“The circuit board presented here enables the exact mains frequency measurement of the power supply system (50 Hz and 60Hz). It is universally constructed and can be operated with a RaspberryPi 3/4 as well as with a USB-TTL converter.
The output of the measurement data is done via the serial interface of the used ATMega328. The µC software is programmed with the Arduino IDE. The program can be easily extended or adapted.
The reproduction is very simple.”