I require a periodic wakeup from shutdown-mode. For that I found two recipes: AN4759 (table 7) and RM0351 (section 34.3.7). Essentially they provide the same info. Unfortunately it did not work until I tripped over “When the periodic wakeup interrupt is enabled by setting the WUTIE bit in the RTC_CR2 register, it can exit the device from low-power modes.” (RM0351, section 34.3.6)
I added “
LL_RTC_EnableIT_WUT (RTC);” and it worked as expected.
I was puzzled because the NVIC is powered off in shutdown mode. So there are no interrupts.
Isn’t there something missing in the recipes? Is WUTIE really required?