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Battery drain when EN pin is grounded
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Battery drain when EN pin is grounded

by weaVaer on Thu Jan 17, 2019 9:28 pm

We purchased quite a handful of Huzzah Feather ESP8266's during past year at different times for an ongoing R&D work;
most of them being F-series, the rest S-series.
and we are observing a strange behavior with some units.

We are connecting the GND pin to the EN pin on a breadboard that should effectively silence anything downstream of the regulator on board.
Otherwise nothing is connected to any other pins.
Some of the units are used and have sketches on them while some units are just-out-of-the-box things, never used.
But since we wont run the code, that seemed irrelevant but who knows ?

Then we introduce :) an adjustable power source (set to 3.7V in our case) directly to the LiPo battery connector on the unit which also displays the current demanded.
So we effectively tried to mimic a battery and see how much drain is on it. I hope this setup is appropriate.

We tried this setup with all those 20-ish units we have on hand.
The S-series units and one F-series unit shows 0 current drain from our power source but most of the F-series units display 6 mA in this state.
This would be a no-go to use the unit with an actual LiPo battery which would be depleted in a relatively short time even when power disabled.
After a bit of head scratching over schematics of the board, we decided to land here and seek information about it.

Any ideas are much appreciated.
Attachments
Huzzah.6ma.jpg
drains 6mA
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Huzzah.0ma.jpg
drains none
Huzzah.0ma.jpg (324.86 KiB) Viewed 347 times
Last edited by weaVaer on Mon Jan 21, 2019 7:19 am, edited 1 time in total.

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Re: Battery drain when EN pin is grounded

by gritnix on Fri Jan 18, 2019 5:20 pm

Ok, might really be way off here (take this with a big grain of salt), but that QFN chip (the square one right above the GND and ADC) is the Serial/USB converter. The power to that chip does not appear to have anything to do with the regulator, it's coming straight from VBUS which is tied to VBAT through a diode. The chip is a CP2104, but it appears that the numbering on that chip between the two pictures is a little different, so I'm wondering if maybe it's behaving a little differently between the two?

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Re: Battery drain when EN pin is grounded

by weaVaer on Sat Jan 19, 2019 6:42 pm

gritnix wrote:Ok, might really be way off here (take this with a big grain of salt), but that QFN chip (the square one right above the GND and ADC) is the Serial/USB converter. The power to that chip does not appear to have anything to do with the regulator, it's coming straight from VBUS which is tied to VBAT through a diode. The chip is a CP2104, but it appears that the numbering on that chip between the two pictures is a little different, so I'm wondering if maybe it's behaving a little differently between the two?


Yes, thank you
very keen eye and good observation

That really might be the culprit.
It would be interesting to hear from someone at Adafruit about this issue

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Re: Battery drain when EN pin is grounded

by weaVaer on Mon Jan 21, 2019 7:17 am

Following different posts about this issue where people went to such heights like cutting traces on board in order to bring the power consumption down to uA levels, I can see that this is a known issue where anything but the CP2104 powers down, causing an approx. value of 6 mA of power consumption from the battery even when the EN pin is grounded.

My question is;
why some different versions of Huzzah Feather ESP8266 boards obtained at different times from Adafruit acts differently with the same setup here ?

May I assume that this issue is only observed consistently with some batches of the product with series F designation on the ESP8266 module and a certain series of the CP2104 chip,
and the issue has been corrected for other batches or other versions of the product ?

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Re: Battery drain when EN pin is grounded

by adafruit_support_carter on Tue Jan 22, 2019 3:31 pm


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Re: Battery drain when EN pin is grounded

by weaVaer on Sun Feb 03, 2019 8:30 pm

Posting for a technical support request here in the forums as requested :

We have purchased like 40 Adafruit Huzzah Feather ESP8266's through 2018 from Adafruit and now we have recognized that 18 such 6mA-draining-the-battery-while-in-sleep kind of boards.
Although the devices function totally normal and successfull otherwise, this problem that we observed later on some certain batches of the boards prevents us from deploying because of the usecase of where these devices will be used (requires deepsleep and prolonged battery times).
Furthermore we are planning to buy at least 40 more such devices.

Our test setup methodology, results and observations as you can see on the previous posts here haven't seen a response from Adafruit for a long time.
What we observe is some certain batches of the product has this problem and the others do not and it is an obvious engineering issue as such; since later devices that carry the ESP-S series chip and a different batch of the USB-serial converter does not have this issue.

So we kindly request for a change of these 18 devices (out of ~40) with healthy ones
and a guarantee for return for another 40 devices if they will also have this draining battery while on sleep mode issue.
i.e. Adafruit Huzzah Feather ESP8266's.

kind regards

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Re: Battery drain when EN pin is grounded

by adafruit_support_carter on Mon Feb 04, 2019 1:29 pm

Then we introduce :) an adjustable power source (set to 3.7V in our case) directly to the LiPo battery connector on the unit which also displays the current demanded.
So we effectively tried to mimic a battery and see how much drain is on it. I hope this setup is appropriate.

The "weirdness" is entirely based on the measurements made from this test setup? Can you post a photo showing the setup.

