System and method for determining user input using dual baseline modes

An input device comprising:

• a plurality of capacitive sensor electrodes;
• and
• a processing system coupled to the plurality of capacitive sensor electrodes, the processing system configured to:
• operate the plurality of capacitive sensor electrodes to sense in a sensing region and produce pluralities of preliminary values, each preliminary value corresponding to an individual measured capacitance associated with a corresponding capacitive pixel and obtained using a capacitive sensor electrode of the plurality of capacitive sensor electrodes, the pluralities of preliminary values comprising a first plurality of preliminary values and a second plurality of preliminary values, the second plurality of preliminary values obtained after the first plurality of preliminary values;
• determine information about input in the sensing region based on comparisons of the pluralities of preliminary values with corresponding baseline values of a plurality of baseline values;
• selectively operate in a first mode and a second mode, wherein:
• while operating in the first mode, the processing system individually compares a baseline value of the plurality of baseline values with a corresponding preliminary value of the first plurality of preliminary values, and selectively changes the baseline value by a first amount when the baseline value is substantially different from the corresponding preliminary value to obtain an updated baseline, wherein, in the first mode, the selectively changing the baseline value is performed even when the processing system determines that an input object is in the sensing region;
• and
• while operating in the second mode, the processing system does not selectively change the baseline value by the first amount when the baseline value is different from the corresponding preliminary value and when the processing system determines that the input object is in the sensing region;
• and
• determine a difference between a corresponding baseline value in the updated baseline and a corresponding preliminary value in the second plurality of preliminary values to obtain a plurality of measured values;
• detect, from the plurality of measured values, the input object in the sensing region;
• and
• provide, to an electronic system, positional information of the input object based on detecting the input object,
• wherein the processing system is configured to switch from operating in the first mode to operating in the second mode in response to at least one of a determination that no input objects are in the sensing region and external control signal from a controller.

A method for determining input to and implemented by a capacitive input device of the type having a plurality of capacitive sensor electrodes and configured to sense in a sensing region, the method comprising:

• determining information about input in the sensing region based on comparisons of pluralities of preliminary values with corresponding baseline values of a plurality of baseline values, each preliminary value corresponding to an individual measured capacitance associated with a corresponding capacitive pixel and obtained using a capacitive sensor electrode of the plurality of capacitive sensor electrodes, the pluralities of preliminary values comprising a first plurality of preliminary values and a second plurality of preliminary values, the second plurality of preliminary values obtained after the first plurality of preliminary values;
• and
• selectively operating the capacitive input device in a first mode and a second mode, wherein:
• while operating in the first mode, individually comparing a baseline value of the plurality of baseline values with a corresponding preliminary value of the first plurality of preliminary values, and selectively changing the baseline value by a first amount when the baseline value is different from the corresponding preliminary value, wherein, in the first mode, the selectively changing the baseline value is performed even when an input object is determined to be in the sensing region;
• while operating in the second mode, not selectively changing the baseline value by the first amount when the baseline value is different from the corresponding preliminary value and when an input object is determined to be in the sensing region;
• and
• determining a difference between a corresponding baseline value in the updated baseline and a corresponding preliminary value in the second plurality of preliminary values to obtain a plurality of measured values,
• detecting, from the plurality of measured values, the input object in the sensing region, and
• providing, to an electronic system, positional information of the input object based on detecting the input object,
• wherein the capacitive input device is configured to switch from operating in the first mode to operating in the second mode in response to one of an external signal and a determination that no input objects are in the sensing region.