Abstract:
The present invention discloses a control device for a touch panel. The touch panel comprises a plurality of X-directional sensing lines and a plurality of Y-directional sensing lines arranged in a staggered manner. The control device comprises a clock generation circuit, a selection module, an analog to digital conversion circuit, and a control unit. The selection module selects sensing lines to be measured from the X-directional sensing lines and Y-directional sensing lines. The control unit controls the operation mode of the analog to digital conversion circuit. The analog to digital conversion circuit outputs an n-bit digital signal when it operates in a normal mode, and outputs an m-bit digital signal when it operates in a detecting mode, wherein n&gt;m. According to the control device of the present invention, valid data is output in the presence of noise.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention The present invention relates to a control device for a touch panel and a signal processing method thereof. 
         [0002]    2. Description of the Related Art 
         [0003]    Touch panels are widely applied in a variety of fields such as home appliances, communication devices and electronic information devices. The touch panel is often applied in input interfaces of personal digital assistants (PDAs), electronic products and game consoles. The current trend of integrating a touch panel and a display allows a user to select an icon displayed on the panel by using a finger or a touch pen, so that the PDA, the electronic product, or the game console executes a desired is function. The touch panel may also be applied in a public information inquiry system, so that the user can operate the system more efficiently. 
         [0004]      FIG. 1  is a schematic view of a conventional touch input device  10 . The touch input device  10  includes a touch panel  12  and a control device  100 . The touch panel  12  includes a plurality of X-directional sensing lines X 1  to Xm, and a plurality of Y-directional sensing lines Y 1  to Yn. Referring to  FIG. 1 , the plurality of X-directional sensing lines X 1  to Xm and the plurality of Y-directional sensing lines Y 1  to Yn are arranged in a staggered manner. A plurality of rhombus grids  11  are disposed between the X-directional sensing lines X 1  to Xm and the Y-directional sensing lines Y 1  to Yn. When a touching tool such as a finger or a touch pen contacts the touch panel  12 , the capacitive value between rhombus grids  11  in the panel and the touching tool will be changed due to the touching tool. 
         [0005]    The control device  100  includes a selection module  14 , an analog to digital conversion circuit  16 , and a processing unit  18 . The selection module  24  couples with the touch panel  12  and selects the sensing lines L 1  to Ln from the X-directional sensing lines X 1  to Xm and the Y-directional sensing lines Y 1  to Yn. The analog to digital conversion circuit  16  converts the voltages of the sensing lines L 1  to Ln to an n-bit digital signal. The n-bit digital signal represents the touching condition of the sensing lines to be measured. The processing unit  18  receives the n-bit digital signal converted by the analog to digital conversion circuit  16  and figures out the touching condition of the sensing lines through an algorithm. The touching condition includes data of the touching position and the touching area of the touching tool. 
         [0006]    However, the signal received by the processing unit  18  may be a clear touching signal or a signal with noise. Thus, the processing unit  18  requires a complex filter for removing the noise. In order to simplify the is internal circuitry of the processing unit  18  and to provide an efficient digital signal, it is necessary to provide a control device for a touch panel and a signal processing method thereof to filter the noise from the output data. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention discloses a control device for a touch panel. The touch panel comprises a plurality of X-directional sensing lines and a plurality of Y-directional sensing lines. The X-directional sensing lines and the Y-directional sensing lines are arranged in a staggered manner. The control device of the present invention comprises a selection module, an analog to digital conversion circuit, and a control unit. The selection module selects the sensing lines to be measured from the X-directional sensing lines and the Y-directional sensing lines. The analog to digital conversion circuit couples with the selection module for receiving voltages of the sensing lines to be measured. In accordance with different operation modes, the analog to digital conversion circuit converts the voltages into different bits of a sequence digital signal. When the analog to digital conversion circuit operates in a normal mode, the analog to digital conversion circuit outputs an n-bit digital signal. When the analog to digital conversion circuit operates in a detecting mode, the analog to digital conversion circuit outputs an m-bit digital signal, wherein n&gt;m. The control unit is configured for controlling the analog to digital conversion circuit to operate either in the normal mode or in the detecting mode. 
         [0008]    The present invention also discloses a signal processing method for a touch panel. The signal processing method of the present invention comprises the following steps: selecting a plurality of sensing lines to be measured from the X-directional sensing lines and the Y-directional sensing lines; determining a threshold value and a bit number m to be measured; converting voltages of the sensing lines to be measured in accordance with the m-bit and outputting an m-bit digital signal; detecting the converted m-bit digital signal and a difference between the m-bit digital is signal and a predetermined m-bit digital signal, when the converted m-bit digital signal and the predetermined m-bit digital signal have the same value to accumulate a counting value; and converting voltages of the sensing lines to be measured to an n-bit digital signal when the counting value is greater than or equal to the threshold value, wherein n&gt;m. 
