How to go to sleep (lightsleep or deepsleep) on SAMD21 and wake up on an input pin?

[avillacis]

I am currently dipping my feet into MicroPython, specifically the SAMD port. As part of this, I am trying to port an Arduino project I wrote some time ago. One feature of this Arduino project for the SAMD21 (Arduino Zero compatible) is the use of the Arduino Low Power library to enter a sleep state, and to wake up from said sleep state when a particular pin is asserted (an IRQ pin from an accelerometer). I have browsed the MicroPython documentation and I see the methods to enter light sleep and deep sleep, but I do not see a way to make a machine.Pin wake up the board on an incoming signal.

The MicroPython documentation references a wake parameter of the Pin.irq() method, to be used with the constants machine.IDLE, machine.SLEEP or machine.DEEPSLEEP. However, these constants are not available in the machine module for the SAMD21. Also, from a cursory examination of the source code, the SAMD port does not appear to implement the wake parameter either.

Is wake-on-pin available in the first place in the SAMD21 port?

The firmware file I downloaded is: SAMD_GENERIC_D21X18-20260406-v1.28.0.

[robert-hh]

The lightsleep and deepsleep methods do not use the Arduino Low Power library to enter a sleep state. Instead, the board is just configured to the lowest suitable clock frequency, which is 200kHz. The firmware stays active, but at low pace and low power consumption.
If at that time a Pin IRQ is noticed, the board MCU is reconfigured to full speed again.
So you can use any pin as wake pin. You only have to configure a Pin.IRQ for that Pin before calling e.g. lightsleep. The only difference between these two is, that with deepsleep a reset is performed when the sleep terminates.
The current at lightsleep/deepsleep is about 500µA for the SAMD21, measured with a SEEED XIAO board with removed power LED. But that will vary with each board configuration. You can get a similar behavior by just configuring the board to a lower clock frequency using machine.freq(). The lowest accepted value is 1 MHz. USB works down to 8 MHz clock frequency.