Patent ID: 8542215
Filing Date: 2013-09-24
Classification: G06F,H03K

Abstract:
1. A method for determining multiple touch events in a multi-touch sensor system having a capacitance measurement unit comprising a relaxation oscillator circuit, a pulse drive unit, and a touch sensor having a plurality of nodes and a plurality of electrodes comprising at least two sets of electrodes, the method comprising: connecting a first electrode in a first set of electrodes to the relaxation oscillator circuit within the capacitance measurement unit; driving, with the pulse drive unit, a voltage or current pulse onto a second electrode in a second set of electrodes each time the relaxation oscillator circuit transitions from a charging state to a discharging state; measuring, with the capacitance measurement unit, the mutual capacitance at a node corresponding to the first and second electrodes by measuring a frequency of the relaxation oscillator circuit; and comparing the measured mutual capacitance at the node with a previously measured mutual capacitance corresponding to the node by comparing the frequency to a previously measured frequency corresponding to the node and determining whether the frequency deviates from the previously measured frequency; reporting that the node has been touched if there has been a deviation from the previously measured frequency.