Baseline recalculation after frequency reconfiguration of a mutual capacitive touch controller

Abstract

Systems and methods are provided that allow a touch sensor, such as a mutual capacitive touch panel, to switch from an operative transmit (TX) frequency at which the mutual capacitive touch panel is driven to an alternative TX frequency. When switching to an alternative TX frequency, an alternative baseline capacitance value corresponding to the alternative TX frequency may be utilized to determine whether a touch event has occurred on the mutual capacitive touch panel. Frame scans can be repeatedly performed at the operative TX frequency and the alternative TX frequency in rapid succession, and an average difference of the frame scans can be calculated and utilized to generate the alternative baseline capacitance value which may be insensitive to sudden ambient changes and moving touch events affecting the mutual touch capacitive panel.

What is claimed is: 
     
         1 . An integrated circuit comprising:
 processing circuitry;   memory; and   a digital touch subsystem configured to:
 determine a first plurality of baseline capacitance values of a capacitive touch panel based upon a first scanning frequency; 
 repeat, a number of times:
 a first frame scan of the capacitive touch panel at the first scanning frequency and a second frame scan of the capacitive touch panel at a second scanning frequency; and 
 determine differences in capacitance values of the capacitive touch panel between the first frame scan and the second frame scan; 
 
 determine composite differences in capacitance values of the capacitive touch panel between the first frame scans and the second frame scans; and 
 generate a second plurality of baseline capacitance values of the capacitive touch screen corresponding to the second scanning frequency by adding the determined composite differences in capacitance values of the capacitive touch panel to the first plurality of baseline capacitance values of the capacitive touch screen corresponding to the first scanning frequency. 
   
     
     
         2 . The integrated circuit of  claim 1 , the digital touch subsystem further configured to, for at least some of the number of times:
 detect noise associated with the first frame scan and the second frame scan; and   discard the determined difference in capacitance values of the capacitive touch screen when the detected noise exceeds a threshold.   
     
     
         3 . The integrated circuit of  claim 1 , the digital touch subsystem further configured to use the second scanning frequency instead of the first scanning frequency upon detecting noise on the first scanning frequency that exceeds a threshold. 
     
     
         4 . The integrated circuit of  claim 3 , the digital touch subsystem further configured to use the second plurality of baseline capacitances of the capacitive touch screen value instead of the first plurality of baseline capacitance values. 
     
     
         5 . The integrated circuit of  claim 3 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs prior to the detection of the noise on the first scanning frequency. 
     
     
         6 . The integrated circuit of  claim 3 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs subsequent to the detection of the noise on the first scanning frequency. 
     
     
         7 . The integrated circuit of  claim 1 , further comprising a host processor. 
     
     
         8 . The integrated circuit of  claim 1 , wherein the digital touch subsystem further comprises at least one of:
 a wireless interface that communicatively couples the integrated circuit to the capacitive touch panel; or   a wired connection to the capacitive touch panel.   
     
     
         9 . An integrated circuit comprising:
 processing circuitry;   memory; and   a digital touch subsystem configured to:
 determine a first plurality of baseline capacitance values of a capacitive touch panel based upon a first scanning frequency; 
 repeat, a number of times:
 a first frame scan of the capacitive touch panel at the first scanning frequency and a second frame scan of the capacitive touch panel at a second scanning frequency; and 
 determine differences in capacitance values of the capacitive touch panel between the first frame scan and the second frame scan; and 
 
 generate a second plurality of baseline capacitance values of the capacitive touch screen corresponding to the second scanning frequency based upon the first plurality of baseline capacitance values and at least some of the determined differences in capacitance values. 
   
     
     
         10 . The integrated circuit of  claim 9 , the digital touch subsystem further configured to, for at least some of the number of times:
 detect noise associated with the first frame scan and the second frame scan; and   discard the determined difference in capacitance values of the capacitive touch screen when the detected noise exceeds a threshold.   
     
     
         11 . The integrated circuit of  claim 9 , the digital touch subsystem further configured to:
 use the second scanning frequency instead of the first scanning frequency upon detecting noise on the first scanning frequency that exceeds a threshold; and   use the second plurality of baseline capacitances of the capacitive touch screen value instead of the first plurality of baseline capacitance values.   
     
     
         12 . The integrated circuit of  claim 11 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs prior to the detection of the noise on the first scanning frequency. 
     
     
         13 . The integrated circuit of  claim 11 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs subsequent to the detection of the noise on the first scanning frequency. 
     
     
         14 . The integrated circuit of  claim 9 , further comprising a host processor. 
     
     
         15 . The integrated circuit of  claim 9 , wherein the digital touch subsystem further comprises at least one of:
 a wireless interface that communicatively couples the integrated circuit to the capacitive touch panel; or   a wired connection to the capacitive touch panel.   
     
     
         16 . A method comprising:
 determine a first plurality of baseline capacitance values of a capacitive touch panel based upon a first scanning frequency;   repeat, a number of times:
 a first frame scan of the capacitive touch panel at the first scanning frequency and a second frame scan of the capacitive touch panel at a second scanning frequency; and 
 determine differences in capacitance values of the capacitive touch panel between the first frame scan and the second frame scan; and 
   generate a second plurality of baseline capacitance values of the capacitive touch screen corresponding to the second scanning frequency based upon the first plurality of baseline capacitance values and at least some of the determined differences in capacitance values.   
     
     
         17 . The method of  claim 16 , further comprising, for at least some of the number of times:
 detecting noise associated with the first frame scan and the second frame scan; and   discarding the determined difference in capacitance values of the capacitive touch screen when the detected noise exceeds a threshold.   
     
     
         18 . The method of  claim 16 , further comprising:
 using the second scanning frequency instead of the first scanning frequency upon detecting noise on the first scanning frequency that exceeds a threshold; and   using the second plurality of baseline capacitances of the capacitive touch screen value instead of the first plurality of baseline capacitance values.   
     
     
         19 . The method of  claim 18 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs prior to the detection of the noise on the first scanning frequency. 
     
     
         20 . The method of  claim 18 , wherein the generation of the second plurality of baseline capacitance values of the capacitive touch screen occurs subsequent to the detection of the noise on the first scanning frequency.