         [0009]    The foregoing has outlined rather broadly the features and technical benefits of the disclosure in order that the detailed description of the invention that follows may be better understood. Additional features and benefits of the invention will be described hereinafter, and form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention will be described according to the appended drawings in which: 
           [0011]      FIG. 1  is a schematic view of a conventional touch input device; 
           [0012]      FIG. 2  is a schematic view of a touch input device in accordance with one embodiment of the present invention; 
           [0013]      FIG. 3  is a schematic block diagram of a detail circuit of the control unit in accordance with one embodiment of the present invention; 
           [0014]      FIG. 4  is a schematic view of another touch input device in accordance with one embodiment of the present invention; and 
           [0015]      FIG. 5  is a schematic view of an operation mode of the touch input device in accordance with one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The present invention is directed to a control device and a signal is processing method for a touch panel. In order to make the present invention completely comprehensible, detailed steps and structures are provided in the following description. Obviously, implementation of the present invention does not limit special details known by persons skilled in the art. In addition, known structures and steps are not described in detail, so as not to unnecessarily limit the present invention. Preferred embodiments of the present invention will be described below in detail. However, in addition to the detailed description, the present invention may also be widely implemented in other embodiments. The scope of the present invention is not limited to the detailed description, and is defined by the claims. 
         [0017]      FIG. 2  illustrates a schematic view of a touch input device  20  in accordance with an embodiment of the present invention. The touch input device  20  comprises a touch panel  22  and a control device  200 . The control device  200  is configured for providing a driving signal to the touch panel  22  and detecting its touch condition. The touch panel  22  comprises a plurality of X-directional sensing lines X 1  to X 8  and a plurality of Y-directional sensing lines Y 1  to Y 8 . Referring to  FIG. 2 , the X-directional sensing lines X 1  to X 8  and the Y-directional sensing lines Y 1  to Y 8  are arranged in a staggered manner. A plurality of rhombus grids  21  are disposed between the X-directional sensing lines X 1  to X 8  and the Y-directional sensing lines Y 1  to Y 8 . When every grid on the X-directional sensing lines X 1  to X 8  and the Y-directional sensing lines Y 1  to Y 8  is electrically conducted, a touching tool such as a finger or a touch pen contacts the touch panel  22  such that the capacitive value between rhombus grids  21  in the panel and the touching tool will be changed due to the touching tool. 
         [0018]    is Referring  FIG. 2 , the control device  200  includes a selection module  24 , an analog to digital conversion circuit  26 , a control unit  28 , and a control unit  30 . The selection module  24  couples with the touch panel  22 . During touch detection of the touch panel  22 , the driving signals will be applied to the X-directional sensing lines X 1  to X 8  and the Y-directional sensing lines Y 1  to Y 8 . The selection module  24  selects a plurality of sensing lines L 1  to L n  to be measured from the X-directional sensing lines X 1  to X 8  and the Y-directional sensing lines Y 1  to Y 8  for detecting the capacitive variation of the sensing lines. 
         [0019]    As shown in  FIG. 2 , the analog to digital conversion circuit  26  couples with the selection module  24 . The analog to digital conversion circuit  26  receives the voltages of the sensing lines L 1  to L n  to be measured and converts the voltages into different bits of a sequence digital signal in accordance with different operation modes. The analog to digital conversion circuit  26  of an embodiment of the present invention can include a successive approximation register (SAR) (not shown). The SAR controls the analog to digital conversion circuit  26  bit by bit to output in accordance with a binary search algorithm. The analog to digital conversion circuit  26  can be operated either in a normal mode or a detecting mode. When the analog to digital conversion circuit  26  operates in a normal mode, the analog to digital conversion circuit  26  outputs an n-bit digital signal to the processing unit  30 . When the analog to digital conversion circuit  26  operates in a detecting mode, the analog to digital conversion circuit  26  outputs an m-bit digital signal to the control unit  28 . The bit number of the m-bit digital signal is smaller than the bit number of the n-bit digital signal. 
