Gemma M0 sleepydog: sleep current 16mA seems high

[ShelM]

Hi...

I'm using a Gemma M0 with 16-RGB-neopixel ring as an earring, and want to maximize battery life (== minimize weight). I'm running the neopixels very dim, and calculate/measure they are using < 3mA.

I've looked high and low for advice before posing my question, but have struck out. 8^(.

I turn off dotstar and the builtin led, and I'm using SleepyDog. I monitor current draw while I'm attached via USB (though I'm not doing serial communication).

In normal operation, current draw is ~28mA. During sleep(), with all neopixels off, current draw is ~16mA. This sleep current seems BANNED high to me. Any thoughts?

Bests,
...Shel

[ShelM]

Follow up note: I now know what the problem was..."fog in the cockpit" (as we used to say at Northstar Avionics). I failed to note that the feather board was *not* the only current user on the 5 volt line. The 16 neopixels were sucking down almost the full 16 mA that I noted when the MCU was asleep. The WS2812B driver chips in each neopixel have a quiescent current draw of ~1 mA each.

Tests with the 5 v buss disconnected from the neopixels show ~12 mA draw from the feather when not sleeping, and ~zilch when asleep - all is good!

Actually, only sort-of-good. 8^) I wish there were a way of getting the simplicity of WS2812B drivers without the current drain. I know, I could use a MOSFET to de-power the neopixels periodically, but that would restrict me to pulsed lighting.

Any thoughts on mitigating the problem would be appreciated, but at least I'm happy to know that SleepyDog really does a real thing.

Was thinking about dotstars, but the APA102 data sheet doesn't mention quiescent current - while an online site states that 0.7 - 1.0 mA is typical for APA102. Plus more challenging wiring in a wearable. Bummer!

...Shel