Abstract:
A capacitive touch system uses two or more integrated circuits to simultaneously scan a touch panel in such a manner that each of the integrated circuits scans only a portion of the touch panel to retrieve a respective detected data by itself. All the detected data are used for computation by one of the integrated circuits or one other than the integrated circuits to determine a touch information. This approach enables axis intersect projected capacitance touch integrated circuits applicable to a large scale touch panel, without degrading the frame rate of a capacitive touch system.

Description:
FIELD OF THE INVENTION 
     The present invention is related generally to a capacitive touch system and, more particularly, to a capacitive touch system using two or more integrated circuits (ICs) to scan a touch panel. 
     BACKGROUND OF THE INVENTION 
     In conventional applications, all the large scale capacitive touch panels use a surface capacitance sensing technique to scan thereto for determining a touch information, which uses a set of detecting currents, each directed to an endpoint of the large scale touch panel to produce detected values, and therefore, even multiple fingers simultaneously touch the large scale touch panel, this sensing technique still retrieves only one set of detected currents in response to this multi-finger touch. For this reason, the surface capacitance sensing technique can identify only one set of absolute coordinates. In a two dimensional matrix for instance, only one set of parameters (X,Y) will be determined, and thereby it can&#39;t implement a multi-finger touch detection. 
     An all points addressable (APA) projected capacitance sensing technique is capable of implementing a multi-finger touch detection, but not applicable to large scale touch panels because, to implement this sensing technique, it is necessary to charge and discharge each point sensor on the large scale touch panel. Taking a matrix-type touch panel for example, when the X and Y traces increase, the pixel number of an APA projected capacitance touch panel dramatically increases and thereby significantly degrades the frame rate of the touch panel due to the very long time period for scanning the large scale touch panel in a frame. 
     An axis intersect (AI) projected capacitance sensing technique is also capable of implementing a multi-finger touch detection, but not applicable to large scale touch panels, too.  FIG. 1  is a schematic diagram of a conventional AI projected capacitance sensing technique applied to a small scale touch panel  10 , in which an AI projected capacitance touch IC  12  is used to scan the small scale touch panel  10 . Assuming that the AI projected capacitance touch IC  12  can support up to 22 traces, a good frame rate can be attained for a small scale touch panel  10  having ten X traces TRX 1 -TRX 10  and ten Y traces TRY 1 -TRY 10 . However, if a this type touch IC  12  is applied to a large scale touch panel  14  having forty X traces TRX 1 -TRX 40  and forty Y traces TRY 1 -TRY 40 , as shown in  FIG. 2 , the total number of traces that the touch IC  12  needs to scan dramatically increases. Unfortunately, the frame rate of the overall touch panel application is dependent to a very large extent on the time it takes the touch IC  12  to charge and discharge capacitors each time. In other words, the frame rate is determined mainly by the time in a frame that the touch IC  12  charges and discharges the capacitors. Hence, if an AI projected capacitance touch IC capable of scanning a greater number of traces is applied to a large scale touch panel  14 , a major drawback would be a significantly decreased frame rate in the overall application, which leads to compromised performance at the application end. 
     Therefore, it is desired a sensing method applicable to large scale touch panels, capable of implementing a multi-finger touch detection thereto, and maintaining a good frame rate thereof. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a capacitive touch system using two or more touch ICs to scan a touch panel and a control method for this capacitive touch system. 
     Another object of the present invention is to provide a capacitive touch system applicable to large scale touch panels, capable of implementing a multi-finger touch detection thereto, and maintaining a good frame rate thereof, and a control method for this capacitive touch system. 
