Not exactly schematics, but [Duckman] has some Arduino pinout diagrams he made using ASCII-art. These could be useful when pasted into source code as comments, documenting the pinouts for your ...

Draw.iO Diagrams is a cross-platform diagramming application you can use to create flowcharts, workflows, org charts, Venn diagrams, wireframes, network diagrams, and just about any other chart or ...