Card.attn restarting my host and notecard when running under battery

@ssozonoff yeah, the constraint here is with the AF power supply, not the PS on an individual MCU. Even with the AL, you’re going to want to add a bi-directional level-shifter like this one from Adafruit. To use this particular level-shifter, you can hook side A to the Notecard/Notecarrier with VCCA powered by VIO, and the B side to a Feather powered by the Feather’s 3V3 output. That will allow you to shut down the I2C bus without drain when the Feather’s power is killed by the enable pin.

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Hi,

Thanks and I guess this is pretty much the same answer for the following experiment.

I powered the Feather M0 + Notecarrier AF from the Feather’s JST battery connector (I realise this is not recommended per your documentation). In this case I am able to shutdown the Feather’s regulator by pulling the EN pin low. Non the less I still consume around 10mA.

Testing the feather on its own and connecting the EN pin to GND I am able to reduce the power consumption to around 70uA.

My understanding is that the I2C bus should only consumer current when its sending data and otherwise its in a high state.

Kind thanks,
Serge

Following on from the previous I am now swapping over to the Swan board which I received today. First thing of interest is it seems that if you power the Swan from its JST connecter it will not power the Notecarrier at all contrary to the Feather M0.

See below. The 3V3 supply on the AF powers both the Notecard and Feather, the the F_EN pin goes to the Feather EN and EN on this 3V3 supply. You can test this yourself by removing the Feather from the AF and pulling EN to ground, which will disable the Notecard.

So I am assuming I can cut the EN trace on the top side of the AF PCB in order to isolate it from the AF’s PS and hence only affect the Feather board when I pull it low with the ATTN pin. This would avoid everything restarting. I realise it does not address your comment about isolating the I2C lines.

Thanks,
Serge

@ssozonoff If you will attach a picture (PDF, diagram, hand drawn picture, etc…) of you proposed modification, I will try cutting the trace on mine, so you don’t need to test your theory on your own hardware.

Cheers,
Zak

Hi Zak,

Here is a picture of what I am proposing.

Thanks,
Serge

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@ssozonoff It works!

Cutting the trace you identified above, allows the Notecard to successfully power down the host MCU, without disabling itself. Furthermore, I was able to witness the power draw from a LiPo (connected at the BAT JST terminal) averaging slightly less than 50uA.

As noted before, even with this modification, the Notecarrier-AF cannot achieve the same optimal performance as the Notecarrier-AL, due to its inability to isolate the I2C lines. Using the same test sketch with a Notecarrier-AL averaged slightly less than 12uA.

Great detective work!
Zak

Hi Zak,

Thanks for confirming this, its great information you have provided here.
For me it boils down to a tradeoff between a fairly compact prototype sleeping with a bit more current consumption versus a solution built up of several PCB’s and hanging wires going between them but more efficient in sleep mode. I have yet to decide which one I will go with.

Kind thanks,
Serge

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Can you just confirm what you were using as a Host ? The test you performed on the AL was with the I2C isolation circuit ?

Thanks,
Serge

Me again,

I am unable to obtain 50uA with the AF carrier and a Swan as the host using ATTN → EN pin too shut the swans regulator down. This is with the modified AF board per discussion above.

Any tips.

Thanks,
Serge

Hi Serge,

I was using the Swan as a host, and I did not isolate the I2C circuit. The Notecarrier-AL provided the power for both components via the BAT JST plug.

I used jumper wires to connect the following pins on Notecarrier-AL → Swan.

  • <BATBAT
  • GNDGND
  • SCLSCL
  • SDASDA
  • ATTNEN

Also, you will need to wait for all the initializations to complete, before it drops into idle and achieves low power.

Best,
Zak

NOTE: I used a Current Ranger to determine the amperage.

Hi Again,

When I tested the Notecarrier-AF…

I was using the Swan as a host, and I did not isolate the I2C circuit. The Notecarrier-AF provided the power for both components via the BAT JST plug.

I plugged the Swan into the Feather socket, and used a jumper wire to connect ATTNEN.

Thoughts:

  • Do you have any way to confirm your modification worked as expected?
  • Did you wait for a few minutes (2-5) to make sure the Notecard had done all initializations and handshaking it requires on cold boot?
  • Is your Notecard connected with Notehub?
  • Are you connecting using a periodic connection?

If the modification would not work as expected then everything would simply reboot and nothing in the host would never be idle.

I have waited yes and it settles down at around 240uA which is way higher then what you are seeing, I am using a Joulescope. As mentioned I have connection set to off so notecard should be idle.

I will keep testing and see if I can come up with better results. I will also get around to test the AL but wanted to first see what the best results are I can get from the AF. I would at the very least like to see the same you are seeing.

Thanks,
Serge

I can also confirm that if I simply pull the Swan from the Notecarrier AF I am measuring an idle current of around 40uA.

And I can also confirm that the Swan on its own with a wire pulled from EN to GND consumes 2.5uA…

So now to figure out where all the current is going when the two are combined!

It could be the I2C lines but does not explain the difference I am seeing against that of zfields !

And for comparison using an Adafruit Feather M0 as a host I am seeing about 9.5mA of current when EN is pulled low so the Swan is better in this respect out of the box. Current during activity for the Swan is higher but I assume there is some trickery I can do to bring that down like lower the clock speed.

Just to confirm:

  • Do you have anything else wired up, other than a jumper between ATTN and EN?
  • Are you using the same example sketch, SleepySensor?

~Zak

Hi Zak,

Nothing else wired up however using my own sketch. I did review the SleepySensor sketch and saw nothing special but I can of course test it as well.

Thanks

So just tested with your SleepySensor sketch and getting same 245uA current.

That looks nearly identical to my setup.

Is the Notecard connecting to Notehub successfully?