Patent Publication Number: US-8115747-B2

Title: Energy-efficient touch panel device and related method

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to an energy-efficient touch panel device and related method, and more particularly, to a touch panel device and related method which can consume less power and have a long standby time. 
     2. Description of the Prior Art 
     For years, most IT products utilized traditional ways like keyboards or mouse as the standard user interfaces. After the touch panel devices emerged as a new type of user interface, people start to enjoy it as a very convenient way to input command by selecting objects on the screen. On the other hand, as the concept of environmental protection draws more and more attention, and as new generations of IT products appear on the market, the concepts of “green product” gradually influence all design and manufacturing works of the IT products, which include the touch panel device. Besides that, saving power consumption can have other benefits, too; for example, the standby time of the IT product can be extended, and the users need not to charge the battery of the device very often, so the users&#39; convenience can be advanced. 
     The touch panel and related control device are mostly seen in the portable IT products. Please refer to  FIG. 1 .  FIG. 1  illustrates a schematic diagram of a touch panel PANEL 1  and a control device  12  according to the prior art. The touch panel PANEL 1  usually includes many traces in the horizontal direction (X trace) and vertical direction (Y trace), for forming the touch panel functions on the touch panel; these traces are used for sensing the human body∝s capacitance in order to generate analog output voltages. Meanwhile, according to the operating principles of the touch panel, different traces correspond to different capacitive load parameters. 
     When a touch event happens to the touch panel PANEL 1 , the analog output voltages of some horizontal traces as well as some vertical traces may change according to where the touch event happened, and the control device  12  can detect the touch event by monitoring the analog output voltage of each trace. Inside  FIG. 1 , connected to the touch panel PANEL 1 , there is a control device  12 , which includes an analog to digital converter  120 , an operating control unit  122  and a host interface unit  124 . The analog to digital converter  120 , directly connected to the touch panel PANEL  1 , is used for converting the analog output voltages into some data in digital format, and the resulting digital data is then transferred to the operating control unit  122 . The operating control unit  122  performs specific algorithms to process the data to judge whether there exists a touch event. When the operating control unit  122  confirms a touch event, the host interface unit  124  will output a message to a computer host HOST 1  to notify the happening of the touch event. Noticeably, since different traces in the touch panel have different capacitive load parameters, every time the analog to digital converter  120  converts an analog output voltage, the analog to digital converter  120  needs to regulate its transfer ratio (magnitude of amplification) based on the capacitive load parameter of the corresponding trace, such that the influence of different capacitive load corresponding to different trace can be erased (normalized). By this way, the digital data output by the analog to digital converter  120  can be normalized by the analog to digital converter  120 , and the operating control unit  122  can perform data operations based on those normalized data. 
     Noteworthily, inside the control device  12 , between the operating control unit  122  and the analog to digital converter  120 , the capacitive load parameters, used for regulating the transfer ratio of the analog to digital converter, are supplied by the operating control unit  122  one at a time. In other words, every time the analog to digital converter  120  performs a conversion, only one corresponding capacitive load parameter is transferred from the operating control unit  122  to “update” the transfer ratio of the analog to digital converter  120 . Meanwhile, right after each analog to digital conversion, the digital output is directly transferred to the operating control unit  122 . Therefore, based on the operating principles described above, the control device  12  has been busy on sending capacitive load parameters to and receiving data from the analog to digital converter  120 , and could consume electric power unnecessarily, such that the standby time of the touch panel device cannot be reasonably extended, and user&#39;s convenience cannot be improved, either. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary objective of the claimed invention to provide an energy-efficient touch panel device and related method. 
     The present invention discloses an energy-efficient touch panel control device, which comprises a touch panel comprising a plurality of horizontal traces and a plurality of vertical traces, corresponding to a plurality of capacitive load parameters, for generating a plurality of analog output voltages; a buffer memory for storing data; an interrupt initiation unit, for counting a data number of the data stored in the buffer memory, and outputting an interrupt signal while the data number is greater than or equal to a predefined value; an analog to digital conversion unit, coupled to the touch panel and the buffer memory, for converting the plurality of analog output voltages to a plurality of digital trace data and storing the plurality of digital trace data in the buffer memory, and switching an operating mode according to a control signal; an operation unit, coupled to the buffer memory, for generating a detecting result according to the plurality of digital trace data, and switching the operating mode according to the control signal; a mode control unit, coupled to the interrupt initiation unit, the operation unit and the analog to digital conversion unit, for generating the first control signal to the analog to digital conversion unit, and the second control signal to the operation unit according to the interrupt signal; and a host interface unit, coupled to the operation unit, for transmitting a touch event message to a computer host according to the detecting result. 
