Any tips for using RTC Output pins while under the battery power (VBAT) domain?

[EGouz.1]

Using an F411, I'm having trouble getting the RTC_AF1 (PC13) pin to trigger while powered only by the VBAT pin. The pin seems to drive correctly when VDD is active (tried both Wakeup and Alarm A), but removing VDD does not have the same effect. Is there something special I'm missing?

[waclawek.jan · Accepted solution]

Read out and check/post RTC registers content.

JW

[EGouz.1]

Thanks for the response, in grabbing the registers to post here I found the LSI had been configured as the RTC source instead of the LSE.

[waclawek.jan]

Thanks for coming back with the solution.

JW