MBED LowPowerTimeout and MDot Deep Sleep

[Ajay K]

Consider this scenario, let’s say the mDot has a sleep interval of 1 minute which wakes up based on RTC Timer and the WatchDog timer resets the MCU at every 32 seconds, when not kicked. Also I attach a method to a LowPowerTimeout MBED driver to execute every 20 seconds to kick the watch dog timer, so as to prevent the MCU from resetting.

I have the following question regarding LowPowerTimeout driver available in MBED and not sure I understand the concept of LowPowerTimeout completely and hence the questions.

1) Does the LowPowerTimeout attached method gets called even when the mDot is in deep sleep?

2) If the method is called during mDot sleep and it attempts to kick the watchdog timer, will it break the mDot out of sleep?

Thanks,
Ajay

[Ajay K]

Amy thoughts multitech team?

[Jason Reiss]

https://os.mbed.com/docs/mbed-os/v6.7/apis/lowpowertimeout.html

[Jason Reiss]

Code is not running while the device is in sleep mode. When code is running the device is awake.

I think the mDot does not enter the deepsleep mode regardless of requested sleep. This should show in the debug logs. Debug version of at firmware could be used to test.
https://github.com/MultiTechSystems/Dot-AT-Firmware

The mDot lib does not allow deepsleep as the hardware cannot reach the lowest expected current.

Deep sleep on mDot does not retain ram and lowpowertimeout would not work.

Deepsleep options to wake up would by RTC alarm or interrupt.

[Leon Lindenfelser]

The mdot library sleep and deepsleep place the processor in stop mode. If you want to wake up to reset the watchdog every 20s, I recommend configuring the sleep function to wake every 20s to do that. Don’t add another LowPowerTimeout. I recently worked with someone who was testing out the possibility of using more than one timeout to wake and it can create problems in rare instances.

[Ajay K]

Thanks Jason for taking the time to respond. I meant in the current supported sleep mode in mDot, which is not deep sleep mode would the LowPowerTimeout attached method get invoked even when the mDot has entered the supported sleep mode. If so I am guessing it would break the mDot out of its current supported sleep mode?

Thanks,
Ajay

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