Control circuit of resistive touch panel
11360606 · 2022-06-14
Assignee
Inventors
Cpc classification
G06F2203/04104
PHYSICS
G06F3/045
PHYSICS
International classification
Abstract
A control circuit controls a two-wire resistive touch panel. The two-wire resistive touch panel includes a first region and a second region which are adjacent to each other in a coordinate axis direction (X direction), and the first region has resistance per unit length lower than resistance per unit length of the second region. A measurement unit measures an electric signal having a correlation with impedance between two wires which are lead out from the resistive touch panel. A processing unit (i) determines that the first region is touched when the electric signal or the impedance obtained from the electric signal is included in a predetermined first range, (ii) determines that the second region is touched when the electric signal or the impedance obtained from the electric signal is included in a predetermined second range, and generates a touched coordinate.
Claims
1. A control circuit of a resistive touch panel, the resistive touch panel including a first sheet and a second sheet which overlap each other and extend in a coordinate axis direction, and the first sheet including a first region and a second region which are adjacent to each other in the coordinate axis direction, wherein resistance per unit length of the first sheet in the first region is higher than resistance per unit length of the first sheet in the second region, the control circuit comprising: a measurement unit structured to measure an electric signal being inversely proportional to impedance between a first line which is lead out from one end of the first sheet and a second line which is lead out from one end of the second sheet; and a processing unit structured to: (i) determine that the first region is touched when the electric signal is included in a predetermined first range; (ii) determine that the second region is touched when the electric signal is included in a predetermined second range; and generate a touched coordinate.
2. The control circuit according to claim 1, wherein the measurement unit includes: a resistor connected to the resistive touch panel in series; a voltage source structured to apply a predetermined voltage across a series connection of the resistive touch panel and the resistor; and an A/D converter structured to measure a voltage at a connection node between the resistive touch panel and the resistor.
3. The control circuit according to claim 1, wherein the measurement unit includes: a current source structured to supply constant electric current to the resistive touch panel; and an A/D converter structured to measure voltage drop of the resistive touch panel.
4. The control circuit according to claim 1, wherein the resistive touch panel has a shape that is curved or bent in a plane such that two places having different coordinates are located close to each other, the control circuit further includes a two-point touch detector structured to generate a two-point touch detection signal indicating whether or not two points are simultaneously touched, and when the two-point touch detection signal indicates that two points are simultaneously touched, output of the processing unit is invalidated.
5. A touch input device comprising: a resistive touch panel: and the control circuit according to claim 1, structured to control the resistive touch panel.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which:
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DETAILED DESCRIPTION
(16) The disclosure will now be described based on preferred embodiments which do not intend to limit the scope of the present disclosure but exemplify the disclosure. All of the features and the combinations thereof described in the embodiment are not necessarily essential to the disclosure.
(17) Embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings in which like numerals represent like elements throughout the several figures, and in which example embodiments are shown. Embodiments of the claims may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. The examples set forth herein are non-limiting examples and are merely examples among other possible examples.
(18) In the present specification, “a state where a member A is coupled to a member B” includes not only a case where the member A is physically directly coupled to the member B but also a case where the member A and member B are indirectly coupled via another member that does not substantially affect an electric coupling state therebetween or does not impair functions and effects provided by coupling the members.
(19) Similarly, a state represented by “a member C is provided between the member A and the member B” includes not only a case where the member A is directly coupled to the member C or the member B is directly coupled to the member C but also a case where the member A is indirectly coupled to the member C or the member B is indirectly coupled to the member C via another member that does not substantially affect an electric connection state therebetween and does not impair functions and effects provided by coupling the members.
(20) First, a principle of three-wire and two-wire resistive touch panels will be described.
