Driving LED1 signal on STPM32(electric meter ic) by STM32F1x

[sabaRamin]

Hi guys,

I connected STPM32 evaluation board (UART mode) to STM32F103 board.

I use of stpm32 firmware from st.com. and it work. I can measure and read rms voltage, rms current, active energy and.... . but when i set pulse/kwh LED on stpm32, I have below signal:

it is not a clear signal. it has a 50 hz on it too. why?

is it normal? or i must have only 0.721 Hz without 50Hz burst?

thank you