I hope it's OK to cross-post this question: https://arduino.stackexchange.com/questions/88618/achieving-low-power-with-arduino-zero-clone-seeeduino-cortex-m0. I'm getting a bit desperate.
I have Seeeduino Cortex-M0+, which is a functional clone of Arduino Zero, both using Atmel SAMD21 MCU. It is powered from 12V battery directly to 12V PWRIN jack. Current draw for LED blink test is 18mA. I tried two low power libraries:
In both cases, the current draw dropped only to 12.7mA, which is still huge. I checked the datasheet of MP1496DJ-LF-2 step-down, switch-mode converter used by this board and its quiescent current is below 1mA, so it doesn't look like the source of high current consumption. I've read posts about Arduino Zero running on 5mA from 12V input in low power. What else can I do in order to get the current closer to 5mA?