         [0020]    The operation mode of the analog to digital conversion circuit  26  is controlled by a control unit  28 .  FIG. 3  illustrates a detail circuit of the control unit  28  in accordance with an embodiment of the present invention. Referring to  FIG. 3 , the control unit  28  includes registers  281 ,  282 , a detecting unit  284 , a counter  286  and a comparing unit  288 . The first is register  281  is configured for recording a predetermined m-bit digital signal. The second register  282  is configured for recording a threshold value (TH). The detecting unit  284  is configured for detecting the m-bit digital signal converted by the analog to digital conversion circuit  26  in the detecting mode and comparing the m-bit digital signal to be measured with the predetermined m-bit digital signal to generate a comparing signal (cmp). The counter  286  is coupled with the detecting unit  284  and configured for accumulating a counting value (CNT) in accordance with the comparing signal cmp. The comparing unit  288  is coupled with the counter  286  and configured for comparing the counting value (CNT) and the threshold (TH). When the counting value (CNT) is greater than or equal to the threshold (TH), the comparing unit  286  transmits a control signal (CTL) to control the analog to digital conversion circuit  26  to operate in the normal mode. 
         [0021]    In one embodiment of the present invention, the touch input device  20  is operated as illustrated in  FIG. 4  and  FIG. 5 . Referring to  FIG. 4 , during the first scan in a touch panel, if the selection module  24  selects sensing lines X 3  and X 4  to be measured from the X-directional sensing lines X 1  to X 8 , the analog to digital conversion circuit  26  will convert the voltages of the sensing lines X 3  and X 4  to generate an 8-bit digital signal D 0  to D 7 . D o  is the least significant bit (LSB) and D 7  is the most significant bit (MSB). However, the 8-bit digital signal may be a clear touching signal or a signal with noise. In order to avoid unnecessary processing by the processing unit  30  for the capacitive variation due to the noise, the analog to digital conversion circuit  26  is initially operated in a detecting mode to output 2-bit digital signals D 7,1  and D 6,1 . The analog to digital conversion circuit  26  of the present embodiment can output, but is not limited to outputting, the 2-bit digital signals. In other words, when the analog to digital conversion circuit  26  is operated in the detecting mode, the bit number outputted by the analog to digital conversion circuit  26  can be predetermined in accordance with different designs and is not limited to the MSB digital signals. 
         [0022]    is In the present embodiment, the 2-bit digital signals D 7,1  and D 6,1  will be recorded in the first register  281 . Consequently, the analog to digital conversion circuit  26  continuously converts the voltages of the sensing lines X 3  and X 4  to 2-bit digital signals D  7, 2  and D  6, 2  . Since the noise interferes with the signal, the value of the digital signals D 7,2  and D 6,2  is different from that of the digital signals D 7,1  and D 6,1 . Thus, after the detecting unit  282  compares the digital signals D 7,2  and D 6,2  with digital signals D 7 ,1  and D  6  ,  1  , the detecting unit  282  will generate a comparing signal (cmp) with a low level. The counter  286  is not activated in accordance with the low-level comparing signal (cmp). 
         [0023]    The analog to digital conversion circuit  26  continuously converts the voltages of the sensing lines X 3  and X 4  to 2-bit digital signals D 7,3  and D  6,3 . Since the value of the digital signals D 7,3  and D 6,3  is the same as that of the digital signals D 7,1  and D 6,1 , the detecting unit  282  will generate a comparing signal (cmp) with a high level. The counter  286  will accumulate a counting value in accordance with the high-level comparing signal (cmp). 
         [0024]    Similarly, the analog to digital conversion circuit  26  continuously converts the voltages of the sensing lines X 3  and X 4 . After the detecting unit  282  compares the converted digital signals with the digital signals D 7,1  and D 6,1 , the level of the comparing signal (cmp) is continuously updated. The comparing unit  288  determines whether the counting value (CNT) is accumulated in accordance with the level of the comparing signal (cmp). When the counting value (CNT) is greater than or equal to the threshold value (e.g.  3 ) registered by the second register  282 , the comparing D) unit  286  transmits a control signal (CTL) to switch the analog to digital conversion circuit  26  to operate in the normal mode from the detecting mode. Therefore, the analog to digital conversion circuit  26  will continuously convert the voltages of the sensing lines X  3  and X 4  to a 2-bit digital signal. The entire 8-bit digital signal D 0  to D 7  will be transmitted is to the processing unit  30  for further processing. Since the control device  200  of the present invention can adjust the outputted bit number of the analog to digital conversion circuit  26  and the threshold value, the present invention can effectively remove the noise and ensure the signals received by the processing unit  30  to be clear touch signals. 
         [0025]    Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims. For example, many of the processes discussed above can be implemented in different methodologies and replaced by other processes, or a combination thereof. 
         [0026]    Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, and composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.