A developer has built an open-source multifunctional oscilloscope by repurposing an old Android phone, a Raspberry Pi Pico, and a custom-made PCB that integrates all necessary components. The project leverages the Pico’s 0–3.3V ADC, which requires a robust analog front-end to accurately capture and condition signals.
The custom PCB incorporates an analog input circuit designed to protect the Pico from overvoltage. Schottky diodes are used to clamp excessive voltage while a resistor network centers the input, allowing for the measurement of both positive and negative portions of an AC signal. This circuit supports multiple voltage ranges, including a ±330mV mode that employs a non-inverting op-amp configuration with a gain of 10, and a ±33V mode that uses a voltage divider to attenuate high signals.
Component choices are driven by the need for precision and safety. The op-amp provides necessary amplification without introducing significant offset, while an analog switching IC facilitates range selection by bypassing the feedback resistor when required. Additionally, a level converter module on the PCB enables the device to function as an 8-channel logic analyzer, further expanding its functionality.
The system runs on Scoppy firmware loaded onto the Raspberry Pi Pico, transforming the Android phone into a portable oscilloscope. This open-source project highlights a practical approach to combining custom electronics with readily available hardware, delivering a versatile tool for signal measurement and analysis.
