High-speed equivalent-time sampling virtual instrument based on microcontroller ADC

The paper describes the utilization of high-speed Equivalent-Time Sampling (ETS) in Software-Defined Instruments used for virtual instrumentation - typically oscilloscopes. With the increasing performance and expansion of peripherals of microcontrollers (MCU), it is possible to realize measuring instruments only with MCU itself. A solution to MCUs' Analog-to-Digital Converter (ADC) maximal sampling frequency limitations in digitizing quick transient responses is presented. The principle of ETS with all derived equations is discussed and explained, as well as the ADC input model and real properties of software-defined oscilloscope from an ETS point of view. All the ideas are practically verified on different MCUs (Raspberry PI PICO, STM32, Arduino). The use of ETS for circuit behavior analysis where an MCU with internal peripherals (generator with pulse-width modulation and ADC) is used for a test signal generation and data digitization may increase the equivalent sampling rate of the internal ADC up to tens of MSa/s.