An amazing resource to get started with custom EC board design is Tom Smalley guide on Github. Despite the fact that the last update dates back to 2017 it still holds up, both in terms of information and relevance.

In a nutshell, continuing from the patent description, we need a sensing system that can detect the variation in capacitance of each switch in the matrix. The way we do it is by utilizing a circuit like the following:

We can identify 3 sections:

• Matrix and analog multiplexing
• RC decay
• Signal boost and protection

Now that we have covered the basics of how the keypresses are detected we can move on with the actual PCB reverse and design work: PCB Design