PowerManagement_ForceSystemPowerDown don't works propertly

Question

Hi everyone.

I have problems with the Azure Sphere Powerdown cycle; even using the base example* that Microsoft Azure Sphere provides in their git samples :  https://github.com/Azure/azure-sphere-samples/tree/main/Samples/Powerdown

I seems to does not matter the time that I passes as a parameter to the function

ForceSystemPowerDown(unsigned int maximum_residency_in_seconds);

The time durring which the app is in low voltage (Powerdown) is only 30 seconds.

I have tested it with 2 boards : the Seeed MT3620 Mini Dev Board and the QIIO q200.

Do you have any idea how to fix this bug?

To reproduce the bug, just use the same git example (previous link) and try different times on the line.

// time in seconds that device will be in powerdown mode (sleep);
static const unsigned int powerdownResidencyTime = 600;

Thank you very much, your help will be greatly appreciated.

Dan

*the only modification are those necessary for used with my developments boards like hardware définitions, etc.

Answer 1

Hi @dhc I am posting the findings from the GitHub issue here for the benefit of other community members.

This could be an issue with the wiring of the boards/modules being used here - using power management requires the PMU_EN pin to be tied to ground (which must be done manually on RDB revisions 1.0 through 1.4, but is pulled down by default on revision 1.6 and up). We don't believe this pin is brought out on the AI-Link module used by the Seeed mini dev board, so it would depend on how the module itself is configured;

You can check to see if this is the cause - with the dev board attached over USB, attach a serial console to the recovery UART (which should the highest-numbered UART on the FTDI interface) at 115200 8N1, and observe what happens when the device attempts to enter power-down. If there's a line which says [PLUTON] !! ERROR: ERROR: Clearing RTC PMU_EN register failed to power down device, it is likely this is the cause (i.e., PMU_EN is not pulled low).

There are further notes on power down mode and hardware considerations

Please let us know if you have any additional findings or observations that would help other community members facing a similar issue. I highly appreciate your contribution to the community.

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