This directory contains the drawings used on the Pi4J website to explain the architecture, code...
The drawings are made with draw.io
Check github.com/jgraph/drawio-desktop/releases for the latest version.
For example: installing 13.3.1 on Ubuntu:
wget https://github.com/jgraph/drawio-desktop/releases/download/v13.3.1/draw.io-amd64-13.3.1.deb
sudo dpkg -i draw.io-amd64-13.3.1.deb