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Re: Battery drain when EN pin is grounded

by weaVaer on Fri Feb 08, 2019 1:54 am

Here is the detailed setup and observations with pictures;

Please take note that;
among the nearly 40 products that have been obtained at various times and tested with exactly the same setups;
the undesired behaviour is only but certainly observed with a certain batch of Huzzah Feather ESP8266's,
namely the ones that carry a "ESP8266-F series" ESP chip AND has a CP2104 USB-serial chip with the designation "SIL 2104 F0IS0 1734+" on board.
The closeup pictures of these two different type of products are at the top of this thread.

:: SETUP

Setup is simply done by observing the current drawn when the "EN" pin on Huzzah is grounded

1) by connecting a variable DC supply to the battery connector on Huzzah

2) by connecting a multimeter in series with a LiPo battery to the battery connector on Huzzah

Huzzah.setup1.jpg
Huzzah.setup1.jpg (212.04 KiB) Viewed 215 times

Huzzah.setup2.jpg
Huzzah.setup2.jpg (189.25 KiB) Viewed 215 times
Last edited by weaVaer on Fri Feb 08, 2019 2:15 am, edited 1 time in total.

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Re: Battery drain when EN pin is grounded

by weaVaer on Fri Feb 08, 2019 1:56 am

:: HOW WE DID IT

Expectation is the display of 0mA current drawn when the EN pin is grounded
and the observation is all the Huzzahs we have except the ones as designated above behave towards this expectation.

Huzzah.setupEnv.jpg
Huzzah.setupEnv.jpg (300.31 KiB) Viewed 215 times
Last edited by weaVaer on Fri Feb 08, 2019 2:16 am, edited 1 time in total.

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Re: Battery drain when EN pin is grounded

by weaVaer on Fri Feb 08, 2019 2:01 am

:: HEALTHY BEHAVIOR

When The EN pin is not grounded, Huzzah draws avg. 74-76 mA
and when the EN pin is grounded, current drawn falls to 0mA (or to levels that can't be detected by our resolution)

Huzzah.healthy.enabled.jpg
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Huzzah.healthy.disabled.jpg
Huzzah.healthy.disabled.jpg (326.68 KiB) Viewed 213 times

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Re: Battery drain when EN pin is grounded

by weaVaer on Fri Feb 08, 2019 2:05 am

:: FAULTY BEHAVIOR

When The EN pin is not grounded, Huzzah draws avg. 74-76 mA
and when the EN pin is grounded, current drawn falls to 6mA
This observation is consistent with all the devices we have that has the said designations.

Huzzah.faulty.enabled.jpg
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Huzzah.faulty.disabled.jpg
Huzzah.faulty.disabled.jpg (316.59 KiB) Viewed 213 times

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Re: Battery drain when EN pin is grounded

by weaVaer on Fri Feb 08, 2019 2:09 am

:: UNITS THAT DISPLAY THIS FAULTY BEHAVIOR

Please take note that all the Huzzah ESP8266's we have that has the same batch numbers and chip ID's as in the picture below displays the same behavior consistently.
i.e. the ones that carry a "ESP8266-F series" ESP chip AND has a CP2104 USB-serial chip with the designation "SIL 2104 F0IS0 1734+" on board

We didn't observe any similar faulty behavior with Huzzah ESP8266's which has different ESP series designator and different CP2014 chip batch numbers (or serial id's).

Huzzah.faulty.jpg
Huzzah.faulty.jpg (278.87 KiB) Viewed 211 times
Last edited by weaVaer on Fri Feb 08, 2019 2:20 am, edited 2 times in total.

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Re: Battery drain when EN pin is grounded

by weaVaer on Fri Feb 08, 2019 2:10 am

We need to order 40 more Huzzah Feather ESP8266's which we are holding off for nearly two weeks now.
Any units that we have or we will have that displays this behavior is preventing our deployments because we can not prevent battery drain when the EN pin is grounded for storage or power-save type of needs.

We need to resolve this matter at the shortest time possible and needing your help in this issue.

Thank you

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Re: Battery drain when EN pin is grounded

by adafruit2 on Fri Feb 08, 2019 1:41 pm

hiya - we just saw this - so there was a change in the design which can be affecting you.
please look on the bottom of the PCB for a letter with a circle around it - probable (C) or (E)
you can ignore the silabs and ESP part # for now - let us know which revision code is working for you and which is not!

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Re: Battery drain when EN pin is grounded

by weaVaer on Sun Feb 10, 2019 9:26 am

Hiya back

After your comment we checked and observed that the boards with the mark (E) drains 6mA when EN pin is grounded
whereas boards marked with (C) does not exhibit this behavior, showing 0mA drain in our setup when EN pin is grounded.
In this case boards marked with (C) works for our implementation where no (or insignificant) battery drain is required when EN pin is grounded.

We are in need of 40 units with similar behavior with no drain and it seems that we already have 18 units marked with (E) which have been bought during last year and are unfortunately unsuitable regarding the requirements for which we are kindly seeking a replacement. In this case we intend to order 22 more units from the (C) kind immediately.

Thanks

unit_marks.jpg
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Please be positive and constructive with your questions and comments.