Bluecoin power consumption - why and how to minimize?

[Part Robot]

Posted on March 30, 2018 at 14:16

Hi.

I'm noticing that when using the BVLINK or MEMS software with the device paired with an iPhone the BlueCoin is using about 40-45mA. This seems a high. I'm expecting 10-20mA maximum based on other similar products I've used in the past for similar use cases. Additionally, if the power battery levels reported in the iPhone app are accurate (which I doubt since at full charge it reports alternately 97% and 80% charged), then the device appears to shutdown when the LiPo is at 20-30% capacity. This power usage is the same even if the device isn't 'doing anything' - i.e. is merely paired with the phone.

Consequently I have the following questions:

1) Does this sound reasonable/correct?

2) Is it possible to shut down all other features to conserve power?

3) Is there an ultra-low power standby mode I can activate? How do I then wake the device?

4) What other power saving measures can I take?

5) Why does the battery level switch between 80% and 97% when fully charged?

Currently my only solution is to hard shut down the device and start it up again every time I wish to use the microphones.

Specifically my use case is to press a button to record some speech and the release the button to stop recording. The battery needs to last at least a week. My space requirements allow for a LiPo up to 500mAh.

I have read the docs available at STEVAL-BCNKT01V1 - BlueCoin Starter kit - STMicroelectronics but they are insufficient. Anything more related to actually programming the BlueCoin would be gratefully received as I'm very new to this particular type of device (I've only programmed Arduinos until now).

Many thanks,

PartRobot

#bvlink #battery-life #power #bluecoin

[Andrew Neil]

Posted on March 30, 2018 at 15:56

Any supporting documentation would be gratefully received

Here: 

http://www.st.com/en/evaluation-tools/steval-bcnkt01v1.html

  

[Part Robot]

Posted on March 30, 2018 at 15:58

Thanks but I mean supporting documentation related to the questions I have. I've read through all that and I don't see a reference to solutions for the above. I must add, however, that I don't necessarily understand all what I'm reading!

[Tesla DeLorean]

Posted on March 30, 2018 at 18:00

This might be better moved to the

https://community.st.com/community/mems-sensors-community/mems-sensors-forum

There needs to be better access to FAE and managers from the group responsible for the BlueCoin kit design.

The usual dynamic for that would be via your local ST sales and support contacts, although the expectations I think are shifting to more staff being available and responsive via 'social-media' or forum type venues. You're pushing these things into the hands of makers and engineers working out of garages/basements, not just large design groups at Apple/Nike etc with deep rosters of talent.

Kling.Brian

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[Part Robot]

Posted on March 30, 2018 at 18:08

Thanks Clive. Yes, that looks to be a better place to post this. I'll do that now.

I am finding it all bit opaque, as you point out. Fortunately the code is largely self-explanatory, but the hardware/HAL stuff is very sparsely documented and fragmented. Mostly I've figured things out by looking at the source code and ending up on random forums but it's not been easy

[Brian Kling]

Posted on April 03, 2018 at 09:20

I have moved this post over to MEMs and Sensors, so I'll delete the other one. I'll highlight this internally and see if we can't get some eyeballs on it!

[Part Robot]

Posted on April 25, 2018 at 19:46

Anyone have any thoughts on this? Issue still remains and Bluecoin is unusable for this project until we have some details about the low power mode.

[Davide G]

Posted on May 09, 2018 at 12:44

Hi,

I’ll try to reply in order.

1) Does this sound reasonable/correct?

Both firmware examples you mentioned (BVLINK and ALLMEMS) are not optimized for Low Power and the MPU is always running at full speed, no matter what the firmware is doing. This is why you always see 40-45mA.

2) Is it possible to shut down all other features to conserve power?

Yes it is, even though STM32F446 it’s not the best choice for very low power applications (STM32L family would be the best choice).

Here there is an application note about “Using STM32F4 MCU power modes with best dynamic efficiency�.

http://www.st.com/resource/en/application_note/dm00096220.pdf

Even if it isn’t specific for the STM32446 I think it could be a good starting point.

3) Is there an ultra-low power standby mode I can activate? How do I then wake the device?

4) What other power saving measures can I take?

At chapter 5.3.3 of STM32F446 Ref Manual

http://www.st.com/resource/en/reference_manual/dm00135183.pdf

you can find the details about the different power modes.

As an example, the device could be woken up using an interrupt coming from one of the sensors (like the accelerometer) or a button.

5) Why does the battery level switch between 80% and 97% when fully charged?

Not sure at this point. This should be investigated further.

[Part Robot]

Posted on May 11, 2018 at 10:38

That's perfect, thank you very much! Very clear.

So do I understand correctly that I don't need to consider the individual components and all I have to do is set the right interrupt and the whole device will sleep/wake/stop? If so, that's fantastic.

Also, thank you for pointing me to the manual - that's very useful