CONTROL METHOD AND ELECTRONIC STYLUS FOR TOUCH INPUT TO A CAPACITIVE TOUCHPAD MODULE
An electronic stylus emits an excitation signal to apply to a trace of a capacitive touchpad module near a touch point when the electronic stylus touches the capacitive touchpad module, so as to change a waveform of a charging/discharging signal in the trace, and depending on the waveform variation, the capacitive touchpad module can identify the touch point.
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This application is a Continuation of and claims priority benefits to U.S. patent application Ser. No. 12/651,575, filed 4 Jan. 2010, now pending, which claims priority benefits to U.S. Provisional Patent Application Ser. No. 61/142,690, filed 6 Jan. 2009.
FIELD OF THE INVENTIONThe present invention is related generally to an apparatus for touch input and, more particularly, to an electronic stylus for a capacitive touchpad module.
BACKGROUND OF THE INVENTIONCurrently, the mainstream touch control technologies include capacitive touch sensing and resistive touch sensing, of which the resistive touch sensing technology may be further divided into four-wire resistive touch sensing, five-wire resistive touch sensing and eight-wire resistive touch sensing. A resistive touch sensor is constructed mainly by an indium tin oxide (ITO) glass plate, an ITO thin film, and a spacer for separating the ITO glass plate from the ITO thin film. When a finger, a stylus or another medium touches on a resistive touch sensor, it will cause a short-circuit between the ITO glass plate and the ITO thin film at the touch point and thereby induce a voltage drop, so that the touch point can be sensed responsive to the voltage drop. For capacitive touch input, it may be classified into surface capacitance touchpad module and projected capacitance touchpad module. A capacitive touchpad module may include an ITO, a membrane, a printed circuit board (PCB), or a flexible printed circuit (FPC) board. When a finger or a conductor touches on a capacitive touchpad module, it will cause a capacitance variation at the touch point and thereby the touch point can be sensed accordingly.
As the capacitive touch sensing does not rely on deformation of a sensor to sense the touch point, it is impossible to use a stylus with a capacitive touchpad module, as does for the resistive touch sensing. Even if the tip of a stylus were replaced with a conductor, it would still be impossible for the stylus to induce a sufficient capacitance variation of a trace of the capacitive touchpad module because of the too-small size of the tip. Although this problem may be solved by enlarging the tip of a stylus, the tip, after being enlarged, would become as thick as a finger, which is unfavorable for such applications as handwriting recognition and drawing in a small-sized capacitive touchpad module. Moreover, capacitive touch sensors used in cell phones or notebook computers are usually provided with a plurality of virtual buttons, which are made to be very small and located very close to each other, so it is impossible to correctly click such virtual buttons by use of a stylus having a large tip.
Therefore, it is desired a novel stylus having a small tip for capacitive touch input.
SUMMARY OF THE INVENTIONAn object of the present invention is to provide an apparatus and a control method thereof for touch input.
Another object of the present invention is to provide an electronic stylus and a method thereof for touch input.
A further object of the present invention is to provide a capacitive touchpad module and a control method thereof for touch input.
According to the present invention, an apparatus for touch input includes a capacitive touchpad module and an electronic stylus. When the electronic stylus touches the capacitive touchpad module, the electronic stylus emits an excitation signal to apply to a trace of the capacitive touchpad module near a touch point, so as to change a waveform of a charging/discharging signal in the trace. Therefore, the capacitive touchpad module can identify the touch point depending on the waveform variation.
According to the present invention, a control method for an apparatus for touch input includes providing an excitation signal for an electronic stylus, emitting the excitation signal by the electronic stylus to apply to a trace of a capacitive touchpad module near a touch point when the electronic stylus touches the capacitive touchpad module, so as to change a waveform of a charging/discharging signal in the trace, and sensing the touch point according to a variation of the waveform.
According to the present invention, an electronic stylus for touch input to a capacitive touchpad module includes an oscillation circuit for generating an excitation signal, a power circuit connected to the oscillation circuit for providing a supply voltage for the oscillation circuit, and a tip connected to the oscillation circuit for emitting the excitation signal to apply to a trace of the capacitive touchpad module near a touch point when the electronic stylus touches the capacitive touchpad module, so as to change a waveform of a charging/discharging signal in the trace.
According to the present invention, an electronic stylus for touch input to a capacitive touchpad module includes an input terminal connected to the capacitive touchpad module via a signal line for receiving an excitation signal from the capacitive touchpad module, and a tip connected to the input terminal for emitting the excitation signal to apply to a trace of the capacitive touchpad module near a touch point when the electronic stylus touches the capacitive touchpad module, so as to change a waveform of a charging/discharging signal in the trace.
According to the present invention, an electronic stylus for touch input to a capacitive touchpad module includes a down-converter circuit for down-converting a signal transmitted from the capacitive touchpad module to generate an excitation signal, and a tip connected to the down-converter circuit for emitting the excitation signal to apply to a trace of the capacitive touchpad module near a touch point when the electronic stylus touches the capacitive touchpad module, so as to change a waveform of a charging/discharging signal in the trace.