Three-Wire Resistive Touch Panel
(21)
(22) When a user touches a point P, the two sheets 402 and 404 contact each other at the point (hereinafter referred to as a contact point) P. A control circuit 200T applies: a predetermined power supply voltage (first fixed voltage) V.sub.DD to one of the two wires X.sub.1 and X.sub.2 of the sheet 402; and a ground voltage (second fixed voltage) V.sub.GND (=0 V) to the other wire thereof. A voltage V.sub.P at the contact point P is represented by Expression (1).
V.sub.P=V.sub.DD×R.sub.X2/(R.sub.X1+R.sub.X2) (1)
(23) A resistance value R.sub.X1 is a resistance value between the contact point P and one end of the sheet 402, and a resistance value R.sub.X2 is a resistance value between the contact point P and the other end of the sheet 402. R.sub.X1+R.sub.X2 is a resistance value across the sheet 402 and is a constant. R.sub.C represents contact resistance.
(24) Assuming that the sensing wire S on the sheet 404 side has high impedance, the voltage V.sub.P at the contact point P is generated in the sensing wire S. The control circuit 200T determines the resistance value R.sub.X2, that is, an X coordinate by measuring the voltage V.sub.P at the sensing wire S.
(25) The sheet 404 may also be a conductor.
Two-Wire Resistive Touch Panel
(26)
(27) To detect an X coordinate, the control circuit 200T measures impedance Z (referred to as the panel impedance) in a path from the wire X to the wire F via a contact point P.
Z=R.sub.X+R.sub.C+R.sub.X′
(28) Since both R.sub.X and R.sub.X′ are linearly changed with respect to the X coordinate and R.sub.C is a constant, the panel impedance Z is represented by a linear function of the X coordinate, and the linear function is known. Therefore, the X coordinate corresponding to the panel impedance Z can be detected by measuring the panel impedance Z. Note that the sheet 404 may also be a metal conductor, and in this case, R.sub.X′=0 is established.
(29) Next, touch input devices 100A to 100D respectively using the above-described two-wire/three-wire resistive touch panels will be described on the basis of some embodiments.
First Embodiment
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(32) The control circuit 200A includes a measurement unit 210A and a calculator 230A. The measurement unit 210A applies a predetermined voltage between two wires X.sub.1 and X.sub.2 of the three-wire resistive touch panel 400T. Then, the measurement unit 210A measures a voltage (sense voltage) V.sub.S of a sensing wire S in this state. For example, the measurement unit 210A includes a driver circuit 212 and an A/D converter 214. The driver circuit 212 may apply a predetermined power supply voltage V.sub.DD to a first wire X.sub.1 and a ground voltage V.sub.GND (0 V) to the second wire X.sub.2. The A/D converter 214 converts the sense voltage V.sub.S into a digital value D.sub.S. An amplifier may also be provided in a pre-stage of the A/D converter 214.
(33) The calculator 230A generates a coordinate X of a contact point on the basis of the sense voltage V.sub.S.
(34) When a distance between the two regions RGN1 and RGN2 is sufficiently wide, whether input is made to the button 102 or the slider input unit 104 can be discriminated by the above-described processing. However, when the button 102 and the slider input unit 104 are located close to each other and a sufficient space cannot be secured between the two regions RGN1 and RGN2, it is difficult to discriminate whether the input is made to the button 102 or the slider input unit 104. For example, even in a case where touch input is made to the region RGN1, the touch input may be erroneously determined as the input to the region RGN2 due to influence of noise. Also, in a case where the space is narrower than a width of a finger, the detected X coordinate may reciprocate between the regions RNG1 and RGN2 depending on a position of the finger, erroneous operation may be caused.
(35) Such problems can be solved by combining a three-wire resistive touch panel 400T of
(36)
Ru.sub.1<<Ru.sub.2
(37) Note that a direction of an X coordinate and a method of setting an origin thereof are merely examples.
