Low Power / Sleep on QT PY SAMD21?

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ichiban
 
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Low Power / Sleep on QT PY SAMD21?

Post by ichiban »

Hiya folks -
Finally getting back into some electronics after a long hiatus. Starting up with a little servo project that I'm hoping to run off of a QT PY SAMD21. I'd like to have the mechanism plugged in 24/7 in a low power state, wake using an interrupt, do its motor thing, then go back to sleep.
My question: is there an explicit "sleep" state into which I can put the SAMD21, or is the lower power draw just from the idle state?

Secondly and perhaps more strategically: what's the best way to create a 24/7 plugged-in device that is low power until needed? I assumed that my approach of "sleep + interrupt" was good, but I'm open to hearing something better!

Thanks in advance!

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mikeysklar
 
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Re: Low Power / Sleep on QT PY SAMD21?

Post by mikeysklar »

You can put the SAMD21 into a low power sleep with the Adafruit Sleepydog library.

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westfw
 
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Re: Low Power / Sleep on QT PY SAMD21?

Post by westfw »

I see that the SAMD21 can go pretty low but doesn't have the "deep sleep" of the ESP32-S2
The names of various power-down states are vendor-specific and somewhat random, and can mean random things.
The SAMD21's equivalent of "deep sleep" (ie lowest possible power) is called "standby", and has a bunch of options and different consumptions depending on which peripherals you leave clocked.

I'd generally expect the SAM to have better low-power behavior than the ESP chips (which are known for their wireless capabilities, not their low-power modes.) At 25C and 3.3V, the SAMD21 "standby" mode is spec'ed (Datasheet Table 41-7) at well under 100uA for all of the interesting operating modes, and under 5uA for some of them.

(Board-level power consumption may be a separate issue. Most Arduino-like boards are not really designed for low-power operation, and will have lossy voltage regulators, unnecessary LEDs, and etc.)

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ichiban
 
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Re: Low Power / Sleep on QT PY SAMD21?

Post by ichiban »

Thanks to both of you for your responses!

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dkepler
 
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Re: Low Power / Sleep on QT PY SAMD21?

Post by dkepler »

I'm also looking into putting the SAM21 into Low Power mode. Does anyone know which mode the watchdog library takes you (idle vs standby)? I'm trying to figure out the current consumption.

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mikeysklar
 
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Re: Low Power / Sleep on QT PY SAMD21?

Post by mikeysklar »

The sleepydog library uses standby mode, but you can enable idle mode before calling sleep.

Code: Select all

PM->SLEEP.bit.IDLE = n;
More on this issue which has a lot of good tips including one user who pulled their board (SAMD21 based) deep sleep draw down to 26uA.

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