US 2010/0139991 A1 · Noise Reduction in Capacitive Touch Sensors

Abstract

Noise reduction in a one- or two-dimensional capacitive sensor array is achieved by rejecting and re-acquiring noisy signals. The sensor array is formed of crossed X and Y lines for drive and sense functions respectively, each of the X lines being driven in turn to acquire a full frame of data from the sensor array. A controller actuates the X lines in turn and, for each X line, charge is transferred to charge measurement capacitors connected to respective ones of the Y lines. The controller measures a signal value from a first one of the measurement capacitors, and then tests if that Y signal value has a magnitude lying within an acceptable range. If not, the measurement capacitors are all reset without their signal values being measured, and the controller re-drives the same X line to initiate another charge transfer into the measurement capacitors for that X line. It is then attempted once again to acquire Y signal values for that X line. Noisy signal values are thus rejected, and the sensor re-acquires substitute signal values. This is distinct from the approach of acquiring data and then reprocessing it to remove or suppress noisy data as in the prior art.

Claims9

Dependent claims

A capacitive touch sensor for detecting proximity and location of a body, the sensor comprising:

one or multiple X lines;
a plurality of Y lines each arranged to have a portion thereof adjacent to a portion of each of the X lines to form a plurality of sensing capacitors;
a charge measurement capacitor connected to each Y line;
one or more drive circuits arranged to drive respective ones of the X lines to enable charge transfer from the sensing capacitors associated with that X line to the respective measurement capacitors connected to the Y lines;
and
a controller operable to actuate respective ones of the X lines via their respective drive circuits, and to measure a signal value from each of the measurement capacitors indicative of the amount of charge transferred, the controller being configured such that, when seeking to measure a set of Y signal values from a particular X line, a test is applied to at least the first Y signal value measured which tests if the Y signal value has a magnitude lying outside an acceptable range, wherein responsive to said test, if the Y signal value lies outside the acceptable range, then the same X line is re-actuated to initiate another charge transfer into the measurement capacitors for that X line.

3 more elements

Dependencies are inferred from the claim text.

Noise Reduction in Capacitive Touch Sensors

Life of this patent

Noise Reduction in Capacitive Touch Sensors

Life of this patent

Abstract

Claims9