A button is designed for the board, but is not functional and not mounted by default on this board. It is open for the user to use it freely.
The button connects on the PC5 pin of ATtiny817.
Figure 1. The Button
Figure 2. Schematic of the Button
Note: Resistor R106 (39Ω, 0402, ±1%) should
be mounted in series with button SW101 if the user must use SW101.