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Smart Bluetooth Forum Discussions

Anonymous
Not applicable

Hey,

I have noticed a high power peak lasts for 500 to 600 msec diretly after reset (or after wakeup from deep sleep entered by calling devlpm_enterLowPowerMode).. the peak level is about 5 to 6 mA. Tried with different apps and always the same. Last tried with rtc_sample default example: rtc_sample-BCM920737TAG_Q32 download


Tested on latest SDK 2.2.1.71

Attaching below a scope reading snapshot

Any explanation? if it is a well know bug, any workaround?

Thanks,

Ayman

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1 Solution
Anonymous
Not applicable

Hello Ayman,

This is expected behavior, since we need to calibrate the LPO.

For the first 500ms after boot, we disable sleep in order to calibrate the LPO and this is by design.

If you sleep while you calibrate the LPO, then there is no guarantee that you will wake up on time.

So the peak current in your screen capture is expected behavior.

Hope this helps,

Thanks

JT

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5 Replies
Anonymous
Not applicable

Hello Ayman,

Is the peak periodic?

JT

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Anonymous
Not applicable

each time you reset/powerup the module

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ShawnA_01
Employee
Employee
25 solutions authored 10 solutions authored 5 solutions authored

I believe this stems from the process of downloading the firmware from NVRAM into SRAM.   You could confirm this by programming a very small application, and measuring the time the peak is sustained.  Repeat the process with a much larger application... compare the two times.

One other thought... could this be a side-effect of the Crystal Warmup timer?   You could try changing that value as well.

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Anonymous
Not applicable

no.. confirmed that loading from nvram does not take all this time.

thanks for reply

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Anonymous
Not applicable

Hello Ayman,

This is expected behavior, since we need to calibrate the LPO.

For the first 500ms after boot, we disable sleep in order to calibrate the LPO and this is by design.

If you sleep while you calibrate the LPO, then there is no guarantee that you will wake up on time.

So the peak current in your screen capture is expected behavior.

Hope this helps,

Thanks

JT

0 Likes