WO2008038239A2

WO2008038239A2 - Processing a signal from a pointing device sensor

Info

Publication number: WO2008038239A2
Application number: PCT/IB2007/053914
Authority: WO
Inventors: Sasa Ristic; Jeroen C. R. A. Korsten
Original assignee: Nxp B.V.
Priority date: 2006-09-29
Filing date: 2007-09-26
Publication date: 2008-04-03
Also published as: WO2008038239A3

Abstract

An integrated circuit (400) for processing a signal from a pointing device sensor comprises an input (414) for receiving the signal; a signal processing circuitry (404) for detecting a feature in the signal indicative of a touch or click; and decision circuitry (408) for establishing whether a time interval between a first touch or click detected by the signal processing circuitry and a second touch or click detected by the signal processing circuitry is not longer than a maximum time interval. The pointing device sensor may be comprised in a touch screen. Additional circuitry (410) for extracting coordinates representing a position where the touch screen is touched; and circuitry for detecting a feature in the signal indicative of a touching movement along the touch screen is provided.

Description

PROCESSING A SIGNAL FROM A POINTING DEVICE SENSOR

FIELD OF THE INVENTION

The invention relates to processing a signal from a pointing device sensor.

BACKGROUND OF THE INVENTION

Touch screens are widely used as a human interface in devices such as mobile phones, PDAs, and gaming devices. Typically an application running on such a device performs certain operations in dependence on touch events generated by the touch screen in response to a human touching the touch screen with his finger or with a stylus. Such a touching of the screen is also referred to as tapping the screen. Different operations are performed in dependence on how the touch screen is touched or tapped. A single touch may be interpreted as pressing a command button or as selecting an icon. A moving touch may be interpreted as dragging an icon. A double touch (touching the screen two times in repetition within a short time interval) can be interpreted as a command to open a folder associated with an icon or to open a document or application associated with an icon. This way, different application operations can be associated with a single touch, a double touch, and a moving touch.

A currently used type of touch-screen interface devices involved in hand- held personal devices is described in "Fast interface electronics for a resistive touch-screen" by Aguilar, R.N. and Meijer, G. C. M., in Sensors, 2002, Proceedings of IEEE, Vol. 2, pages 1360- 1363, referred to hereinafter by "Aguilar et al.". Such a device typically comprises three functional blocks: An analogue interface circuit that switches on the required plates' biasing; an A/D converter mostly successive-approximation algorithm based; and an interface logic block that connects the device with the rest of the system. The system controller executes the application-level software routine that configures and controls the touch-screen data acquisition. More recently, some design solutions promote a buffered data handling, and also an interrupt-based handshake on the lower protocol layers. On the application protocol level, the raw coordinate data or pen-pressure data is interpreted based upon the rate of conversion-start commands and based on the data values themselves, and optionally on the pen-down interrupt event. This way, a single touch action is interpreted and identified by coordinates, and it triggers the assigned application-level function.

SUMMARY OF THE INVENTION

It would be advantageous to have an improved way of processing a signal from a pointing device sensor. To better address this concern, in a first aspect of the invention an integrated circuit is presented that comprises: an input (414) for receiving the signal from the pointing device sensor; - signal processing circuitry (404) for detecting a feature in the signal indicative of a touch or click; decision circuitry (408) for establishing whether a time interval between a first touch or click detected by the signal processing circuitry and a second touch or click detected by the signal processing circuitry after the first touch or click is not longer than a predetermined maximum time interval; and an output (416) for providing a notification of the second touch or click in dependence on a result of the decision circuitry.

By using the proposed integrated circuit, the system controller or central processing unit needs to spend only very little processing capacity and/or communication capacity on the detection of the double touch event. The double touch event is detected by the circuitry of the proposed integrated circuit, and the controller or processor receives notification of a double touch event by means of an output of the integrated circuit. An integrated circuit as proposed can also be used in conjunction with a mouse device for processing a signal corresponding to a mouse button, or in conjunction with a touchpad (often used in laptops) or a tablet (often used in conjunction with graphic design applications).

In an embodiment, the pointing device sensor is comprised in a touch screen (106).

