Touch sensor, called CapSense in PSoC, can be implemented in two ways: CSD or CSX. It uses an ADC to measure the change in capacitance, and hence, the CapSense block can directly be used.
CSD implementation requires a copper pad that acts as a button, and this measures the change in capacitance to determine the presence or absence of a touch.
CSX uses a Tx and an Rx electrode to measure the mutual capacitance formed between them to detect a touch.
You can also check the code examples provided with PSoC creator or modus toolbox for getting started with CapSense coding.
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