JP2000099255A - Coordinate detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the coordinate detecting device which can prevent coordinates from being concentrated on the center of a digitizer and can perform more accurate coordinate detection even in the case of low writing pressure, fast writing or a digitizer with a high load setting. SOLUTION: When a pen-down action is decided (S11), processes (S12, S14), wherein a predetermined resistance film is grounded right before potentials for X coordinate and Y coordinate are detected, and processes (S16, S18), wherein the predetermined resistance film is connected to Vcc right before the potentials for X coordinate Y coordinate are detected, are repeated by turns. When variation of a detected potential is large, its coordinates are excluded as unstable pen-down.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coordinate detecting device for detecting coordinates of a digitizer.

[0002]

2. Description of the Related Art In recent years, many small, portable information processing apparatuses that are lightweight and portable have been commercialized, and products that perform handwriting input and icon operations using a pen have been increasing. Regardless of the type of pen used, the resistive film pressure-sensitive digitizer is widely used because it can be realized with an inexpensive and simple configuration.

Here, the structure of a resistive film pressure-sensitive digitizer is shown. As shown in FIG. 12, the resistive film pressure-sensitive digitizer is composed of two upper and lower panels 30 made of a resin film or the like.
1 are arranged to face each other, and a sandwich-like structure is formed in which a resistive film 302 as a conductive sheet is formed inside the panel 301 by vapor deposition or the like. Here, an insulating spacer 303 is provided so that the two conductive sheets 302 do not come into contact with each other in a state where they are not pressed. Further, electrodes are provided at both ends of each of the resistance films, A lead wire is connected to each electrode and used as a terminal for applying a voltage or detecting a voltage. The directions in which the electrodes of each resistance film are arranged are arranged so as to be orthogonal to each other in the two resistance films. One of the two resistive films is used for detecting the X coordinate, and the other is used for detecting the Y coordinate. That is, in the resistive film for X coordinate detection, electrodes are provided on both left and right ends, while in the resistive film for Y coordinate detection, electrodes are provided on both upper and lower ends.

A part of the configuration of the conventional coordinate detecting device is configured as shown in FIG. 2 and operates as follows. That is, as shown in FIG. 13, it is detected whether or not the pen is down at a predetermined sampling period after the idle state (S100) (S101). This pen down detection is performed based on whether a pen down signal is detected. That is, as shown in “when pen down is detected” in FIG. 14, the switches in the configuration of FIG.
0 for a side, SW1 for b side, SW2 for b side, SW3 for a
Switch SW4 to the b side. Then, if there is a pen down, the output voltage of the pen down signal drops, so it is determined whether or not the pen down has occurred by looking at this.

Next, when it is determined that the pen is down, a voltage value is detected on the resistance film for detecting the X coordinate (S102). In this case, as shown in “X coordinate detection” of FIG.
Side, SW1 a side, SW2 b side, SW3 b side, SW
4 is switched to the a side. Then, the X coordinate detecting resistive film X
At t, the current flows from Vcc to GND,
The voltage value at the pressed point is detected via SW2 or SW4.

Next, a voltage value is detected on the resistive film for detecting the Y coordinate (S103). In this case, as shown in “when the Y coordinate is detected” in FIG. 14, SW0 is set to the b side, SW1 is set to the b side, and SW2 is set to a
Side, SW3 is switched to a side, and SW4 is switched to b side. Then, since a current flows from Vcc to GND in the resistance film Yt for detecting a Y resistance film, the voltage value at the pressed point is detected via SW1 or SW3. Then, the X coordinate and the Y coordinate are calculated based on the detected voltage value (S104). If it is not determined in step S101 that the pen-down has occurred, the process proceeds to step S101.
Return to 100.

[0007]

