Detection of a conductive object during an initialization process of a touch-sensing device

Abstract

A method and apparatus determine a first capacitance value that represents a first capacitance of a first sense element and determine a second capacitance value that represents a second capacitance of a second sense element, where the second capacitance value is responsive to a conductive object proximate to the second sense element. The method and apparatus determine a difference value that represents a difference between the first capacitance value and the second capacitance value and detect a presence of the conductive object responsive to the difference meeting or exceeding a threshold difference value.

What is claimed is: 
     
         1 . A method comprising:
 determining a first capacitance value that represents a first capacitance of a first sense element;   determining a second capacitance value that represents a second capacitance of a second sense element, wherein the second capacitance value is responsive to a conductive object proximate to the second sense element;   determining a difference value that represents a difference between the first capacitance value and the second capacitance value; and   detecting a presence of the conductive object responsive to the difference meeting or exceeding a threshold difference value.   
     
     
         2 . The method of  claim 1 , wherein the determining of the first capacitance value includes the first capacitance value not being responsive to the conductive object when the conductive object is proximate to one or more materials that isolate the first sense element from conductive objects. 
     
     
         3 . The method of  claim 2 , wherein the determining of the first capacitance value and the second capacitance value includes the first capacitance value and the second capacitance value being responsive to an effect of one or more environmental attributes of an environment of the first sense element and the second sense element. 
     
     
         4 . The method of  claim 3 , wherein the one or more environmental attributes include one or more of a temperature of the environment and a humidity of the environment. 
     
     
         5 . The method of  claim 3 , wherein the determining of the difference value removes at least a portion of the effect of the one or more environmental attributes on the first capacitance value and the second capacitance value. 
     
     
         6 . The method of  claim 1 , wherein the first capacitance value and the second capacitance value are equivalently responsive to an effect of one or more environmental attributes of an environment of the first sense element and the second sense element. 
     
     
         7 . The method of  claim 1 , wherein the first capacitance of the first sense element is a self capacitance and the second capacitance of the second sense element is a self capacitance. 
     
     
         8 . The method of  claim 1 , wherein the first capacitance of the first sense element is a mutual capacitance and the second capacitance of the second sense element is a mutual capacitance. 
     
     
         9 . The method of  claim 1 , further comprising storing, in a memory device, the first capacitance value as a baseline capacitance value for the second sense element. 
     
     
         10 . An apparatus comprising:
 a substrate;   a plurality of sense elements coupled to the substrate, each of the plurality of sense elements configured to be coupled with a processing circuit, wherein,
 a capacitance of a first sense element of the plurality of sense elements is responsive to one or more environmental attributes, and a conductive object proximate to the first sense element, and 
 a capacitance of a second sense element of the plurality of sense elements is responsive to the one or more environmental attributes, and is not responsive to the conductive object proximate to the second sense element. 
   
     
     
         11 . The apparatus of  claim 10 , wherein the one or more environmental attributes include at least one of a temperature and a humidity of an environment of the first sense element and the second sense element. 
     
     
         12 . The apparatus of  claim 10 , wherein the first sense element and the second sense element comprise physical attributes such that the capacitance of the first sense element and the capacitance of the second sense element are equivalently responsive to the one or more environmental attributes. 
     
     
         13 . The apparatus of  claim 10 , wherein the capacitance of the first sense element is mutual capacitance and the capacitance of the second sense element is mutual capacitance. 
     
     
         14 . The apparatus of  claim 10 , further comprising a material arranged relative to the second sense element such that the second sense element is not responsive to the conductive object proximate to the second sense element. 
     
     
         15 . The apparatus of  claim 10 , wherein the first sense element is disposed on first side of the substrate and the second sense element is disposed on an opposite side of the substrate. 
     
     
         16 . The apparatus of  claim 10 , wherein the processing circuit is coupled to the substrate, wherein the processing circuit is configured to:
 determine the capacitance of the first sense element,   determine the capacitance of the second sense element,   determine a difference between the capacitance of the first sense element and the capacitance of the second sense element, and   detect a presence of the conductive object responsive to the difference meeting or exceeding a threshold value.   
     
     
         17 . An electronic system comprising:
 a substrate;   a processing circuit;   a memory device;   a plurality of sense elements, each of the plurality of sense elements coupled with a processing circuit, wherein,   a capacitance of a first sense element of the plurality of sense elements is responsive to one or more environmental attributes, and a conductive object proximate to the first sense element, and   a capacitance of a second sense element of the plurality of sense elements is responsive to the one or more environmental attributes, and is not responsive to the conductive object proximate to the second sense element.   
     
     
         18 . The electronic system of  claim 17 , wherein the processing circuit is configured to measure the capacitance of the first sense element, measure the capacitance of the second sense element, calculate a difference between the capacitance of the first sense element and the capacitance of the second sense element, and detect a presence of the conductive object responsive to the calculated difference meeting or exceeding a threshold value. 
     
     
         19 . The electronic system of  claim 17 , further comprising a material arranged to isolate the first sense element from capacitively coupling with the conductive object proximate to the first sense element. 
     
     
         20 . The electronic system of  claim 17 , wherein the first sense element is disposed on first side of the substrate and the second sense element is disposed on an opposite side of the substrate.