Notecarrier-F: "ultra-low-power" is still 2.5mA

Hardware
1

I am trying to setup an ulp-system with the Notecarrier-F. I am setting the notecard into “minimum”-mode, otherwise I am using
card.attn(mycard,mode="sleep",seconds=sleep_time)
to trigger low-power mode as described in the guides. The dip-switch on the back of the F-Carrier is set to N_ATTN.

The setup basically works, i.e. the notecard cuts power and the Feather stops working. After the sleep-time the Feather resets and starts up again.

Now when I measure current consumption, I am stuck at about 2.5mA@3.6V (using V+ or VBAT). When I provide power via the Notecard-USB, the figures are 7-15mA@5V (the value oscillates in this case, while being stable for V+/VBAT).

Is this to be expected or am I missing something? I would not call 2.5mA “ultra-low-power”…

2

Hi @datalogger,

If you’re using a 2mA draw, it sounds like AUX may be enabled. You can try disabling it with:

{"req":"card.aux","mode":"off"}

Your target should be 8-12uA @ 5V depending on the specific Notecard you are using (with several additional uA depending on the Notecarrier in use).

Rob

3

Hi Rob,

thanks for the fast response. Sadly, turning AUX off had no effect.

4

Hi @datalogger,

When I’m testing a Notecard to get it into its lowest power consumption mode, the below requests are all of the steps I take. This is the nuclear option of course :slight_smile:, but chances are one of these commands will undo something previously set that continues to draw current.

{"req":"card.restore","delete":true}
{"req":"hub.set","mode":"off"}
{"req":"card.motion.mode","stop":true}
{"req":"card.location.mode","mode":"off"}
{"req":"card.attn","off":true}
{"req":"card.aux","mode":"off"}
{"req":"card.sleep","on":true}
{"req":"card.io","mode":"+busy"}
5

Hi Rob,

thanks, I will give it a try and report back. Some of the settings are not relevant for my card (e.g. the card.sleep), but I will try the other ones. And the card.restore will be the last resort, since it would need reinitializing everything.

6

Hi Rob,

this did not change anything. But I skipped the card.restore for now, because I noticed that I am still on firmware 5.3.1. I did not read anything in the release notes that there were updates to the ULP functionality, but maybe I should upgrade to the current firmware anyhow before further configuration/testing.

What do you think? Thanks!

7

Ah yes, I would try upgrading to 7.5.2 as there were some related changes made earlier this year. If that’s not it, we can dig deeper!

Rob

1 Like
8

Hi Rob,

with 7.5.2 I am down to 335µA@3.6V :slight_smile: This is still not in the anticipated range, but I think it is good enough for now. If you have any other suggestion what to try, please let me know.

Thanks for your support!

9

There is a lot of capacitance on Notecarrier F which is likely why you’re seeing those numbers. In my experience, the best low-power results will be seen using Notecarrier A.

Rob