     According to the present invention, a capacitive touch system includes a touch panel and two or more integrated circuits connected to the touch panel. Each of the integrated circuits scans only a portion of the touch panel to retrieve a respective detected data by itself, and then all the detected data are used for computation by one of the integrated circuits or one other than the integrated circuits, to determine a touch information. Since two or more integrated circuits simultaneously scan a touch panel for determining a touch information, a capacitive touch system can maintain a good frame rate, even for a large scale touch panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram of a conventional AI projected capacitance sensing technique applied to a small scale touch panel; 
         FIG. 2  is a schematic diagram of a conventional AI projected capacitance sensing technique applied to a large scale touch panel; 
         FIG. 3  is a schematic diagram of a first embodiment according to the present invention; 
         FIG. 4  is a schematic diagram of a second embodiment according to the present invention; 
         FIG. 5  is a schematic diagram of a third embodiment according to the present invention; 
         FIG. 6  is a schematic diagram of a fourth embodiment according to the present invention; 
         FIG. 7  is a schematic diagram of a fifth embodiment according to the present invention; 
         FIG. 8  is a schematic diagram of a sixth embodiment according to the present invention; and 
         FIG. 9  is a schematic diagram of a seventh embodiment according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In a first embodiment according to the present invention, as shown in  FIG. 3 , a capacitive touch system  20  includes a large scale touch panel  22  and, to scan the large scale touch panel  22 , two AI projected capacitance touch ICs  24  and  26  connected to the large scale touch panel  22  by m traces TR 1 -TRm, where m is a natural number. For the scan operation in a frame, the slave touch IC  24  scans from the trace TR 1  to the trace TRn, and the master touch IC  26  scans from the trace TRn or TRn+1 to the trace TRm, where 1&lt;n&lt;m. Since each of the touch ICs  24  and  26  only scans a portion of the large scale touch panel  22 , they can simultaneously scan their responsible traces in a frame. It is understood that the scanning sequence may be reversed so that the slave touch IC  24  scans from the trace TRn to the trace TR 1 , and the master touch IC  26  scans from the trace TRm to the trace TRn or TRn+1. The overall detected data of a touch on the large scale touch panel  22  is thus separated, retrieved by the touch ICs  24  and  26  respectively. In further detail, the slave touch IC  24  retrieves a first detected data by scanning the traces TR 1 -TRn, and the master touch IC  24  retrieves a second detected data by scanning the traces TRn-TRm or TRn+1-TRm. The touch ICs  24  and  26  are also connected to each other, and the master touch IC  26  sends a clock CLK to the slave touch IC  24  in order to collect the first detected data therefrom in a synchronous manner. Each time, after scanning, the slave touch IC  24  transmits its first detected data SDA to the master touch IC  26 , where the first and second detected data are used for computation to determine a touch information which may include one or more touch positions on the large scale touch panel  22 . In addition, the master touch IC  26  is also configured to coordinate the overall operation of the capacitive touch system  20  and responsible for external communications. In one embodiment, the slave touch IC  24  may be responsible for some computation to reduce the load of the master touch IC  26 . For instance, the slave touch IC  24  may calculate with the detected values that it obtains from the scanning to the large scale touch panel  22  to produce the detected data SDA. Since the touch ICs  24  and  26  simultaneously scan their respective portions of the traces TR 1 -TRm in a frame, assuming m=40 and n=20, the forty traces of the large scale touch panel  22  is completely scanned once, only with the time it takes to scan twenty traces, thereby effectively improving the frame rate of the capacitive touch system  20 . 
     For more larger scale touch panel,  FIG. 4  is a schematic diagram of a second embodiment according to the present invention, in which a capacitive touch system  30  uses three AI projected capacitance touch ICs  34 ,  36  and  38 , one mater and two slave, to scan a large scale touch panel  32  by m traces TR 1 -TRm, where m is a natural number. For a frame, the slave touch IC  34  scans from the trace TR 1  to the trace TRk, the slave touch IC  36  scans from the trace TRk or TRk+1 to the trace TRn, and the master touch IC  38  scans from the trace TRn or TRn+1 to the trace TRm, where 1&lt;k&lt;n&lt;m. The slave touch ICs  34  and  36  are parallel connected to the master touch IC  38  that sends a clock CLK to each of the slave touch ICs  34  and  36  and selects therebetween with an address signal AD to request for detected data therefrom. Each time, after scanning, the slave touch ICs  34  and  36  transmit their respective detected data SDA to the master touch IC  38  where to execute final computation with the detected data SDA received from the slave touch ICs  34  and  36  and the detected data obtained by the master touch IC  38  scanning the large scale touch panel  32 , determine a touch information which may include one or more touch positions on the large scale touch panel  32 . Additionally, the master touch IC  38  is also configured to coordinate the overall operation of the capacitive touch system  30  and responsible for external communications. In addition to scan the large scale touch panel  32 , each of the slave touch ICs  34  and  36  may also be responsible for some computation to reduce the load of the master touch IC  38 , e.g. calculation with its detected values to produce its detected data SDA. Since the touch ICs  34 ,  36  and  38  simultaneously scan their respective portions of the traces TR 1 -TRm in a frame, the frame rate of the capacitive touch system  30  can be effectively improved, only about a third times of that by using only one touch IC to scan the large scale touch panel  32 . 
