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The attached zip is a zephyr application that uses .92 uA in system_off sleep and idles at 2.65 uA on the Xiao nrf52840 (not sense). It demonstrates low power gpio interrupts and wake from system_off sleep.
power_test.zip (5.8 KB)
If using GPIO interrupts, the solution with Zephyr out of the box saves 9-10 uA at idle over Arduino. If you modify the Arduino interrupt code as described here Getting lower power consumption on Seeed XIAO nRF52840, the performance is about the same.
Since it looked like the flash was in dpd with my previous solution, I wasn’t sure what was consuming the extra power. I decided to sacrifice my Xiao for the quest. I took off the RF shielding and then planned to pull of parts one-by-one until I found where the extra current was going. I pulled of the flash first and current went to the low power target.
I didn’t have new ideas on how to change the Zephyr spi/qspi solutions, so I disabled the Zephyr spi/qspi functionality and implemented a simple module that follows from the Adafruit_FlashTransport_QSPI. Both Zephyr and Adafruit_FlashTransport use nrfx/nrf under the hood. The flash could probably be made functional by porting over the rest of the functionality.
Xiao nrf52840 with RF shielding removed
