High-Accuracy Touch Positioning for Touch Panels

Abstract

Control circuitry for a touch panel includes a touch panel interface, a memory comprising touch positioning logic, and a controller in communication with the memory and the touch panel interface. The controller is operable, when the touch positioning logic is executed, to perform selected processing of the touch panel, including scanning a touch panel and determining a touch panel blob resulting from a touch, obtaining blob characteristics of the touch panel blob, and determining a position of the blob relative to the touch panel based on the blob characteristics. The blob characteristics can be adjusted to more accurately position the blob in circumstances where the blob is located near the edge of the touch panel, is in close proximity to another blob, or when the touch panel has variation in the received signal noise.

1 . Control circuitry for a touch panel, the control circuitry comprising:
 a touch panel interface;   a memory comprising touch positioning logic; and   a controller in communication with the memory and the touch panel interface, the controller configured, when the touch positioning logic is executed, to:
 scan a touch panel; 
 determine a first touch panel blob and a second touch panel blob from the scan; 
 determine that the first touch panel blob and the second touch panel blob share a common member pixel; 
 apportion capacitance of the common member pixel between the first touch panel blob and the second touch panel blob; and 
 determine a position of the first touch panel blob, the second touch panel blob, or both, taking into consideration the capacitance that was apportioned between the first touch panel blob and the second touch panel blob. 
   
     
     
         2 . The control circuitry of  claim 1 , where the controller is configured to:
 find a boundary between the first touch panel blob and the second touch panel blob;   determine that the boundary bisects the capacitance of the common member pixel into a first amount of capacitance and a second amount of capacitance;   apportion the first amount of capacitance to the first touch panel blob; and   apportion the second amount of capacitance to the second touch panel blob.   
     
     
         3 . The control circuitry of  claim 2 , where the controller is configured to determine the boundary as a vertical line. 
     
     
         4 . The control circuitry of  claim 2 , where the controller is configured to determine the boundary as a horizontal line. 
     
     
         5 . The control circuitry of  claim 1 , where the position comprises a position for the first touch panel blob, determined from characteristics of both the first touch panel blob and the second touch panel blob. 
     
     
         6 . The control circuitry of  claim 1 , where the controller is configured to report the position to a host processor in communication with the controller. 
     
     
         7 . The control circuitry of  claim 1 , where the controller is further configured to determine that the first touch panel blob and the second touch panel blob share the common member pixel by determining the common member pixel based on a member-identifying threshold. 
     
     
         8 . The control circuitry of  claim 7 , where the controller is further configured to determine the member-identifying threshold using a noise floor estimate of the touch panel determined from a prior scan of the touch panel. 
     
     
         9 . The control circuitry of  claim 1 , where the controller is further configured to:
 determine a first peak pixel of the first touch panel blob that exceeds a touch-reporting threshold;   determine a second peak pixel of the second touch panel blob that exceeds the touch-reporting threshold;   determine a first position of the first touch panel blob relative to the touch panel based on the first peak pixel and a first amount of capacitance apportioned to the first touch panel blob; and   determine a second position of the second touch panel blob relative to the touch panel based on the second peak pixel and a second amount of capacitance apportioned to the second touch panel blob.   
     
     
         10 . The control circuitry of  claim 9 , where the controller is further configured to determine that the first touch panel blob and the second touch panel blob share the common member pixel by:
 analyzing a first window around the first peak pixel that includes the common member pixel; and   analyzing a second window around the second peak pixel that includes the common member pixel.   
     
     
         11 . The control circuitry of  claim 1 , where the controller is further configured to:
 obtain a blob characteristic for the first touch panel blob; and   determine a position of the first touch panel blob relative to the touch panel based on the blob characteristic.   
     
     
         12 . The control circuitry of  claim 11 , where the controller is further configured to adjust the blob characteristic of the first touch panel blob when the touch panel blob is positioned near an edge of the touch panel by adding a virtual member pixel to the first touch panel blob. 
     
     
         13 . A method comprising:
 scanning a touch panel;   determining a first touch panel blob and a second touch panel blob from the scan;   determining that the first touch panel blob and the second touch panel blob share a common member pixel;   apportioning capacitance of the common member pixel between the first touch panel blob and the second touch panel blob;   determining a first position for the first touch panel blob, taking into consideration the capacitance that was apportioned; and   determining a second position for the second touch panel blob, taking into consideration the capacitance that was apportioned.   
     
     
         14 . The method of  claim 13 , further comprising:
 finding a boundary between the first touch panel blob and the second touch panel blob; and   determining that the boundary divides the capacitance of the common member pixel into a first amount of capacitance and a second amount of capacitance; and   where apportioning capacitance of the common member pixel between the first touch panel blob and the second touch panel blob comprises:
 apportioning the first amount of capacitance to the first touch panel blob; and 
 apportioning the second amount of capacitance to the second touch panel blob. 
   
     
     
         15 . The method of  claim 14 , further comprising:
 determining a first peak pixel of the first touch panel blob that exceeds a touch-reporting threshold;   determining a second peak pixel of the second touch panel blob that exceeds the touch-reporting threshold;   determining a first position of the first touch panel blob relative to the touch panel based on the first peak pixel and the first amount of capacitance; and   determining a second position of the second touch panel blob relative to the touch panel based on the second peak pixel and the second amount of capacitance.   
     
     
         16 . The method of  claim 13 , further comprising:
 obtaining a first blob characteristic for the first touch panel blob;   obtaining a second blob characteristic for the second touch panel blob;   determining a first position of the first touch panel blob relative to the touch panel based on the first blob characteristic; and   determining a second position of the second touch panel blob relative to the touch panel based on the second blob characteristic.   
     
     
         17 . A product comprising:
 a machine-readable medium other than a transitory signal; and   instructions stored on the machine-readable medium, the instructions are configured to, when executed by a processor:
 scan a touch panel; 
 determine a first touch panel blob and a second touch panel blob from the scan; 
 responsive to a member-identifying threshold, determine that the first touch panel blob and the second touch panel blob share a common member pixel; 
 apportion capacitance of the common member pixel between the first touch panel blob and the second touch panel blob; and 
 determine a first position for the first touch panel blob responsive to a first amount of the capacitance apportioned to the first touch panel blob. 
   
     
     
         18 . The product of  claim 17 , where the instructions are further configured to determine the member-identifying threshold using a noise floor estimate of the touch panel determined from a prior scan of the touch panel. 
     
     
         19 . The product of  claim 17 , where the instructions are configured to determine the first position for the first touch panel blob by calculating a centroid of the first touch panel blob using the first amount of capacitance apportioned to the first touch panel blob. 
     
     
         20 . The product of  claim 17 , where the instructions are further configured to determine a second position for the second touch panel blob responsive to a second amount of capacitance apportioned to the second touch panel blob.