We are using STM32WB55RGV6 in our design. Using both HSE and LSE. We use LSE for RTC setup. There is a time lag of apr.2 Secs in RTC per day( 24hrs apr). Please suggest. LSE crystal is NX2012SA-32.768KHZ-EXS00A.

[Martin_S]

A typical watch crystal like this one has an error of +/-20ppm, which is about 2 seconds per day. So your board performs very well at about -2ppm within the specs. Furthermore RTC supports digital calibration by adding and/or subtracting individual RTCCLK pulses. See Reference manual chapter 29.4.1.1 RTC smooth digital calibration.

If you need higher precision you have to change crystal to other oscillator types like OCXO, but at the price of much higher cots and power.

[Bouraoui Chemli]

Hi @bredd.1​ 

The used LSE crystal is compatible with STM32WB. However, for more information about oscillator compatibility with STM32, I suggest you to check AN2867 for LSE crystal and AN5042 for HSE crystal.