Thanks boarchuz, your suggested change solved my problem

How did you find out that the ULP code should use RTC_IO_TOUCH_PAD3_REG instead of RTC_CNTL_HOLD_FORCE_REG to hold/unhold GPIO15?

Thanks for your fast answers and sorry for my delay ... we have public holidays this week here in Austria. Attached you can find my test implementation which initializes the used pins once at power up, starts the RTC timer to wake up the ULP every second and then put the chip into deep sleep. The UL...

Hi I'm not sure if misunderstand the technical reference manual or if my code is incomplete. The manual says ... " Users can use the hold function for the pads to retain the pad state through a core reset and system reset triggered by watchdog time-out or Deep-sleep events. " ... and I would expect ...