STM32F030C6 trying to use LSE

[kohei ishikawa]

Posted on April 02, 2018 at 11:26

Hi, I have a STM32F0C6 board and I'm trying to use RTC function with LSE.

It seems RTC is working correctly and I can check the waveform of LSE Clock from MCO pin.But when I check the waveform of OSC32_IN and OSC32_Out pins by using an OscilloScope,OSC32_IN: about 300mV flat lineOSC32_Out: about 1.3V waveform nearly LSE clock(32.768KHz).

Is this correct work of OSC32_IN and OSC32_Out?

please give me an information.

and let me apologize for my poor English.thank you.

[waclawek.jan]

Posted on April 02, 2018 at 15:24

The LSE oscillator is a very low power (thus high impedance) analog circuit, thus it is very easy to be influenced by the attached oscilloscope probe (which presents a significant load).

JW

[henry.dick]

Posted on April 02, 2018 at 15:37

sounds about right. probing the output pin is better, as its impedance is lower.

[T J]

Posted on April 02, 2018 at 16:27

you can use a 1Meg resistor in series with your probe,

then the oscillator should keep working whilst you are watching it.

but you will shift the frequency with the probe capacitance.

henry.****

‌ is correct, you should be probing the output pin.