     Alternatively,  FIG. 5  is a schematic diagram of a third embodiment according to the present invention, in which a capacitive touch system  40  includes two slave touch ICs  44  and  46  to scan a large scale touch panel  42  by traces TR 1 -TRm, and a master touch IC  48  for computation with the detected data retrieved by the slave touch ICs  44  and  46  to determine a touch information. In this embodiment, all the touch ICs  44 ,  46  and  48  are AI projected capacitance touch ICs, but the master touch IC  48  does not directly scan the large scale touch panel  42 . In a frame, the slave touch IC  44  scans from the trace TR 1  to the trace TRn and the slave touch IC  46  scans from the trace TRn or TRn+1 to the trace TRm. Although the master touch IC  48  does not participate in scanning, it is still configured to receive the detected data from the slave touch ICs  44  and  46 , carry on the final computation with all the detected data to determine a touch information, coordinate the overall operation of the capacitive touch system  40 , and be responsible for external communications. For request of detected data, the master touch IC  48  sends a clock CLK to the slave touch ICs  44  and  46  and selects therebetween with an address signal AD. Each time, after scanning, the slave touch ICs  44  and  46  transmit their detected data SDA to the master touch IC  48  where final computation with the detected data SDA is executed and one or more touch positions on the touch panel  42  could be identified. In addition to scan the large scale touch panel  42 , each of the slave touch ICs  44  and  46  may also execute some computation to reduce the load of the master touch IC, e.g. calculation with its detected values to produce its detected data SDA. Since the slave touch ICs  44  and  46  simultaneously scan their respective portions of the traces TR 1 -TRm in a frame, the frame rate of the capacitive touch system  40  can be effectively improved, only about a half of that by using only one touch IC to scan the large scale touch panel  42 . Since the master touch IC  48  does not directly scan the large scale touch panel  42 , in other embodiments, it may use another type IC instead of the AI projected capacitance touch IC. 
       FIG. 6  is a schematic diagram of a fourth embodiment according to the present invention, in which a capacitive touch system  50  includes a large scale touch panel  52  and five touch ICs  54 ,  56 ,  58 ,  60  and  62 . All the slave touch ICs  54 - 60  are AI projected capacitance touch ICs, while the master touch IC  62  is either an AI projected capacitance touch IC or an another type IC. In this embodiment, the scanning to the X traces and the Y traces is split, two of the slave touch ICs, i.e.  54  and  56 , are arranged on the left side of the large scale touch panel  52 , and the other two  58  and  60  are arranged on the bottom side of the large scale touch panel  52 . The large scale touch panel  52  has forty X traces TRX 1 -TRX 40  and forty Y traces TRY 1 -TRY 40 . The slave touch IC  54  is located above the slave touch IC  56  and the slave touch IC  58  is located on the left side of the slave touch IC  60 . For the scanning in a frame, the slave touch IC  58  scans from the trace TRX 1  to the trace TRX 20 , the slave touch IC  60  scans from the trace TRX 20  or TRX 21  to the trace TRX 40 , the slave touch IC  56  scans from the trace TRY 1  to the trace TRY 20 , and the slave touch IC  54  scans from the trace TRY 20  or TRY 21  to the trace TRY 40 . The master touch IC  62  does not participate in scanning but is configured to receive all the detected data retrieved by the slave touch ICs  54 - 60 , calculate with all the detected data to determine a touch information, coordinate the overall operation of the capacitive touch system  50 , and be responsible for external communications. For request of the detected data, the master touch IC  62  sends a clock CLK to the slave touch ICs  54 - 60  and selects therebetween with an address signal AD. Each time, after scanning, the slave touch ICs  54 - 60  transmit their detected data SDA to the master touch IC  62  where final computation is executed with all the detected data SDA and one or more touch positions on the large scale touch panel  52  could be identified. In addition to scan the large scale touch panel  52 , each of the slave touch ICs  54 - 60  may also be responsible for some computation to reduce the load of the master touch IC  62 , e.g. calculation with its detected values to produce its detected data SDA. Since the four slave touch ICs  54 - 60  simultaneously scan their respective portions of the traces TRX 1 -TRX 40  and TRY 1 -TRY 40  in a frame, the frame rate of the capacitive touch system  50  can be effectively improved, only about a fourth times of that by using only one touch IC to scan the large scale touch panel  52 . 
