This project shows how a Raspberry Pi Pico board can be used as a low frequency oscilloscope. The RP2040 sampling speed is limited to 500ks/s. The board communicates via an USB serial interface with an user program written in HTML / Javascript that uses the Web Serial API for communication. At the moment of writing this API is only supported by Chrome, Edge and Opera.
The program for the Pico is written in C and requires the Pico SDK for compiling. An .uf2 file is available for programming the board without use of the SDK.
The user interface is simple: adjust the position of the vertical green line to change the default 50% trigger position and adjust the horizontal green line to set the trigger level. Other settings are done with checkboxes and sliders.
One of the PWM's on the Pico is programmed as pulse generator with frequency and duty cycle setting in the user interface.
The connections on the Pico board are:
GP26 : analog input for channel 1, input range 0-3.3 V
GP27 : analog input for channel 2, input range 0-3.3 V
GP22 : digital output PWM pulse generator