The proposed integrated circuit can be incorporated to advantage in a device using a touch screen as an input device. In the case where the touch screen is part of a mobile device, such as a mobile phone or a PDA, the reduction of needed processor capacity and communication capacity is especially relevant. Also for gaming devices which require a quick response to user input, the integrated circuit can be used to advantage.

An embodiment comprises: circuitry (410) for extracting coordinates representing a position where the touch screen is touched; and circuitry for detecting a feature in the signal indicative of a touching movement along the touch screen. These are other relevant features of an integrated circuit for processing a signal from a touch screen. Outputs corresponding to the detected features as well as corresponding to a single touch event may also be provided.

An embodiment comprises a second input (418) for receiving a value indicative of the maximum time interval. This feature makes the integrated circuit more flexible as it allows a configuration of the maximum double click time interval.

In an embodiment, the output comprises a signal indicative of whether the time interval is longer than the maximum time interval.

This is a convenient way of enabling a processor to execute different commands depending on whether a single touch event or a double touch event occurred. Both events may also be used to trigger an interrupt on the controller or processor.

In an embodiment, the time interval between the first touch or click and the second touch or click is measured as the time interval between an end of the first touch or click and a beginning of the second touch or click. Alternatively, the time interval between the first touch or click and the second touch or click is measured as the time interval between a begin of the first touch or click and a begin of the second touch or click.

In an embodiment, the decision circuitry (408) comprises: circuitry for increasing a counter at regular intervals; and - a comparator for comparing the counter with a value corresponding to the maximum time interval, upon detecting the second touch or click by the signal processing circuitry.

This is a particularly efficient way of implementing the integrated circuit.

In an another aspect of the invention a method is provided, which is to be applied in an integrated circuit for processing a signal from a pointing device sensor, the method comprising: receiving the signal from the pointing device sensor; detecting a feature in the signal indicative of a first touch or click; detecting a feature in the signal indicative of a second touch or click after the first touch or click; establishing whether a time interval between the first touch or click and the second touch or click is not longer than a predetermined maximum time interval; and - providing a notification of the second touch or click in dependence on a result of the establishing.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the invention will be further elucidated and described with reference to the drawing, in which:

Fig. 1 illustrates a touch screen interface circuit;

Fig. 2 illustrates a sequence-flag maintenance flow diagram;

Fig. 3 illustrates exemplary timing diagrams of the sequence flag handling; and

Fig. 4 illustrates an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS Currently used touch-screen interface devices involved in hand- held personal devices, make use of three functional blocks: An analogue interface circuits that switches on the required plates' biasing; An A/D converter (ADC) mostly successive-approximation algorithm based; An interface logic block that connects the device with the rest of the system. A system controller, for example a programmable processor, executes the application-level software routine that configures and controls the touch-screen data acquisition. The mechanism of polling, which is in most cases the method involved, is heavily using the (serial) interface bandwidth, and requires a high level of protocol data exchange. In order to solve the communication bottleneck, some design solutions promote a buffered data handling, and also an interrupt-based handshake on the lower protocol layers. On the higher application protocol level, the raw coordinate or pen pressure data is processed/interpreted based upon the ADC's sampling rate, then, based on the coordinates themselves, and optionally on the pen-down interrupt event. This way, a single touch action is interpreted and identified by coordinates, and it triggers the assigned application-level function. Similarly, a "double touch" command, which triggers another assigned function for the closed coordinate values, could be interpreted as well. Regarding application-level enhancements, the user's double-touch action may be detected by means of hardware.

Existing methods for the "double-touch" function detection make use of software/driver procedures, depending heavily on software timers. This approach dramatically decreases the main processor capacity available for applications due to the fact that in all personal devices, the touch-screen human-interface has a high service priority. By performing the double-touch function detection in hardware in a modified touch-screen interface IC, the main processor performance is increased. It is possible to keep full flexibility with respect to the double-touch time criteria parameter. Fig. 1 shows a diagram of selected elements occurring in for example a conventional mobile phone, PDA, gaming device, or computer with a touch screen. The Figure shows a system controller/processor 102, a touch-screen interface circuit 104, and a touch screen 106.

