OSCAR

To use your Arduino UNO as an oscilloscope, you just need two wires and OSCAR. The Arduino captures the signal while the PC provides a full graphical interface for displaying and analysing it. With no additional hardware, OSCAR can measure signals from 0 to 5 V at sampling rates of up to about 150 kS/s. It includes automatic, normal and single trigger modes, voltage and frequency measurements, spectral analysis, configurable windows, and CSV export for further processing. OSCAR is also an educational project: its source code is freely available, so you can study, modify and improve it while learning about ADCs, sampling, aliasing, triggering and digital signal processing. The complete design and development process is explained in the book: Arduino, Tcl/Tk Oscilloscope.

Source code at https://github.com/hykrion/arduino-tcl-tk/tree/main/osciloscopio