(38)
(39) Operation at the time of using the conventional panel will be described with reference to the dash-dot-dash line in order to clarify advantages of the three-wire resistive touch panel of
V.sub.S≈Ru.sub.3×X
(40) Assume that the two regions RGN1 and RGN2 are defined as illustrated in the drawing and a space (dead zone) ΔX exists therebetween. In the conventional panel, δV is to be a voltage range corresponding to the space.
δV=ΔX×Ru.sub.3
(41) Next, advantages of the three-wire resistive touch panel of
ΔV=ΔX×Ru.sub.2
(42) Here, when a relation Ru.sub.1<Ru.sub.3<Ru.sub.2 is established, ΔV>δV can be achieved. That is, the voltage range corresponding to the dead zone is expanded. This means that in a case where the space between the button 102 and the slider input unit 104 is narrow, it becomes easy to determine whether input is made to the button 102 or the slider input unit 104.
(43) Furthermore, with the use of the three-wire resistive touch panel of
(44) Refer to
(45) Additionally, the calculator 230A determines that (ii) the slider input unit 104 corresponding to the second region A2 is touched when the voltage V.sub.S of the sensing wire is included in a predetermined second range (the voltage range ΔV.sub.H on the predetermined power supply voltage V.sub.DD side in
(46) Consequently, it is possible to easily and surely discriminate the input to the button 102 from the input to the slider input unit 104.
Second Embodiment
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(48) The control circuit 200B includes a measurement unit 210B and a calculator 230B. The measurement unit 210B is capable of measuring an electric signal (sense signal V.sub.S) having a correlation with panel impedance Z between two wires X and S of the two-wire resistive touch panel 400D. The calculator 230B includes an impedance measurement circuit 216 and an A/D converter 218. The impedance measurement circuit 216 generates the sense signal V.sub.S having the correlation with the panel impedance between the two wires X and S.
(49) The A/D converter 218 converts the sense signal V.sub.S into a digital value D.sub.S. The calculator 230B receives the digital value D.sub.S of the measured sense signal, also determines whether input is made to a button 102 or a slider input unit 104, and outputs a coordinate X in a case where the input is made to the slider input unit 104. Similar to a calculator 230A of
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(51) The sense voltage V.sub.S at a connection node between the two-wire resistive touch panel 400D and the resistor R.sub.B (that is, voltage drop at the resistor R.sub.B) is received as a sense signal in the A/D converter 218. The sense signal V.sub.S at this time is represented by Expression below and has the correlation with the panel impedance Z of the two-wire resistive touch panel 400D.
V.sub.S=V.sub.DD×R.sub.B/(Z+R.sub.B)
(52) As described above, since the panel impedance Z of the two-wire resistive touch panel 400D has a one-to-one correspondence with the coordinate X, the measured sense signal V.sub.S also has a one-to-one correspondence with the coordinate X.
(53) Note that the voltage drop of the two-wire resistive touch panel 400D may also be deemed as the sense signal. The sense signal V.sub.S at this time is represented by Expression below and has the correlation with the panel impedance Z of the two-wire resistive touch panel 400D.
V.sub.S=V.sub.DD×Z/(Z+R.sub.B)
(54) In the measurement unit 210B of
V.sub.S=I.sub.C×Z
(55) Note that an amplifier may also be provided at an input side of the A/D converter 218.
(56)
Ru.sub.1<<Ru.sub.2
(57) Note that a direction of an X coordinate and a method of setting an origin thereof are merely examples.
(58)
(59) Next, advantages of the two-wire resistive touch panel of
ΔV=ΔX×Ru.sub.2
(60) Similar to the description of the three-wire resistive touch panel, when a relation of Ru.sub.1<Ru.sub.3<Ru.sub.2 is established, ΔV>δV can be achieved. That is, the voltage range corresponding to a dead zone is expanded. Due to this, even in a case where the space between the button 102 and the slider input unit 104 is narrow, it also becomes easy to discriminate whether the input is made to the button 102 or the slider input unit 104.