     The present invention further discloses an energy-efficient touch panel control method, which comprises utilizing an analog to digital conversion unit to transform a plurality of analog output voltages into a plurality of digital trace data according to a plurality of capacitive load parameters; storing the plurality of the digital trace data into a buffer memory; and controlling operating modes of the analog to digital conversion unit and an operation unit according to a data number of the data stored in the buffer memory. 
     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  illustrates a schematic diagram of a touch panel and a control device according to the prior art. 
         FIG. 2  illustrates a schematic diagram of a touch panel control device according to the present invention. 
         FIG. 3  is a schematic diagram of a process of an embodiment of the present invention applies to the touch panel control device. 
         FIGS. 4A and 4B  illustrate simplified timing diagrams while varying the memory size of the buffer memory. 
     
    
    
     DETAILED DESCRIPTION 
     Please refer to  FIG. 2 , which illustrates a schematic diagram of a touch panel control device  20  according to the present invention. The touch panel control device  20 , connected to a touch panel PANEL 2 , is used for detecting the presence of a touch event and sending the detection result to a computer host HOST 2 . The touch panel control device  20  comprises a buffer memory  202 , an interrupt initiation unit  204 , an analog to digital conversion unit  206 , an operation unit  208 , a mode control unit  210  and a host interface unit  212 . 
     a. The operations of the touch panel control device  20  are described as follows. First, the mode control unit  210  sets the analog to digital conversion unit  206  to work in an active mode, and sets the operation unit  208  to stay in a sleep mode. The analog to digital conversion unit  206  converts the analog output voltages to digital trace data by referring the traces&#39; capacitive load parameters, and stored in the buffer memory  202 . The buffer memory  202  supplies a memory space for temporarily storing the digital trace data, and the interrupt initiation unit  204  is responsible for counting the number of digital trace data stored in the buffer memory  202 . Besides, when the number of digital trace data stored in the buffer memory  202  is equal to or greater than a preset value MLEVEL, the interrupt initiation unit  204  will submit an interrupt signal INTM, and the mode control unit  210  will generate control signals, SWM 1  and SWM 2  according to the interrupt signal INTM. The analog to digital conversion unit  206  will switch its operating mode according to the control signal SWM 1 , and the operation unit  208  will switch its operating mode according to the control signal SWM 2 . Preferably, for the present case, the control signal SWM 1  switches the analog to digital conversion unit  206  to a sleep mode, and the control signal SWM 2  switches the operation unit  208  to an active mode, such that the electric power can be saved by turning the analog to digital conversion unit  206  into an idle condition. Besides, preferably, the preset value MLEVEL, used for setting a limit on the number of digital trace data in the buffer memory  202 , is less than or equal to the data capacity of the buffer memory  202 . 
     On the other hand, the operation unit  208  reads the digital trace data in the buffer memory  202 , performs algorithmic operations, and generates a detection result. When the operation unit  208  completes the algorithmic operation and generates a detection result, all the data stored in the buffer memory  202  should have been consumed (read) by the operation unit  208 , the mode control unit  210  can then switch the operation mode of the switch touch panel control device  20  via the control signals, SWM 1  and SWM 2 . Preferably, for the present condition, the control signal SWM 1  switches the analog to digital conversion unit  206  back to work in an active mode, and the control signal SWM 2  switches the operation unit  208  into a sleep mode; by following this procedure, the electric energy can be saved by turning the operation unit  208  into an idle state. 
     As stated above, the mode control unit  210  is used for generating the control signals, SWM 1  and SWM 2 , which are used for controlling the operation modes of the analog to digital conversion unit  206  and the operation mode  208 , respectively, such that the electric energy can be saved. Noticeably and preferably, the control signals, SWM 1  and SWM 2 , can be implemented as a single control signal, or can be two different control signals. On the other hand, the host interface unit  212  is in charge of transferring a touch event message to the computer host HOST 2 . Besides that, the touch panel control device  20  includes a non-volatile program memory  220 , which is connected to the operation unit  208 , and is used for storing the software code used for the operations of the operation unit  208  as well as the capacitive load parameters of all the traces. Meanwhile, the touch panel control device  20  includes a load parameter storing unit  222  directly connected to the analog to digital conversion unit  206 . Preferably, every time when the system is reset or bootstrapped, the operation unit  208  is responsible for transferring every capacitive load parameters stored in the program memory  220  and storing them in the load parameter storing unit  222 . After that, the analog to digital conversion unit  206  can access any of the capacitive load parameters directly from the load parameter storing unit  222 . Besides, preferably, the buffer memory  202  and the load parameter storing unit  222  can be implemented as one single memory module, or as two separate memory modules. 
