This illustration shows a simplified block schematic of STMicroelectronics’ capacitive sensing controllers. On the left, a host controller is required which communicates through I2C with the touch sensing controller. The copper sensing pads are shown on the right with the traces going into the front end of the detection engine. This is an example of a “Finite State Machine”. That means it has some intelligence built-in and registers they can access, but they are not micro-controllers. A couple of the advantages are that there are no worries about programming and memory or loading software. Communication is through I2C where the user can access the registers and transfer the data, or have available a “direct output” call on the GPIO mode, which means that some of the GPIOs can be activated directly without even going through the micro.