Need an Ultra Low MCU which has RTC with 32-bit sub-second wakeup counter

[DBhut.1]

Hello,

I am currently using STM32WLE5CC MCU, which has a great feature of RTC with 32-bit sub-second wakeup counter, But I need a low cost MCU for my other non lorawan project, which also need this "RTC with 32-bit sub-second wakeup counter" feature.

Please suggest MCU in Ultra low Power with RTC with 32-bit sub-second wakeup counter, and if this sub-second counter underflows, then it generates interrupt.

Thank You

[waclawek.jan]

AN4759 has a nice table with RTC features across STM32 families.

However, what you are looking for is probably the binary mode, which is supported only by RTC v3 and also that only in 'WL and 'U5 families.

JW

[DBhut.1]

Thanks

[Piranha]

Most likely he means RTC_WUTR register, which is present on most STM32 series. And that wake-up down-counter is 16-bit wide.

[DBhut.1]

RTC_WUTR  doesn't have underflow interrupt.

[Piranha]

Yeah, why would anyone read the reference manual...

"when it reaches 0, the WUTF flag is set in the RTC_SR register, and the wakeup counter is automatically reloaded with its reload value (RTC_WUTR register value)"

"When the periodic wakeup interrupt is enabled by setting the WUTIE bit in the RTC_CR register"