Abstract:
A method for detecting noise of a touch panel and performing signal control is provided, where the method may determine how many cycles of frame data are influenced by noise, may determine whether the frame data is influenced by noise by determining whether a number of cycles influenced by noise is greater than a first threshold value or not, and may determine whether a number of continuous frame data determined to be influenced by noise is greater than a second threshold value to generate a determination result. Finally, the method may determine whether to adjust a frequency of the transmitting signals according to the determination result.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a touch panel, and more particularly, to a method for accurately detecting touch panel noise and performing signal control. 
     2. Description of the Prior Art 
     Current production requirements of a capacitive touch panel have strict tests for accuracy and jitter. Designers are encouraged to raise a signal to noise ratio (SNR) to satisfy these requirements, where the SNR can be improved by increasing the signals or by decreasing the noise. In a touch controller of the capacitive touch panel, the main noise comes from elements outside the panel such as the liquid crystal module (LCM), power source and light source. How to accurately detect and lower the noise becomes very important. 
     SUMMARY OF THE INVENTION 
     It is therefore an objective of the present invention to provide a method for detecting touch panel noise and performing signal control, and an associated controller, which can use a simple algorithm to accurately detect and efficiently lower the noise of the touch panel. 
     According to one embodiment of the present invention, a method for detecting touch panel noise and performing signal control is provided, wherein the touch panel comprises a plurality of sensing lines and a plurality of driving lines, and the sensing lines and the driving lines are intersected, and the method comprises: (a) sequentially transmitting a plurality of transmitting signals to the driving lines of the touch panel, respectively; (b) receiving data of a plurality of cycles, where data of one cycle is digital data of a plurality of receiving signals from the sensing lines when one transmitting signal is enabled and inputted into its corresponding driving line, and the data of the plurality of cycles form one frame data of the touch panel; (c) determining how many cycles are influenced by noise; (d) determining whether the frame data is influenced by noise by determining whether a number of cycles influenced by noise is greater than a first threshold value or not, where when the number of cycles influenced by noise is greater than the first threshold value, the frame data is determined to be influenced by noise; (e) repeating steps (a)-(d) to determine whether a number of continuous frame data determined to be influenced by noise is greater than a second threshold value to generate a determination result; and (f) adjusting a frequency of the transmitting signals according to the determination result. 
     According to another embodiment of the present invention, a controller of a touch panel is provided, where the touch panel comprises a plurality of sensing lines and a plurality of driving lines, and the sensing lines and the driving lines are intersected, and the controller comprises a micro-processor and a program code stored in a storage device of the controller. When the program code is executed by the micro-processor, the program code executes the following steps: (a) sequentially transmitting a plurality of transmitting signals to the driving lines of the touch panel, respectively; (b) receiving data of a plurality of cycles, where data of one cycle is digital data of a plurality of receiving signals from the sensing lines when one transmitting signal is enabled and inputted into its corresponding driving line, and the data of the plurality of cycles form one frame data of the touch panel; (c) determining how many cycles are influenced by noise; (d) determining whether the frame data is influenced by noise by determining whether a number of cycles influenced by noise is greater than a first threshold value or not, where when the number of cycles influenced by noise is greater than the first threshold value, the frame data is determined to be influenced by noise; (e) repeating steps (a)-(d) to determine whether a number of continuous frame data determined to be influenced by noise is greater than a second threshold value to generate a determination result; and (f) adjusting a frequency of the transmitting signals according to the determination result. 
     These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a touch panel according to one embodiment of the present invention. 
         FIG. 2  is an example of a plurality of cycles of data of the receiving signals R 1 -R 11  corresponding to the transmitting signals T 1 -T 19 . 
         FIG. 3  is a flowchart of a method for accurately detecting touch panel noise and performing signal control according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include” and “comprise” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. Also, the term “couple” is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. 
     Please refer to  FIG. 1 , which illustrates a touch panel  100  according to one embodiment of the present invention. In this embodiment, the touch panel  100  is a capacitive touch panel, and the touch panel  100  includes a plurality of driving lines and a plurality of sensing lines (in this embodiment there are nineteen driving lines DL 1 -DL 19  and eleven sensing lines SL 1 -SL 11 ) and a controller  110 , where the controller  110  includes a micro-processor  112  and a program code  114  stored in a storage device of the controller  110 . The driving lines DL 1 -DL 19  and the sensing lines SL 1 -SL 11  are intersected to form an array, the controller  110  sequentially transmits a plurality of transmitting signals T 1 -T 19  into the driving lines DL 1 -DL 19  (the enabling periods of the transmitting signals T 1 -T 19  are not overlapped), respectively, and during each of the enabling periods of the transmitting signals T 1 -T 19 , the controller  110  receives a plurality of receiving signals R 1 -R 11  from the sensing lines SL 1 -SL 11  to determine whether one or more touch points are on the touch panel  100  or not. 
     Please refer to  FIG. 2 , which is an example of a plurality of cycles of data of the receiving signals R 1 -R 11  corresponding to the transmitting signals T 1 -T 19 . The data shown in  FIG. 2  is digital data: analog-to-digital converters (not shown) which are built in the controller  110  convert the analog receiving signals R 1 -R 11  into digital data. As shown in  FIG. 2 , when the transmitting signal T 1  is enabled and inputted into the driving line DL 1 , the controller  100  receives the receiving signals R 1 -R 11  to generate data of cycle  1 ; then the transmitting signal T 2  is enabled and inputted into the driving line DL 2 , the controller  100  receives the receiving signals R 1 -R 11  to generate data of cycle  2 , . . . and so on. The whole data (data of the cycles  1 - 19 ) shown in  FIG. 2  is frame data, and this frame data corresponds to a plurality of intersection regions of the driving lines DL 1 -DL 19  and the sensing lines SL 1 -SL 11 . The data shown in  FIG. 2  can be used to determine whether one or more touch points is/are applied on the touch panel  100 , and to determine the position(s) of the touch point(s). 