However, when the writing pressure is low, the writing speed is high, or a digitizer with a high load setting is used, the coordinates concentrated at the center of the digitizer tend to be detected. . In other words, in the case of an unstable pen down, such as when the pen is determined to be pen down by the pen down signal but contact is incomplete in the middle, the detection potential at the halfway pen down tends to be almost at the center of both ends of the digitizer. In some cases, the detection result may be different from the actual handwriting, for example, the handwriting suddenly jumps to the center of the screen. Note that this tendency may appear on either the X coordinate or the Y coordinate, or may appear on both the X coordinate and the Y coordinate. Therefore, the present invention can prevent the detected coordinates from being concentrated at the center of the digitizer even at the time of low writing pressure or high-speed writing, or when using a digitizer with a high load setting, and more accurately detect the coordinates. It is an object of the present invention to provide a coordinate detecting device capable of performing the following.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and, first, a digitizer having a resistive film for detecting an X coordinate and a resistive film for detecting a Y coordinate. A pen-down detecting means for detecting pen-down to the digitizer, and a first electric signal detecting process when pen-down is detected by the pen-down detecting means. Wherein the first Y-coordinate detecting resistive film is connected to the ground.
Ground connection processing, X-coordinate electric signal detection processing performed immediately after the first ground connection processing, second ground connection processing for connecting the X-coordinate detection resistive film to ground, and second ground connection processing A first electrical signal detection process including a Y-coordinate electrical signal detection process performed immediately after
A first power supply connection process for connecting the Y-coordinate detection resistance film to a predetermined power supply, a detection process for an X-coordinate electric signal performed immediately after the first power supply connection process,
A second electric signal detection process including a second power connection process for connecting the X-coordinate detection resistive film to a predetermined power source, and a Y-coordinate electric signal detection process performed immediately after the second power connection process; And an electric signal detection processing means for performing the first electric signal detection processing and the second electric signal detection processing at least once each. In the first configuration, in the first electric signal detection process, a process of connecting to the ground is performed immediately before the detection of the electric signal.
When the X-coordinate detecting resistive film and the Y-coordinate detecting resistive film are not in contact with each other, the detected electric signal is at the ground level, and when the pen is unstable, the ground level or a potential close thereto is detected. It will be easier. On the other hand, in the second electric signal detection process, a process of connecting to a predetermined power supply is performed immediately before the detection of the electric signal. Therefore, when the resistance film for X coordinate detection and the resistance film for Y coordinate detection are not In the meantime, the detected electric signal becomes the level of the power supply, and if the pen is unstable, the level of the power supply or a potential close thereto is easily detected. Therefore, by detecting the fluctuation of the detected electric signal and excluding it as an unstable pen-down when the fluctuation cannot be obtained at a normal human writing speed, the coordinates are concentrated at the center in the case of the unstable pen-down. The phenomenon can be prevented, and coordinate detection faithful to handwriting can be performed.

Secondly, in the first configuration, the electric signal detection processing means alternately performs the first electric signal detection processing and the second electric signal detection processing. . Thereby, the unstable pen down can be detected by comparing the electric signals in the first electric signal detection processing and the second electric signal detection processing which are temporally adjacent to each other, and detecting the fluctuation.

Third, in the first or second configuration, the coordinate detecting device may further include an electric signal detected by the first electric signal detecting process,
Unstable pen down detecting means for detecting an unstable pen down based on a difference from the electric signal detected by the electric signal detecting processing, and coordinate calculating means for calculating coordinates based on the electric signal detected by the electric signal detecting processing means And a coordinate calculation means for stopping the calculation of coordinates when the unstable pen down detection means detects an unstable pen down. Therefore, when an unstable pen down is detected, the coordinate calculation unit stops calculating the coordinates, so that a phenomenon in which the coordinates are concentrated at the center in the case of the unstable pen down can be prevented, and the coordinates faithful to the handwriting can be prevented. Detection can be performed.

Fourth, in the above-mentioned second configuration, the coordinate detecting device may further comprise: if a fluctuation amount of the electric signal detected by the electric signal detecting means is larger than a predetermined amount, Unstable pen down detection means for detecting an unstable pen down; and coordinate calculation means for calculating coordinates based on the electric signal detected by the electric signal detection processing means, wherein the unstable pen down detection means detects an unstable pen down. And a coordinate calculating means for stopping the calculation of the coordinates when the calculation is performed. Therefore, when an unstable pen down is detected, the coordinate calculation unit stops calculating the coordinates, so that a phenomenon in which the coordinates are concentrated at the center in the case of the unstable pen down can be prevented, and the coordinates faithful to the handwriting can be prevented. Detection can be performed.

Fifth, in any one of the first to fourth configurations, the total number of processing times of the first electrical signal detection processing and the second electrical signal detection processing is performed. Is at least three times.
Thereby, the fluctuation of the electric signal can be detected in more detail. Sixth, in any of the first to fifth configurations, the total number of times of the first electrical signal detection process and the number of second electrical signal detection processes is three. And the difference between the electric signal detected by the first electric signal detection processing and the electric signal detected by the second electric signal detection processing, and the electric power detected by the second electric signal detection processing. From the difference between the signal and the electric signal detected by the third electric signal detection process,
It is characterized in that the amount of change in the electric signal is determined.

A seventh feature is that, in any one of the first to sixth configurations, the pen-down detection is performed at a predetermined sampling cycle. Eighthly, in any one of the first to seventh configurations, the electric signal is an electric signal of a potential.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, a coordinate detection device A according to the present invention
0, a switch circuit 12, an A / D converter 14, an operation control unit 16, a pen-down detection unit 18, a sampling cycle counter 20, and a host CPU 22.