According to the present invention, an electronic stylus for touch input to a capacitive touchpad module includes a demodulation circuit for demodulating a carrier transmitted from the capacitive touchpad module to generate an excitation signal, and a tip connected to the demodulation circuit for emitting the excitation signal to apply to a trace of the capacitive touchpad module near a touch point when the electronic stylus touches the capacitive touchpad module, so as to change a waveform of a charging/discharging signal in the trace.
According to the present invention, a method for an electronic stylus for touch input to a capacitive touchpad module includes applying the excitation signal to a tip of the electronic stylus, and emitting the excitation signal from the tip to apply to a trace of the capacitive touchpad module near a touch point when the electronic stylus touches the capacitive touchpad module, so as to change a waveform of a charging/discharging signal in the trace.
According to the present invention, a capacitive touchpad module includes an output terminal, a trace, and a detection circuit connected to the trace for detecting a charging/discharging signal from the trace to generate an excitation signal, which is related to a phase and a frequency of the charging/discharging signal, to transmit to an electronic stylus via the output terminal.
According to the present invention, a control method for a capacitive touchpad module includes detecting a charging/discharging signal from a trace of the capacitive touchpad module, and generating an excitation signal, which is related to a phase and a frequency of the charging/discharging signal, for transmitting to an electronic stylus.
According to the present invention, a capacitive touchpad module includes a trace, a detection circuit connected to the trace for detecting a charging/discharging signal from the trace to generate a detection signal which is related to a frequency and a phase of the charging/discharging signal, an up-converter circuit connected to the detection circuit for up-converting the detection signal to generate a high-frequency signal, a transceiver system connected to the up-converter circuit for transmitting the high-frequency signal to an electronic stylus.
According to the present invention, a control method for a capacitive touchpad module includes detecting a charging/discharging signal from a trace of the capacitive touchpad module for generating a detection signal which is related to a frequency and a phase of the charging/discharging signal, up-converting the detection signal for generating a high-frequency signal, and transmitting the high-frequency signal to an electronic stylus.
According to the present invention, a capacitive touchpad module includes: a trace, a detection circuit connected to the trace for detecting a charging/discharging signal from the trace to generate a detection signal which is related to a frequency and a phase of the charging/discharging signal, a modulation circuit connected to the detection circuit for generating a carrier according to the detection signal, and a transceiver system connected to the modulation circuit for transmitting the carrier to an electronic stylus.
According to the present invention, a control method for a capacitive touchpad module includes detecting a charging/discharging signal from a trace of the capacitive touchpad module for generating a detection signal which is related to a frequency and a phase of the charging/discharging signal, modulating the detection signal for generating a carrier, and transmitting the carrier to an electronic stylus.
According to the present invention, a control method for a capacitive touchpad module includes detecting a charging/discharging signal from a trace of the capacitive touchpad module for generating a detection signal which is related to a frequency and a phase of the charging/discharging signal, embedding data into a carrier according to the detection signal, and transmitting the carrier to an electronic stylus.
According to the present invention, a control method for a capacitive touchpad module includes detecting a charging/discharging signal from a trace of the capacitive touchpad module, and determining either a finger or an electronic stylus touching the capacitive touchpad module, depending on an increase or a decrease of an analog-to-digital conversion value of the charging/discharging signal.
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 according to the present invention taken in conjunction with the accompanying drawings, in which:
For capacitive touch input, as shown in
The phase difference may be zero. The tip 30 may be a metal, a flexible conductor, or a metal wrapped by a nonconductor. A metal 36 is around the tip 30 for use as a shielding layer to prevent electromagnetic interference (EMI). Between the tip 30 and the metal 36 is disposed an isolating insulator 39, and an insulator 31 wraps around the metal 36 to shield against ambient interference.
In the embodiment shown in
Projected capacitance touchpad modules may be classified into types of self-capacitance and mutual capacitance.
In
In
On the contrary, as shown in
The above description is not intended to limit any relationship between the charging/discharging signal and the ADC value. In other embodiments, depending on different signal processing procedures, it might also be possible that the corresponding ADC value is increased when the voltage amplitude of the charging/discharging signal experiences an increase or is decreased when the voltage amplitude of the charging/discharging signal experiences a decrease.
The phase relationship between an excitation signal Srf and a charging/discharging signal may be adjusted. For example, the waveform 144 shown in
Although a triangular waveform is taken as an example for the charging/discharging signal as shown in
As can be seen in
The intensity of the excitation signal Srf emitted by the electronic stylus 12 is adjusted to be a suitable level. If its intensity were set too high, the electronic stylus 12 would be detected when it actually has not touched the capacitive touchpad module 14 yet; on the contrary, if its intensity is set too low, the electronic stylus 12 would fail to be detected even when it touches on the capacitive touchpad module 14. The intensity of the excitation signal Srf may be adjusted by adjusting a peak voltage and a duty ratio of the excitation signal Srf.