The touch screen 106 is a conventional 4-wire resistive-net based touch-screen device. A 5-wire resistive-net based touch-screen device or any other type of touch screen device could have been used instead. Examples of such touch-screen devices are described in Aguilar et al.. Such touch screen sensors are available on the market and within reach of the skilled person, and will be described herein only briefly. The touch screen display 106 comprises a bottom layer 118 connected to wires TSPY and TSMY and a top layer 120 connected to wires TSMX and TSPX. These wires are connected to analogue touch-screen switching matrix 110 of interface circuit 104 for biasing the passive touch-screen device. Switching matrix 110 is connected to ADC 108 and to control/buffer/interface 114 for communicating the pen-down/up discontinuity events as indicated by arrow 124. AD conversion can be of any type and resolution, although a certain minimal sampling rate is recommended to obtain a good response time. In existing devices the sampling rate varies from 100Hz till several kHz, while 10-bit successive approximation conversion and a ratio- metric measurement approach look to be quite common.

The system provides an interface 112 across which the operation mode is controlled, the sampling rate is programmed, the double-touch criteria are set including the maximum double touch interval as a function (number) of sampling periods, and the produced information about (single-touch, double-touch) events is read. Part of the interface can be optionally an interrupt line 116 directly connected to the system controller/processor, reporting a single-touch or double-touch event. In an embodiment, the processor 102, the touch-screen interface circuit 104, and the touch screen 106 are incorporated in a single device, for example a mobile phone.

In an embodiment, the touch-screen interface circuit 104 and the touch screen are comprised in a single device, the device being arranged for communicating with another apparatus (such as a computer) comprising the processor 102. In this embodiment, interface 112 could comprise a wireless (e.g. Bluetooth) or wired (e.g. USB) interface.

In the following, the object touching the screen is referred to as "pen". The event corresponding to a user starting to touch the touch screen with for example his finger or with a stylus is referred to as a "pen-down" event. The event corresponding to a user ceasing to touch the touch screen is referred to as a "pen-up" event. The terms pen, pen-down and pen-up are used regardless of the type of object (e.g. finger, stylus) that is touching the screen.

Fig. 2 shows an example flow of the processing steps involved in an implementation of double-touch event detection. These processing steps may be implemented in double-touch detector 122 of the control/buffer/interface 114. The processing steps involve setting and reading a sequence flag and a sequence bit, whose roles will become apparent in the following. In idle mode 202, the system waits for a pen-down event. The pen-down event is detected by the analogue interface circuit or switching matrix 110, and digitally filtered (de-bounced) in order to eliminate some short (false) touch triggers. This way filtered, the pen-down event 224 triggers a sequence of processing steps as follows. First the sequence flag is inverted (step 204) and the sequence bit is inverted (step 206). After that, coordinate conversion is performed (step 208), this is to compute the x and y coordinates of the pen on the touch screen 106. Before and after coordinate conversion, the sequence bit is inverted (steps 228 and 230). After and during the coordinate conversion 208, it is checked (in step 210) whether a pen-up event has occurred, and if so the idle mode is again assumed (step 212). Also, after this the sequence flag is given the value of the sequence bit (in step 214), and the coordinate values are stored (in step 216) along with the sequence flag value in storage. The conversion is further paced (in step 218) by a sampling rate timer, to repeatedly perform coordinate conversion while the pen is continuously touching the screen. This sampling rate timer 218 is interrupted when a pen-up is detected (in step 220), and the idle mode is again assumed (step 222).

