Are there any fundamental differences between CapSense in PSoC 3/5 vs 4/6 ?
PSoC 3/5 uses an older generation of CapSense in it. The CapSense block present in the latest PSoC devices such as PSoC 4 and 6 uses the latest generation of CapSense that has better SNR, high parasitic capacitance support and higher accuracy.,
We highly recommend you to use latest generation of CapSense devices (PSoC 4S/ PSoC 6) devices for newer designs.
Also, the basic working of CapSense in both these devices is the same, except that PSoC 3/5 uses UDB resources for CapSense whereas PSoC 4/6 has dedicated hardware block for CapSense.