I'm currently working with the Capacitive Liquid Level Sensor Kit . I think I have a good basic understanding of the basic principles behind the technology. On the sensor strips, I note an additional strip called TX0. In the 2 sensor strip sensor there is a single TX0 strip and on the 12 sensor strip there are two TX0 strips.
Looking at the TopDesign.cysch, I note a GPIO named Pin_TxGnd, which indicates this may act as GND. The pin is a Digital output with an initial setting of (Strong Drive)Low (0). On viewing with a scope the setting appears always to be zero. My initial thought is they act as a GND. CapSense essentially measures the Capacitance between the RX and TX strips. I guess, having the GND strips built into the sensor make the capacitance much more stable, rather than using RX strips alone.
When I think TX, the word transmit comes to mind, and since the GPIO is a digital output, there is the possibility of a setting other than GND. I'm not sure what can be achieved with other settings though.
