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LLWU using LPTMR0 on K22F not waking

Question asked by Alexander Farley on Jul 24, 2017
Latest reply on Jul 25, 2017 by Alexander Farley

I'm trying to use the LLWU triggered by LPTMR0 on a K22F to wake from sleep. I've based my code so far on this guide:

Starting Point for Kinetis Low Power LLS Mode | MCU on Eclipse 



My goal is to put the system into low-power mode, then periodically wake using a low-power timer *without* resetting system state. So, I don't want to re-enter at main; I just want the MCU to pause while it's sleeping until the timer goes off.


The timer interrupt is being triggered but Cpu_OnLLSWakeUpINT is never executed after the processor goes back to sleep. Here's some background on my configuration:


-LPTMR0 configured to use LPO_1kHzSrc

-Very low power mode, Low leakage stop mode, Very low leakage stop mode all enabled under Cpu component

-LPTMR0 checked under "LLWU Settings" under Cpu component

-interrupt request enabled under LLWU Settings, Interrupts

-interrupt priority set to Highest

-Return to wait after ISR is disabled for both WAIT and SLEEP

My best guess is that this is happening because the TimerUnit_LDD interrupt handler is clearing the LPTMR0 before Cpu_OnLLSWakeUpINT gets executed. In fact, I can see this line in the PE-generated code for the timer unit:


/* {Default RTOS Adapter} ISR parameter is passed through the global variable */
WakeupTimer_TDeviceDataPtr DeviceDataPrv = INT_LPTMR0__DEFAULT_RTOS_ISRPARAM;

LPTMR_PDD_ClearInterruptFlag(LPTMR0_BASE_PTR); /* Clear interrupt flag */
WakeupTimer_OnCounterRestart(DeviceDataPrv->UserDataPtr); /* Invoke OnCounterRestart event */


What I don't understand: in the blog post above, the PE-generated code seems to be working fine according to the author.


Something I don't quite understand: what's the distinction between the TimerInterrupt event vs. the Cpu_OnLLSWakeUpINT event? If I have configured LPTMR0 as a LLWU source, I would expect that both the TimerInterrupt event and the LLSWakeUp event to occur. 





1) Could this be caused by the fact that LPTMR is enabled as an LLWU source but LPTMR_CMR is not? 

2) Somehow, *other* interrupts (not the LPTMR) are able to wake the processor and start it running again. I've set a breakpoint in Cpu_OnLLSWakeUpINT and it doesn't appear to be executed, so I'm not sure how or if the processor is waking. For example, I can transmit a UART character into my MCU (which triggers a different interrupt) and then everything starts running again. These other interrupts are not LLWU sources.