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Here is a PDF that describes a lot of the issues/questions that you might have while working with the PSoC parts and their CapSense API:
While I have not used the PSoC parts for cap sensing, there are a lot of resources out there to do this kind of interface. One of the most challenging cap sense projects that I have worked on was on a medical device, that used three sensors, closely spaced around the tip of our device. The goal was to only allow the device to operate if all three of the contact sensors reported making skin contact. The cap sensing was performed with a very simple GPIO type approach using a simple PIC part ( see IoT Haunted Doorstep - Part 2 - Breadboard Basics for a very good explanation of the process). Tuning and performance for this application was critical as our product was using a very high power laser and FDA requirements made in necessary for us to provide a verifiable and proven technique that would not fire the laser, or stop the laser, if any of the three sensors reported a break in contact. The performance of the sensor was dependent on the series resistor values that we used, too high and sensing was slow, or too low and the contacts would not sense contacts at all.
Good luck on finding a solution.