Touch panel testing using mutual capacitor measurements

Abstract

A capacitive touch panel is tested for the presence or absence of short and open circuits in drive and sense lines without the use of a tool that touches the surface of the panel. During a first stage of testing, drive lines of the touch panel are sequentially driven while the remaining drive lines are floated. Sense lines are read to indicate whether a driven drive line is shorted to an adjacent drive line, an open circuit, or coupled to a sense line that is an open circuit. During a second stage of testing, drive lines are driven while alternate sense lines are floated or enabled. The signals on the enabled sense lines are acquired to indicate whether the enabled sense lines are shorted to adjacent sense lines. This second stage can be repeated, switching the roles of the sense lines, to determine the locations of short and/or open circuits.

What is claimed is: 
     
         1 . A capacitive touch panel comprising:
 a plurality of drive lines arranged one next to another;   a plurality of sense lines arranged one next to another across the plurality of drive lines; and   a controller coupled to the plurality of drive lines and the plurality of sense lines, the controller operable to:
 drive at least a first one of the drive lines while floating the remaining drive lines; and 
 read the sense lines to detect a short or an open between the driven drive line and an adjacent ones of the remaining drive lines. 
   
     
     
         2 . The capacitive touch panel as recited in  claim 1 , wherein the controller is further configured to enable at least some of the sense lines while floating others of the sense lines in one or more different combinations and to read the sense lines for detecting a short between two or more of the sense lines. 
     
     
         3 . The capacitive touch panel as recited in  claim 2 , wherein the controller is configured to enable a first set of alternate ones of the sense lines and float a second set of alternate ones of the sense lines. 
     
     
         4 . The capacitive touch panel as recited in  claim 3 , wherein the controller is configured to thereafter enable the second set of alternate ones of the sense lines and floating the first set of alternate ones of the sense lines. 
     
     
         5 . The capacitive touch panel as recited in  claim 4 , wherein the controller is configured to read the sense lines when the first set of alternate ones of the sense lines are enabled and the second set of alternate ones of the sense lines are floating 
     
     
         6 . The capacitive touch panel as recited in  claim 5 , wherein the controller is configured to again read the sense lines when the second set of alternate ones of the sense lines are enabled and the first set of alternate ones of the sense lines are floating. 
     
     
         7 . A process for testing a capacitive touch panel having drive lines arranged one next to another and sense lines arranged one next to another across the drive lines, the process comprising:
 driving at least a first one of the drive lines while floating the remaining drive lines; and   reading the sense lines for detecting at least one of a presence or an absence of a short or an open between the driven drive line and an adjacent ones of the remaining drive lines.   
     
     
         8 . The process as recited in  claim 7 , further comprising enabling at least some of the sense lines while floating others of the sense lines in one or more different combinations and reading the sense lines for detecting a short between two or more of the sense lines. 
     
     
         9 . The process as recited in  claim 8 , wherein enabling at least some of the sense lines while floating others of the sense lines in one or more different combinations comprises enabling a first set of alternate ones of the sense lines and floating a second set of alternate ones of the sense lines. 
     
     
         10 . The process as recited in  claim 9 , wherein enabling at least some of the sense lines while floating others of the sense lines in one or more different combinations further comprises thereafter enabling the second set of alternate ones of the sense lines and floating the first set of alternate ones of the sense lines. 
     
     
         11 . The process as recited in  claim 10 , wherein reading the sense lines for detecting a short between two or more of the sense lines comprises reading the sense lines a first time when the first set of alternate ones of the sense lines are enabled and the second set of alternate ones of the sense lines are floating 
     
     
         12 . The process as recited in  claim 11 , wherein reading the sense lines for detecting a short between two or more of the sense lines comprises reading the sense lines a second time when the second set of alternate ones of the sense lines are enabled and the first set of alternate ones of the sense lines are floating. 
     
     
         13 . The process as recited in  claim 11 , further comprising determining a location of the short between that at least two of the sense line by comparing the signals read from the sense lines the first time with the signals read from the sense lines the second time. 
     
     
         14 . A test system configured for testing a capacitive touch panel having drive lines arranged one next to another, and sense lines arranged one next to another across the drive lines, the test system comprising:
 a memory operable to store one or more modules; and   a processor operable to execute the one or more modules to:
 cause a controller coupled to the plurality of drive lines and the plurality of sense lines to drive at least a first one of the drive lines while floating the remaining drive lines; and 
 cause the controller to read the sense lines to detect at least one of a presence or an absence of a short or an open between the driven drive line and an adjacent ones of the remaining drive lines. 
   
     
     
         15 . The test system as recited in  claim 14 , wherein processor is operable to execute the one or more modules to cause the controller to enable at least some of the sense lines while floating others of the sense lines in one or more different combinations and to read the sense lines for detecting a short between two or more of the sense lines. 
     
     
         16 . The test system as recited in  claim 15 , wherein processor is operable to execute the one or more modules to cause the controller to enable a first set of alternate ones of the sense lines and float a second set of alternate ones of the sense lines. 
     
     
         17 . The test system as recited in  claim 16 , wherein processor is operable to execute the one or more modules to cause the controller to thereafter enable the second set of alternate ones of the sense lines and floating the first set of alternate ones of the sense lines. 
     
     
         18 . The test system as recited in  claim 17 , wherein processor is operable to execute the one or more modules to cause the controller to read the sense lines a first time when the first set of alternate ones of the sense lines are enabled and the second set of alternate ones of the sense lines are floating 
     
     
         19 . The test system as recited in  claim 18 , wherein processor is operable to execute the one or more modules to cause the controller to read the sense lines a second when the second set of alternate ones of the sense lines are enabled and the first set of alternate ones of the sense lines are floating. 
     
     
         20 . The test system as recited in  claim 19 , wherein processor is operable to execute the one or more modules to a location of a short between that at least two of the sense line by comparing the signals read from the sense lines the first time with the signals read from the sense lines the second time.