Capacitive touch system using both self and mutual capacitance

摘要

Systems and methods for determining multiple touch events in a multi-touch sensor system are provided. The system may have a touch sensor including nodes defined by a plurality of electrodes, which may comprise a first and second set. The method may include measuring self capacitance for at least two electrodes, detecting a touched electrode, and measuring the mutual capacitance for only a subset of the nodes (e.g., fewer than all of the nodes and including at least the nodes corresponding to the touched electrodes) resulting in the detection of two or more touched nodes. The self capacitance measurements may be performed on each of the electrodes, and the touched electrodes may comprise electrodes from both the first and second sets. Alternatively, the self capacitance measurements may be performed only on electrodes in the first set, and the touched electrodes may comprise electrodes from only the first set.

主权项

1. A method for determining multiple touch events in a multi-touch sensor system having a touch sensor including a plurality of nodes defined by a plurality of first electrodes arranged in a first layer and second electrodes arranged in a second layer, the method comprising:
performing self capacitance measurements for at least two of the plurality of second electrodes using a capacitance detector; detecting one or more touch events as a result of the performed self capacitance measurements; performing a plurality of mutual capacitance measurements for only a subset of the nodes, wherein the subset is fewer than all of the nodes and includes at least the nodes corresponding to the touch events and wherein a mutual capacitance measurement is performed between first and second electrodes, wherein a pulse drive circuit is connected with one of said first electrodes and the capacitance detector is connected with one of said second electrodes and wherein the pulse drive circuit is synchronized with the capacitance detector, wherein a mutual capacitance measurement is based on charging and/or discharging of a measured capacitance and the pulse drive circuit is synchronized to influence the charging and/or discharging of the measured capacitance; and detecting two or more touch events as a result of the plurality of mutual capacitance measurements.