     Alternatively,  FIG. 7  is a schematic diagram of a fifth embodiment according to the present invention, in which four slave touch ICs  74 ,  76 ,  78  and  80  are used to scan a large scale touch panel  72  having forty X traces TRX 1 -TRX 40  and forty traces TRY 1 -TRY 40 . Each of the slave touch ICs  74 - 80  is an AI projected capacitance touch IC, and is responsible for scanning a portion of the X traces TRX 1 -TRX 40  and a portion of the Y traces TRY 1 -TRY 40  to retrieve a respective detected data. The slave touch ICs  74  and  76  are arranged on the upper right corner of the large scale touch panel  72 , and the slave touch ICs  78  and  80  are arranged on the lower left corner of the touch panel  72 . In further detail, the slave touch IC  74  is located on the upper right corner of the slave touch IC  76 , and the slave touch IC  78  is located on the upper right corner of the slave touch IC  80 . The slave touch IC  78  scans the traces TRX 1 -TRX 10  and TRY 1 -TRY 10 , the slave touch IC  80  scans the traces TRX 11 -TRX 20  and TRY 11 -TRY 20 , the slave touch IC  74  scans the traces TRX 21 -TRX 30  and TRY 21 -TRY 30 , and the slave touch IC  76  scans the traces TRX 31 -TRX 40  and TRY 31 -TRY 40 . A master touch IC  82  does not participate in scanning but is configured to receive all the detected data from the slave touch ICs  74 - 80 , calculate with all the detected data to determine a touch information, coordinate the overall operation of the capacitive touch system  70 , and be responsible for external communications. For request of the detected data, the master touch IC  82  sends a clock CLK to the slave touch ICs  74 - 80  and selects therebetween with an address signal AD. Each time, after scanning, the slave touch ICs  74 - 80  transmit their detected data SDA to the master touch IC  82  where final computation is executed with all the detected data SDA and one or more touch positions on the large scale touch panel  72  could be identified. In addition to scan the large scale touch panel  72 , each of the slave touch ICs  74 - 80  may also be responsible for some computation to reduce the load of the master touch IC  82 , e.g. calculation with its detected values to produce its detected data SDA. Since the four slave touch ICs  74 - 80  simultaneously scan their respective portions of the traces TRX 1 -TRX 40  and TRY 1 -TRY 40  in a frame, the frame rate of the capacitive touch system  70  can be effectively improved, only about a fourth times of that by using only one touch IC to scan the large scale touch panel  72 . The master touch IC  82  is either an AI projected capacitance touch IC or an another type IC. 
     Alternatively,  FIG. 8  is a schematic diagram of a sixth embodiment according to the present invention, in which a capacitive touch system  90  includes a large scale touch panel  92  having forty X traces TRX 1 -TRX 40  and forty Y traces TRY  1 -TRY 40 , and five touch ICs  94 ,  96 ,  98 ,  100  and  102  arranged on the lower left corner of the large scale touch panel  92  in such a manner that the slave touch IC  94  is on the upper right corner of the slave touch IC  96 , the slave touch IC  96  is on the upper right corner of the slave touch IC  98 , the slave touch IC  98  is on the upper right corner of the slave touch IC  100 , and the slave touch IC  100  is on the upper right corner of the master touch IC  102 . Each of the slave touch ICs  94 - 100  is an AI projected capacitance touch IC, and the master touch IC is either an AI projected capacitance touch IC or an another type IC. The slave touch IC  94  scans the traces TRX 1 -TRX 10  and TRY 1 -TRY 10 , the slave touch IC  96  scans the traces TRX 11 -TRX 20  and TRY 11 -TRY 20 , the slave touch IC  98  scans the traces TRX 21 -TRX 30  and TRY 21 -TRY 30 , and the slave touch IC  100  scans the traces TRX 31 -TRX 40  and TRY 31 -TRY 40 . Each of the slave touch ICs  94 - 100  retrieves a respective detected data by itself, and sends it to the master touch IC  102 . The master touch IC  102  does not participate in scanning but is configured to receive all the detected data from the slave touch ICs  94 - 100 , calculate with all the detected data to determine a touch information, coordinate the overall operation of the capacitive touch system  90 , and be responsible for external communications. For request of the detected data, the master touch IC  102  sends a clock CLK to the slave touch ICs  94 - 100  and selects therebetween with an address signal AD. Each time, after scanning, the slave touch ICs  94 - 100  transmit their detected data SDA to the master touch IC  102  where final computation is executed with all the detected data SDA and one or more touch positions on the large scale touch panel  92  could be identified. In addition to scan the large scale touch panel  92 , each of the slave touch ICs  94 - 100  may also be responsible for some computation to reduce the load of the master touch IC  102 , e.g. calculation with its detected values to produce its detected data SDA. Since the four slave touch ICs  94 - 100  simultaneously scan their respective portions of the traces TRX 1 -TRX 40  and TRY 1 -TRY 40  in a frame, the frame rate of the capacitive touch system  90  can be effectively improved, only about a fourth times of that by using only one touch IC to scan the large scale touch panel  92 . The master touch IC  102  is either an AI projected capacitance touch IC or an another type IC. 