     Noticeably, the touch panel control device  20  uses the buffer memory  202  to store a large number of data; firstly, by temporarily storing the digital trace data generated by the analog to digital conversion unit  206  to the buffer memory  202 , so that the analog to digital conversion unit  206  is not required to output the digital trace data directly to the operation unit  208  every time an analog-to-digital conversion completes. Besides, every time the touch panel control device  20  is bootstrapped or reset, the operation unit  208  coordinates the transfer of capacitive load parameters from the program memory  220  to the load parameter storing unit  222 . Therefore, every time the touch panel control device  20  performs an analog to digital conversion, the analog to digital conversion unit  206  will not require the operation unit  208  to send a corresponding capacitive load parameter; instead, the analog to digital conversion unit  206  can access the corresponding capacitive load parameter directly from the load parameter storing unit  222 . Therefore, compared with the prior art, the analog to digital conversion unit  206  can operate independently and complete the analog to digital conversion without the assistance of the operation unit  208 . 
     Most importantly, the touch panel control device  20  can coordinate the analog to digital conversion unit  206  and the operation unit  208  to be operated in an active mode or a sleep mode, such that part of the electric power can be saved. In other words, when the number of digital trace data stored in the buffer memory  202  is equal to or greater than the preset value MLEVEL, the interrupt initiation unit  20  generates an interrupt signal INTM, and then the mode control unit  210  can generate control signals, SWM 1  and SWM 2 , based on the interrupt signal INTM, such that the analog to digital conversion unit  206  enters into a sleep mode, and the operation unit  208  is being “waken up” and enters into an active mode. After the operation unit  208  reads the digital trace data stored in the buffer memory  202 , and completes the algorithmic operations about the detection of touch event, the mode control unit  210  wakes up the analog to digital conversion unit  206 , and makes it enter into an active mode, and makes the operation unit  208  enter into a sleep mode. By following this process, the analog to digital conversion unit  206  and the operation unit  208  can be put into sleep mode alternatively, so part of the electric power can be saved. 
     To detail more about the operations of the touch panel control device  20 , please refer to  FIG. 3 , which is a schematic diagram of a process  30  of an embodiment of the present invention applies to the touch panel control device  20 . It would have been obvious to one of ordinary skill in the art to understand that process  30  is for explaining the methods and the benefits disclosed in the present invention, and is including but not limited just to this. The process  30  comprises the following steps: 
     STEP  300 : Start. 
     STEP  302 : The capacitive load parameters stored in the program memory  220  are being transferred to the load parameter storing unit  222 . 
     STEP  304 : Set the value MLEVEL according to the memory size of the buffer memory  202  and the applications. 
     STEP  306 : Introduce the analog to digital conversion unit  206  into an active mode according to the control signal SWM 1 . 
     STEP  308 : Introduce the operation unit  208  into a sleep mode according to the control signal SWM 2 . 
     STEP  310 : The analog to digital conversion unit  206  converts the analog output voltage into digital trace data according to the capacitive load parameter, and stores the digital trace data in the buffer memory  202 . 
     STEP  312 : Judge whether the number of digital trace data stored in the buffer memory  202  is greater than or equal to the preset value MLEVEL; if not, go back to STEP  310 . 
     STEP  314 : The interrupt initiation unit  204  generates an interrupt signal INTM. 
     STEP  316 : The mode control unit  210  generates the control signal SWM 2 , wakes up the operation unit  208 , and enters into the active mode according to the interrupt signal INTM. 
     STEP  318 : The operation unit  208  completes reading the digital trace data stored in the buffer memory  202 , the mode control unit  210  generates the control signal SWM 1 , and introduces the analog to digital conversion unit  206  into a sleep mode. 
     STEP  320 : The operation unit  208  performs algorithmic operations to detect the happening of a touch event according to the received digital trace data. 
