37.5 CVD Module Operation
The enhanced CVD uses the shared ADC SARCORE for its operations; see Analog-to-Digital Converter (ADC) from Related Links. The enhanced CVD controller controls the shared ADC SARCORE in a simplified mode that supports only the needs of CVD, performing the full sequence of an oversampled CVD touch scan.
The controller also controls pin functions needed for the CVD operations. Some of these pins provide RX functionality by having an analog. Some pins may have both RX and TX functions. The RX and TX pins connect to a matrix of button electrodes, a touch screen or touch pad electrode grid with horizontal and vertical structures. To determine a touch or an approach, measure the capacitance of these electrodes.
An AddCap module connects to the analog input net to augment the internal capacitance of the chip to match the base capacitance of the touch sensor. Measurements are triggered either by a CPU or a timer through EVSYS.