel tick timer

APP_PowerModeSwitch(SMC_GetPowerModeState(SMC), kAPP_PowerModeWait);

portEXIT_CRITICAL(); // resume the RTOS kernel tick timer

The FreeRTOS APIs did not keep the MCU in low power mode. I am guessing that an interrupt woke the MCU.

I would like to determine which interrupt woke the MCU. Can MCUXpresso catch the interrupt in the debugger?

The FreeRTOS docs do't cover this problem. Is there a "correct way" to do this in FreeRTOS?

Thanks,

Bruce

Re: How to wait in Low Power mode with FreeRTOS and Kinetis MKL16Z

bgraham — Thu, 07 Feb 2019 16:25:53 GMT

I think I have working solution.

I added a vApplicationIdleHook() that checks a global variable, and if set, it calls APP_PowerModeSwitch().

When an interrupt like the FreeRTOS system tick wakes MCU, the state of a user button is checked.

If pressed, the task that requested low power mode is sent an event, so that it wakes up.

Re: How to wait in Low Power mode with FreeRTOS and Kinetis MKL16Z

danielchen — Mon, 18 Feb 2019 15:41:32 GMT

Thanks for sharing this good idea.

Regards

Daniel