     STEP  322 : Judge whether a touch event happens; if not, go back to STEP  306 . 
     STEP  324 : The host interface unit  212  transfers the detection result about the touch event in a format of data packet to the computer host HOST 2 , and go back to STEP  306 . 
     According to process  30 , preferably, the STEP  310 ,  312  and  314  are performed by the analog to digital conversion unit  206  and the interrupt initiation unit  204 , and the rest of the STEPs are performed by the operation unit  208  and the mode control unit  210 . The related hardware units described in the process  30 , and their placements, connection relations and corresponding functions have been disclosed as above, and will not be detailed further. 
     Besides, preferably, the present invention can save more power by increasing the memory size of the buffer memory  202 . Please refer to  FIGS. 4A and 4B , which illustrate the simplified timing diagrams while varying the memory size of the buffer memory  202 . The analog to digital conversion unit  206  and the operation unit  208  alternatively operated in a sleep mode (denoted by  0 ) or in an active mode (denoted by  1 ).  FIGS. 4A and 4B  illustrate the operating states of the analog to digital conversion unit  206  and the operation unit  208  when the size of the buffer memory is L 1  and L 2  bytes, respectively. By comparing  FIGS. 4A and 4B , it can be observed that, when the data capacity of the buffer memory  20  expands, the operation unit  208  will stay longer in the sleep mode, since it will take more time to fill up the buffer memory  202 . In other words, if the memory size L 2  is greater than the memory size L 1 , the time interval T 3  will be greater than the time interval T 1 . Besides, since the time interval T 2  is approximately equal to the time interval T 4 , expanding the memory size of the buffer memory  202  can make the operation unit  208  stays in the sleep mode at a greater proportion of time, and then more electric power can be saved. Noticeably, when the time difference between two “wake-ups” of the operation unit  208  has been lengthened, some users may sense the response time of the touch panel control device  20  increased, or the sensitivity decreased. Therefore, the designer is required to find an optimal value for the memory size of the buffer memory  202  by considering the system cost and the sensitivity of the touch panel control device  20 . 
     Noticeably, the present invention can apply a simple hardware module (not shown in the figures), which is specifically used for monitoring the data converted by the analog to digital conversion unit  206 , such that the converted data can be checked first to see whether any meaningful message is immersed in the data. Next, only the data with meaningful message and its associated trace position information are transferred to the buffer memory  202 . In this case, the operation unit  208  can spend more time to stay in the sleep mode, and the power consumption can be lowered further by adding this hardware function. After all, the operation unit  208  can be waken up and come back in the active mode, and can process only the data with meaningful messages. 
     According to the experimental results, for the control device  12  of the prior art, the analog to digital converter  120  and the operating control unit  122  are the two most power consuming modules; between them, the operating control unit  122  consumes even more. This is understandable because the operating control module  120  needs to perform the data processing tasks, and to supply the analog to digital converter  120  with characteristic data (capacitive load parameter) of the corresponding trace, and then to receive the digital data output by the analog to digital converter  120  after every analog to digital conversion; all these have to be done in real time, and therefore consume more power. In the prior art, since the analog to digital converter  120  and the operating control unit  122  are operative in the active mode all the time, the power efficiency is therefore relatively poor. In comparison, the average power consumed by the touch panel control device  20  of the present invention is measured and accounts for about 30%-50% of power consumed by the control device  12  of the prior art; this is equally to say that the standby time of the present invention is about 2 to 3 times longer than that of the prior art—the advantage in power saving by the present invention is therefore obvious. 
     Briefly speaking, according to the present invention, the touch panel control method and device comprises a buffer memory, which is connected between the analog to digital conversion unit and the operation unit, for data buffering. Also, according to the present invention, the touch panel control method and device comprises a load parameter storing unit, such that the analog to digital conversion unit can access the capacitive load parameters directly from the load parameter storing unit. The present invention also utilizes a mode control unit to orderly make the operation unit and the analog to digital conversion unit settled in a sleep mode, such that the electric power can be saved and the efficiency can be improved. 
     To make a summary, according to the present invention, the touch panel control device improves the overall efficiency of the touch panel device by utilizing a novel touch panel control method and device architecture. Also, according to the experiment, the touch panel control method and the device architecture disclosed by the present invention can effectively perform the touch panel function, and reduce the power consumption of the touch panel device, and the consumer benefits can be advanced by extending the standby time of the touch panel device. 
     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.