     Ideally, when there is no touch point on the touch panel  100 , the data shown in  FIG. 2  should be “0”; and when there is a touch point on the touch panel  100 , the value of its corresponding data shown in  FIG. 2  should be large (e.g. 50-250). Because of noise caused by the LCM, power source and/or light source, however, even when there is no touch point on the touch panel  100 , the data shown in  FIG. 2  will not all be equal to “0”. 
     Please refer to  FIG. 3 , which is a flowchart of a method for accurately detecting noise of the touch panel  100  and performing signal control according to one embodiment of the present invention. The flow shown in  FIG. 3  is executed by using the micro-processor  112  to execute the program code  114 . Referring to  FIG. 3 , the flow is described as follows. 
     In Step  300 , the flow starts. In Step  302 , a parameter n is set to be “0”. In Step  304 , for a current cycle (e.g. cycle  1  shown in  FIG. 2 ), a maximum value and a minimum value of the cycle are found. In Step  306 , it is determined whether the minimum value is greater than a threshold value A or not (in this embodiment, A can be 3 or 4): if the minimum value is greater than A, the flow enters Step  308 ; otherwise, the flow enters Step  312 . In Step  308 , it is determined whether a difference between the maximum value and the minimum value is less than a threshold value B or not (in this embodiment, B can be 10): if the difference is less than B, the flow enters Step  310 ; otherwise, the flow enters Step  312 . In Step  310 , the value of the parameter n is increased by an increment of 1. In Step  312 , it is determined whether a next cycle exists: if the next cycle exists, the flow goes back to Step  304 ; otherwise, the flow enters Step  314 . 
     The above-mentioned Steps  302 - 312  are used to determine how many cycles in the frame data are influenced by noise, and the parameter n is a number of cycles influenced by the noise. Taking the frame data shown in  FIG. 2  as an example and assuming that A is equal to 3 and B is equal to 10, only cycle  7  and cycle  8  are determined to be influenced by the noise (minimum value is greater than 3 and the difference is less than 10), and the parameter n is equal to “2”. 
     In Step  314 , it is determined whether the parameter n is greater than a threshold value C or not (in this embodiment, C can be 2). If the parameter n is greater than a threshold value C, the flow enters Step  318  and the value of a parameter m is increased by an increment of 1 (initially, the parameter m is set to be “0”); otherwise, the flow enters Step  316  to set the parameter m to be “0”. In Step  320 , it is determined whether the parameter m is greater than a threshold value D or not (in this embodiment, D can be 1 or 2): if the parameter m is greater than D, the flow enters Step  322  to slightly change a frequency of the transmitting signals T 1 -T 19  (without influencing the normal operations of the touch panel  100 ); otherwise, the flow enters Step  324 . In Step  324 , it is determined whether a next frame exists: if the next frame exists, the flow goes back to Step  302 ; otherwise, the flow enters Step  326  to finish the operations. 
     The above-mentioned Steps  314 - 324  are used to determine whether the current frame is influenced by noise, and to determine how many continuous frames are influenced by noise, and the parameter m is used to represent a number of continuous frames influenced by noise. Assuming that C is equal to 2, the frame is determined to be influenced by noise only when a number of cycles influenced by noise (i.e. the parameter n) is greater than 2. Taking  FIG. 2  as an example, because only two cycles are determined to be influenced by noise, the frame shown in  FIG. 2  is determined to not be influenced by noise. In addition, assuming that D is equal to 1, when two or more frames are determined to be influenced by noise, the controller  110  will slightly change a frequency of the transmitting signals T 1 -T 19 ; otherwise, the frequency of the transmitting signals T 1 -T 19  is not changed. 
     The flow shown in  FIG. 3  is executed during the whole operation period of the touch panel  100 . The controller  110  detects the noise of the touch panel  100  and performs signal control in a real-time manner. 
     To discuss the flow shown in  FIG. 3 , the method shown in  FIG. 3  uses four conditions to check/detect whether or not to change the frequency of the transmitting signals T 1 -T 19  for lowering the noise: 
     Condition 1: at one cycle, the minimum value is greater than A; 
     Condition 2: at one cycle, the difference value between the maximum value and the minimum value is less than B; 
     Condition 3: at one frame, n cycles satisfy Condition 1 and Condition 2, where n is greater than C. 
     Condition 4: m continuous frames satisfy Condition 3, where m is greater than D. 
     If Condition 4 is satisfied, the controller  110  slightly changes the frequency of the transmitting signals T 1 -T 19  to lower the noise of the touch panel. 
     The Steps  306  and  308  and the above-mentioned Condition 1 and Condition 2 are for illustrative purposes only. In other embodiments, other methods or criteria can also be used to determine whether the cycle is influenced by noise. 
     Briefly summarized, in the method for detecting touch panel noise and performing signal control, noise can be accurately detected by using a simple algorithm, and the noise can be lowered by simply changing the frequency of the transmitting signals. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.