       FIG. 9  is a schematic diagram of a seventh embodiment according to the present invention, in which a capacitive touch system  110  includes a large scale touch panel  112  and five touch ICs  114 ,  116 ,  118 ,  120  and  122 . The slave touch ICs  114  and  116  are arranged on the lower left corner of the large scale touch panel  112 , and the slave touch ICs  118  and  120  are on the lower right corner of the large scale touch panel  112 . In further detail, the slave touch IC  114  is on the lower left corner of the slave touch IC  116 , and the slave touch IC  118  is on the upper left corner of the slave touch IC  120 . The large scale touch panel  112  has forty X traces TRX 1 -TRX 40  and forty Y traces TRY 1 -TRY 40 . The slave touch IC  116  scans the traces TRX 1 -TRX 10  and TRY 1 -TRY 10 , the slave touch IC  114  scans the traces TRX 11 -TRX 20  and TRY 11 -TRY 20 , the slave touch IC  120  scans the traces TRX 21 -TRX 30  and TRY 31 -TRY 40 , and the slave touch IC  118  scans the traces TRX 31 - 7 TRX 40  and TRY 21 -TRY 30 . Each of the slave touch ICs  116 - 120  is an AI projected capacitance touch IC and retrieves a respective detected data to send to the master touch IC  122 . The master touch IC  122  does not participate in scanning but is configured to receive all the detected data from the slave touch ICs  114 - 120 , calculate with all the detected data to determine a touch information, coordinate the overall operation of the capacitive touch system  110 , and be responsible for external communications. For request of the detected data, the master touch IC  122  sends a clock CLK to the slave touch ICs  114 - 120  and selects therebetween with an address signal AD. Each time, after scanning, the slave touch ICs  114 - 120  transmit their detected data SDA to the master touch IC  122  where final computation is executed with all the detected data SDA and one or more touch positions on the large scale touch panel  112  could be identified. In addition to scan the large scale touch panel  112 , each of the slave touch ICs  114 - 120  may also be responsible for some computation to reduce-the load of the master touch IC  122 , e.g. calculation with its detected values to produce its detected data SDA. Since the slave touch ICs  114 - 120  simultaneously scan their respective portions of the traces TRX 1 -TRX 40  and TRY 1 -TRY 40  in a frame, the frame rate of the capacitive touch system  110  can be effectively improved, only about a fourth times of that by using only one touch IC to scan the large scale touch panel  112 . The master touch IC  122  is either an AI projected capacitance touch IC or an another type IC. 
       FIGS. 6-9  demonstrate four configurations of a capacitive touch system according to the present invention. As the locations of the slave touch ICs vary, the wire length between the traces and the slave touch ICs also vary, which may influence the performance of a capacitive touch system. Furthermore, in  FIGS. 5-9 , the master touch ICs  48 ,  62 ,  82 ,  102  and  112 , which are not responsible for scanning the touch panels, are not necessarily implemented by capacitive touch ICs and may be replaced by general ICs. Moreover, in  FIGS. 3-9 , the AI projected capacitance touch ICs may also be replaced by other projected capacitance touch ICs, such as the APA projected capacitance touch ICs. 
     While the present invention has been described in conjunction with preferred embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope thereof as set forth in the appended claims.