RTC alarm with sleep mode does not work, WiPy never wakes

[toy]

Hi, the issue is not completely new. In a previous firmware update it is listed as a known issue ("RTC periodic alarm with sleep mode is unstable, sometimes the WiPy never wakes"). However, the same problem occurs also in single mode (repeat=False). My wipy never wakes up from sleep mode when using the RTC alarm (I am using a wipy 1.0 with latest firmware and pycom extension board vs 1.0). Quite disappointing.

That's the code I used to implement the RTC alarm (without success)

import machine
from machine import RTC
import os
import time

rtc = RTC()
rtc.alarm(time=500, repeat=False)
rtc_irq = rtc.irq(trigger=RTC.ALARM0, handler=None, wake=machine.SLEEP)
machine.sleep()

I can get the wipy to wake up (using identical code) by connecting to an ftp client or when I use REPL.