As shown in Fig. 2, each time a pen-down event is detected, a bit called sequence-bit (sb) designator, gets toggled (inverted) (step 206). After data conversion (step 208), for which reading was disabled, in the following sampling delay interval (steps 218- 220), reading of data is allowed. The outcome of the sequence-flag maintenance process is: It takes one value at pen-down event, and keeps it unchanged during reading-enabled period, i.e. during the sampling rate time-out. Next to it, there are two continuous conversion- breaking scenarios. First, if a pen-up event comes while a conversion is running, the conversion proceeds till completion, however, data is not buffered, nor is the sequence flag updated. Next time at pen-down event, the sequence bit and sequence flag will get the inverted value. Second, if a pen-up event comes during the sampling time-out period, data including the sequence flag information is nevertheless validated and buffered, therefore the sequence bit is again ready for the next pen-down event. The occurrence of a double touch event can be communicated to for example a processor or controller by means of an interrupt indicating occurrence of a "double-touch event" (dtf int). Alternative ways of providing this information include using a status flag (dtf) may be used to indicate that a double touch event has occurred, or sending a digital message to the processor. One way of determining the double touch event is to approximate the time for which the sequence flag keeps a unique value. For this purpose, a counter is involved, (Double-Touch Counter - DTC in Fig. 3). This counter is increased when the sampling rate time-out timer has expired (step 218), and reset when the sequence flag (SF) is toggled. In the moment of toggling the sequence flag, if the DTC value is less then a predefined maximum double-touch delay value, the double touch event is said to be detected, and therefore the double-touch flag (dtf) is set to one, otherwise it is reset to zero.

In Fig. 3, the sequence flag maintenance timing is shown for two possible scenarios according to the flow diagram of Fig. 2. In the example shown in Fig. 3, it is assumed that the predefined maximum double-touch delay corresponds to a DTC value of at least 3. The Figure shows timelines of the state of pen-down (PD), sequence bit (SB), sequence flag (SF), and the state of the control flow according to the flow diagram of Fig. 2. Here, CONV refers to the X and Y conversion step 208 and DEL refers to the delay of the iteration 218-220. Timelines 302 show the first scenario. A pen-down event occurs when the pen-down state (PD) changes from low to high. A pen-up event occurs when the pen-down state (PD) changes from high to low. The pen-down event 308 triggers the state changes as discussed with reference to Fig. 2, including a toggle of the sequence flag (SF). The pen-up event 310 causes a change to the idle mode (step 220). The subsequent pen-down event 312 again causes a toggle of the sequence flag (SF).

Timelines 304 show the second scenario. The pen-down event 314 causes similar changes as pen-down event 308. The pen-up event 316 occurs during X and Y conversion (CONV). This again causes a return to the idle mode, and the subsequent pen- down event 318 causes a toggle of the sequence flag (SF).

Timelines 306 may be viewed in conjunction with either timelines 302 or 304. It shows the pulses produced by the double-touch counter clock (DTC cIk), the double touch counter reset (DTC rst) pulses that are produced in reaction to the pen-down event 308 or 314. The double touch counter DTC is increased after every pulse of DTC cIk and is reset after every pulse of DTC rst. After the second pen-down event 312 or 318, the sequence flag SF is toggled 320, a DTC rst pulse 322 is produced, and, because DTC is smaller than the maximum DTC value, the double touch flag dtf is set. This flag may be an output of an integrated circuit, trigger an interrupt, or be used otherwise to communicate a double-touch event to for example a processor.

Fig. 4 shows an embodiment of a control/buffer/interface IC 400. The IC 400 comprises an input 414 for receiving the signal from the pointing device sensor. The signal is distributed by an interface 402 to a circuitry 404 for detecting a feature in the signal indicative of a touch. Ways to determine such a feature in the signal are known in the art. Each time such a feature is detected by circuitry 404, a trigger is sent to a decision circuitry 408 which is used for establishing whether a double touch has occurred, by checking whether a time interval between two successive touches is not longer than a predetermined maximum time interval. The maximum time interval may for example be 100 ms, or 300 ms. The maximum time interval may also be expressed using a different unit, for example as a number of clock pulses. If the double touch event has been detected, a notification of a 'double touch' is provided to output 416 via interface circuitry 412. An input 418 may be connected to the decision circuitry 408 to allow configuration of the maximum time interval. Additional circuitry 410 may be provided for extracting coordinates representing a position where the touch screen is touched. Additional circuitry 410 may also be arranged for detecting a feature in the signal indicative of a touching movement along the touch screen.

