use STM32Club, configure STM32WB55 but fail to select LSE as RTC input.

[MLy.1]

Hi,

I followed this setting here

https://community.st.com/s/article/how-to-configure-the-rtc-to-wake-up-the-stm32-periodically-from-low-power-modes

But still not able to select LSE as RTC source.

What steps I missed? Please help.

Thanks!

[Peter BENSCH]

You seem to have overlooked point 4.6 of the tutorial:

6. Activate the clock source and enable the Internal WakeUp

• First click on “Activate Clock Source�? to enable the clock to the RTCperipheral.
• [...]

You can find it under the tab Pinout & Configuration in the peripheral RTC, either via

• Categories > Timers > RTC

or

• A->Z > RTC

Hope that helps?

Good luck

/Peter

[MLy.1]

Hi Peter,

Thanks for the reply.

I did Activate Clock Source and select Internal Wake Up, see photo. but in the Clock Configuration, LSE is bold but the dot is in LSI line.

Do we need to special parameter setting? I also set WakeUp counter as 0x500B.

Why the instruction highline Tamper1? Do we need to select that?

Any idea?

thanks!

[Peter BENSCH]

Correct, if you only activate the RTC, after switching to the tab Clock Configuration, the selection item appears in light blue in the RTC Source Mux.

Are you sure that you clicked on the empty circle at LSE and thus selected LSE?

To find out how to use the RTC, it is strongly recommended to read section 29 (RTC) and possibly section 8 (RCC) in RM0434.

With a 32kHz crystal, no change of the default parameters (Async Prediv=127, Sync Prediv = 255) should be necessary.

If you activate WakeUp, you can trigger an interrupt after an appropriate time, which is needed for the number of WakeUp Counter Clocks with an appropriate WakeUp Clock. The WakeUp Clock is RTCCLK/16 by default, but can be set to other divisors or clocks (1Hz, etc), as shown in detail in RM0434.

The function of the tamper pins is also explained in section 29 (RTC) of RM0434. If you don't need any protection against intrusion into your system, you can leave this deactivated for the time being.

Regards

/Peter

[MLy.1]

No, click on the empty circle at the LSE does not work. it does not appears light blue.

Please take a try at your side to see if you have the similar problem. Thanks!

[Peter BENSCH]

I had already checked this in my first post, but have just double-checked it again:

As soon as you:

1. set the LSE in the RCC block to Crystal/Ceramic Resonator and
2. activate the clock source in the RTC block

LSE can immediately be selected as the input frequency for RTC in tab Clock Configuration.

If you also activate RCC > HSE, you can also select HSE_RTC as clock source in tab Clock Configuration.

Which version of CubeMX or CubeIDE are you using?

Regards

/Peter