While the present invention has been described in conjunction with preferred embodiment 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.
Claims
1. A control method for an apparatus including an electronic stylus and a capacitive touchpad module for touch input, the control method comprising the steps of:
- (A) generating an excitation signal having a constant phase difference from a charging/discharging signal in a trace of the capacitive touchpad module;
- (B) supplying the excitation signal to a tip of the electronic stylus;
- (C) emitting the excitation signal by the tip to apply to the trace of the capacitive touchpad module near a touch point when the tip touches the capacitive touchpad module, so as to change a waveform of the charging/discharging signal in the trace; and
- (D) sensing the touch point according to an amplitude of the waveform.
2. The control method of claim 1, wherein the step A comprises the step of setting a frequency of the excitation signal equal to an integral multiple of a frequency of the charging/discharging signal.
3. The control method of claim 1, wherein the step A comprises the step of setting a frequency of the excitation signal equal to a frequency of the charging/discharging signal and a duty ratio of the excitation signal equal to 50%.
4. The control method of claim 1, wherein the step A comprises the step of operating an oscillation circuit to generate the excitation signal.
5. The control method of claim 1, wherein the step A comprises the steps of:
- detecting the charging/discharging signal from the trace to generate a detection signal;
- up-converting the detection signal to generate a high-frequency signal;
- transmitting the high-frequency signal to the electronic stylus; and
- receiving and down-converting the high-frequency signal to generate the excitation signal.
6. The control method of claim 1, wherein the step A comprises the steps of:
- detecting the charging/discharging signal from the trace to generate a detection signal;
- modulating the detection signal to generate a modulated carrier signal;
- transmitting the modulated carrier signal to the electronic stylus; and
- receiving and demodulating the modulated carrier signal to generate the excitation signal.
7. The control method of claim 1, wherein the step B comprises the steps of:
- detecting the charging/discharging signal from the trace to generate a detection signal which is related to a phase and a frequency of the charging/discharging signal;
- embedding data representing the detection signal into a carrier signal;
- transmitting the carrier signal to the electronic stylus;
- extracting the data from the carrier signal; and
- generating the excitation signal according to the extracted data.
8. An electronic stylus for touch input to a capacitive touchpad module, comprising:
- an oscillation circuit generating an excitation signal having a constant phase difference from the charging/discharging signal;
- a power circuit connected to the oscillation circuit, providing a supply voltage for the oscillation circuit; and
- a tip connected to the oscillation circuit, emitting the excitation signal to apply to a trace of the capacitive touchpad module near a touch point when the electronic stylus touches the capacitive touchpad module, so as to change a waveform of a charging/discharging signal in the trace.
9. The electronic stylus of claim 8, wherein the oscillation circuit comprises:
- a boost circuit connected to the power circuit, boosting the supply voltage to generate a boosted voltage; and
- a quartz oscillator connected to the boost circuit, driven by the boosted voltage to generate the excitation signal.
10. The electronic stylus of claim 8, wherein the power circuit generates the supply voltage according to a radio frequency signal transmitted from the capacitive touchpad module.
11. The electronic stylus of claim 8, wherein the power circuit transforms a magnetic force into the supply voltage.
12. The electronic stylus of claim 8, wherein the power circuit comprises a battery providing the supply voltage.
13. The electronic stylus of claim 8, further comprising a switch being turned on or off to control whether or not to emit the excitation signal.
14. The electronic stylus of claim 8, wherein the tip comprises a metal.
15. The electronic stylus of claim 8, wherein the tip comprises a flexible conductor.
16. The electronic stylus of claim 8, wherein the tip comprises a metal wrapped by a nonconductor.
17. The electronic stylus of claim 8, further comprising:
- a metal wrapping around the tip;
- a first insulator wrapping around the metal for shielding against ambient interference; and
- a second insulator between the tip and the metal for separating the tip from the metal.
18. The electronic stylus of claim 8, wherein the excitation signal has a frequency equal to an integral multiple of a frequency of the charging/discharging signal.
19. The electronic stylus of claim 8, wherein the excitation signal has a frequency equal to a frequency of the charging/discharging signal and a duty ratio of 50%.
Type: Application
Filed: Sep 9, 2013
Publication Date: Feb 6, 2014
Applicant: Elan Microelectronic Corporation (Hsinchu)
Inventors: I-Hau YEH (Taipei City), Chi-Tein YEH (Chiayi City), Tsun-Min WANG (Miaoli County), Chun-Chung HUANG (Hsinchu City), Chung-Han CHENG (Kaohsiung City), Hung-Ming HUANG (Sanchong City)
Application Number: 14/021,676
International Classification: G06F 3/0354 (20060101); G06F 3/044 (20060101);