Decision circuitry 408 maintains a counter which is increased at regular time intervals. This counter is reset upon detection of the first touch by circuitry 404. Upon detection of the second touch by circuitry 404, it is checked by circuitry 408 whether the counter is larger than the counter value corresponding to the predetermined maximum time interval. If this is the case, a 'single' touch is reported to interface 412 and consequently to output 416. If the counter is smaller than or equal to the counter value corresponding to the predetermined maximum time interval, a 'double' touch is reported to interface 412 and consequently to output 416. After each touch event the counter is reset. Alternatively, the counter is not reset, but the counter value corresponding to a touch is stored, and upon receiving the signal that a second touch is detected, the current counter value is compared to the stored counter value in order to establish the time interval between the two touches.

The counter value may be reset/stored at a pen-down event, but alternatively at a pen-up event. In the latter case, the time interval measured is the time interval during which the screen was not touched.

The double-touch functionality can be fully performed by HW (a touch-screen interface circuit), and provide an output indicative of the double touch event. Alternatively, some of the processing may be performed in HW, and another part of the processing may be done on the processor or controller.

Since the proposed method is implemented in an IC, it can be used in applications involving a touch-screen device on the human- interface side, and a standard programming interface on the processor-based system side. Typical applications include (3G) mobile phones, PDAs, and gaming devices, especially those comprising a touch-screen human interface. Although the description has focused on the processing of touch screen signals, a skilled person will be able to extend the method to other pointing devices, including a touch pad commonly used in laptops, and a mouse pointer device commonly used as input device for personal computers. In the case of a mouse pointer, the pen-down event is replaced by a mouse-button-down event and a touch is replaced by a click. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

CLAIMS:

1. An integrated circuit (400) for processing a signal from a pointing device sensor, comprising: an input (414) for receiving the signal from the pointing device sensor; signal processing circuitry (404) for detecting a feature in the signal indicative of a touch or click; decision circuitry (408) for establishing whether a time interval between a first touch or click detected by the signal processing circuitry and a second touch or click detected by the signal processing circuitry after the first touch or click is not longer than a predetermined maximum time interval; and - an output (416) for providing a notification of the second touch or click in dependence on a result of the decision circuitry.

2. The integrated circuit according to claim 1, wherein the pointing device sensor is comprised in a touch screen (106).

3. The integrated circuit according to claim 0, further comprising: circuitry (410) for extracting coordinates representing a position where the touch screen is touched; and circuitry for detecting a feature in the signal indicative of a touching movement along the touch screen.

4. The integrated circuit according to claim 1, where the output is arranged for being connected to a central processing unit or controller (102).

5. The integrated circuit according to claim 1, further comprising a second input

(418) for receiving a value indicative of the maximum time interval.

6. The integrated circuit according to claim 1, wherein the output comprises a signal indicative of whether the time interval is longer than the maximum time interval.

7. The integrated circuit according to claim 1, wherein the time interval between the first touch or click and the second touch or click is measured as the time interval between an end of the first touch or click and a beginning of the second touch or click.

8. The integrated circuit according to claim 1, wherein the decision circuitry (408) comprises: circuitry for increasing a counter at regular intervals; and a comparator for comparing the counter with a value corresponding to the maximum time interval, upon detecting the second touch or click by the signal processing circuitry.

9. The integrated circuit according to claim 0, wherein the decision circuitry (408) further comprises: - counter reset circuitry for resetting the counter after the comparing by the comparator.

10. A portable device comprising: a touch screen (106) for generating a touch signal; - a processor (102); an integrated circuit according to claim 1 whose input is connected to the touch screen for receiving the touch signal and whose output is connected to the processor.

11. A touch screen device comprising: - a touch screen (106) for generating a touch signal; an integrated circuit according to claim 1 whose input is operative to receive the touch signal; an interface (112) for connecting the output of the touch screen interface IC to a processor.

12. A method to be applied in an integrated circuit for processing a signal from a pointing device sensor, comprising: receiving the signal from the pointing device sensor; detecting a feature in the signal indicative of a first touch or click; detecting a feature in the signal indicative of a second touch or click after the first touch or click; establishing whether a time interval between the first touch or click and the second touch or click is not longer than a predetermined maximum time interval; and - providing a notification of the second touch or click in dependence on a result of the establishing.