Hello @koichirose
here is how I managed to get M5StickC Plus into deep sleep using MicroPython:
p37 = machine.Pin(37, mode = machine.Pin.IN, pull = machine.Pin.PULL_UP)
p37.irq(trigger = machine.Pin.WAKE_LOW, wake = machine.DEEPSLEEP)
machine.deepsleep(20000)
It wakes up from deep sleep either after 20 seconds or when button A is pressed.
Thanks
Felix