There's two probes on the osciloscope. We struggle a bit in the beginning because we try to mesure with one probe and the machine displays the result of the other one.
After this little "incident", we mesure the digital sensor, the swith: We have this waveform: With 5mV and 10ms. But it's the image of a floating pin. We forget to upload a code in there, so the pullup resistor wasn't on! We upload, the code and we finish to have