(61) Furthermore, a voltage range ΔV.sub.H of the sense voltage V.sub.S corresponding to the region RGN2 can be expanded more than a voltage range δV.sub.H of the conventional panel by using the two-wire resistive touch panel of
(62) Refer to
(63) Also, the calculator 230B determines that (ii) the second region RGN2 is touched when the sense signal V.sub.S or the panel impedance Z obtained therefrom is included in the predetermined second range (voltage range ΔV.sub.H in
(64) Thus, according to the second embodiment also, the effects similar to those of the first embodiment can be obtained.
(65) In the above, the cases where the three-wire resistive touch panel 400T and two-wire resistive touch panel 400D each having a straight shape have been described above, but the three-wire resistive touch panel 400T and two-wire resistive touch panel 400 are not limited thereto and may have a curved shape or a bent shape in a plane. In this case, the X axis can be defined along a panel extending direction. Hereinafter, such a panel will be referred to as a curved panel.
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(67) A curved panel 500D in
(68) The curved panels 500T and 500D in
(69) A problem that may occur in such panels will be described. In such panels, the two places (X.sub.A and X.sub.B) having different coordinates may be simultaneously touched as illustrated in
Third Embodiment
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(71) The measurement unit 210C can have a configuration similar to that of a measurement unit 210A already described above. The calculator 230C determines a coordinate on the basis of a sense voltage V.sub.S.
(72) The two-point touch detector 250 generates a two-point touch detection signal DT indicating whether or not two points are simultaneously touched. Note that a technology disclosed in Japanese Patent No. 5086394 can be used to detect whether or not the two-simultaneous touch is performed. More specifically, the two-point touch detector 250 can determine a distance between two points on the basis of panel electric current I.sub.P flowing through the curved panel 500T. Note that the method of detecting a two-point touch is not limited thereto and another method may also be used.
(73) In the touch input device 100C, when the two-point touch detection signal DT indicates that the two points are simultaneously touched, output of the calculator 230C (i.e., an X coordinate) is invalidated.
(74) According to the touch input device 100C, it is possible to prevent erroneous determination of a coordinate in the event of the two-simultaneous touch on the curved panel 500T.
Fourth Embodiment
(75)
(76) The measurement unit 210D can have a configuration similar to that of a measurement unit 210B already described above. The calculator 230D determines a coordinate on the basis of a sense voltage V.sub.S.
(77) The two-point touch detector 250 generates a two-point touch detection signal DT indicating whether or not two points are simultaneously touched. In the touch input device 100D, when the two-point touch detection signal DT indicates that the two points are simultaneously touched, output of the calculator 230D (i.e., an X coordinate) is invalidated.
(78) According to this touch input device 100D, it is possible to prevent erroneous determination of a coordinate in the event of a two-simultaneous touch on the curved panel 500D.
(79) In the above, the present disclosure has been described on the basis of the embodiments. Note that the embodiments are examples and it should be understood by those skilled in the art that: various modified examples can be achieved by combining the respective constituent elements and the processes of the processing thereof; and such modified examples are also included in the scope of the present disclosure. Hereinafter, such modified examples will be described.
First Modified Example
(80) The first embodiment and the third embodiment can be combined. Furthermore, the second embodiment and the fourth embodiment may also be combined.
Second Modified Example
(81) In the first and second embodiments, the resistance value Ru.sub.1 per unit length on the button 102 side is made small and the resistance value Ru.sub.2 on the slider input unit 104 side is made large, respectively, but not limited thereto. The impedance distribution may be determined in accordance with: a position of a sense signal measured to detect a coordinate: and a measurement method. Specifically, the impedance distribution is to be determined such that position sensitivity of a sense signal is low on the button 102 side and position sensitivity of a sense signal is high on the slider input unit 104 side.
Third Modified Example
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Fourth Modified Example
(83) In the first and second embodiments, the multifunctional touch input device 100 including the button 102 and the slider input unit 104 has described, but the combination of the functions is not limited thereto.