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Capacitive Touch Sensing Solutions Slide 19

There are several registers that can be accessed which perform a certain number of functions. This module will now focus on some of the registers that perform critical functions. Refer to the device data sheet for a complete list of the registers and their functions. Two of the most important registers are the EVR (Environmental Variance Register) and the TVR (Touch Variance Register). Through the EVR, the user can specify the maximum change in capacitance that would be considered as a drift in the environmental conditions. The TVR specifies the minimum difference between the measured capacitance and the internal reference that would be considered as a valid touch. The two registers can be used to set the device to be able to detect different kind of touches: normal, light, heavy, with glove. By properly setting both registers, the touch sensor can have enough sensitivity to detect a touch with a glove, as long as it is not too thick such as surgical gloves, but not skiing or leather gloves. Thus, there can be enough sensitivity to sense a touch while wearing a glove, but not so high to detect noise, or to recognize as a touch something that is not. One specific condition to satisfy is that the EVR must always be smaller than the TVR.

PTM Published on: 2011-12-12