The digitizer 10 is a pressure-sensitive coordinate detection sensor having a resistive film Xt for detecting X coordinates and a resistive film Yt for detecting Y coordinates. When the digitizer is pressed by a pen or a finger, An electric signal corresponding to the pressed position is output. The switch circuit 12 has switches SW0, SW1, SW2, SW3, and SW4 as shown in FIG. That is, the switch SW0 switches the connection between the X-coordinate detection resistive film Xt and the pen-down detecting constant voltage Vcc, and the switch SW1 switches the constant voltage Vcc and A with respect to one electrode of the X-coordinate detecting resistive film Xt. The switch SW2 switches between the constant voltage Vcc and A / D for one electrode of the Y-coordinate detection resistive film Yt.
The switching between the converters 14 is performed.
Switches between the ground (Gnd) and the A / D converter 14 for the other electrode of the X-coordinate detection resistive film Xt,
The switch SW4 switches between the ground (Gnd) and the A / D converter 14 for the other electrode of the Y-coordinate detection resistive film Yt. The switching control of each switch is performed by the arithmetic control unit 16. The constant voltage Vcc functions as the predetermined power supply.

Next, the A / D converter 14 converts a voltage value as an electric signal detected from the digitizer 10 from analog data to digital data. The arithmetic control unit 16 performs various controls for coordinate detection. The arithmetic control unit 16 controls the sampling period counter 20, the switch circuit 12, the A /
It controls the D-converter 14, performs arithmetic processing for coordinate calculation, correction processing, noise processing, and the like. Particularly, in the present embodiment, when detecting the X coordinate and the Y coordinate, immediately before that, the process of switching the predetermined resistance film to the ground (Gnd) side and the process of switching to the constant voltage Vcc side are alternately performed. The switching of each switch is controlled. Details will be described later.

A pen-down detecting section 18 as a pen-down detecting means detects whether or not a pen-down has occurred, and detects a pen-down signal when the switch circuit 12 is switched to a pen-down detecting switch state. I do. Also, a sampling period counter 2
0 generates a periodic sampling time. The arithmetic control unit 16, the switch circuit 12, and the A / D converter 1
Reference numeral 4 functions as the electric signal detection processing means. Further, the host CPU 22 interprets the coordinate data generated by the arithmetic control unit 16 and performs processing such as drawing on a display device and character recognition processing.

The operation of the coordinate detecting device A having the above configuration will be described with reference to FIG. First, after the idle state (S10), it is detected whether or not the pen is down at a predetermined sampling cycle (S11). This pen down detection is performed based on whether a pen down signal is detected. That is, as shown in “when pen down is detected” in FIG. 4, each switch in the configuration of FIG.
On the a side, switch SW1 on the b side, switch SW2 on the b side
Side, switch SW3 is switched to a side, and switch SW4 is switched to b side. Then, if there is a pen down,
Since the current flows on the ground (GND) side of the Y-coordinate detection resistance film Yt, the output voltage of the pen-down signal drops. Here, when it is not determined that the pen-down has occurred, the process returns to step S10.

On the other hand, if it is determined that the pen has been down, first, the first potential detection is performed. That is, the pen down signal is sent from the pen down detection unit 18 to the operation control unit 1.
6 and it is determined that the pen has been down, the arithmetic control unit 16 controls the switch circuit 12 to perform the following processing.

First, a process of connecting the resistance film Yt for Y coordinate detection to the ground (GND) side is performed (S12). That is, the switch SW0 is switched to the b-side, the switch SW1 is switched to the b-side, the switch SW2 is switched to the b-side, the switch SW3 is switched to the a-side, and the switch SW4 is switched to the b-side. The switch is switched as shown in FIG. The time for connecting to the ground is extremely short.

Immediately thereafter, the X-coordinate detecting resistive film X
The potential at the pressing point t is detected (S13). That is, an electric signal is detected in the form of a potential. The detected potential is X
It becomes a potential for coordinates. That is, as compared with the switch switching state in the case of step S12, the switch SW1 is
When the switch SW3 is switched to the b side and the switch SW4 is switched to the a side, the state of “when the X coordinate is detected” in FIG.
To the switch switching state shown in (1). Then, in the X-coordinate detection resistive film Xt, the constant voltage Vcc and the ground (Gn)
Since the current is supplied during the period d), the potential of the pressed point on the X-coordinate detection resistive film Xt is detected via the switch SW2 or the switch SW4. The detected potential is supplied to the A / D converter 14
, And is sent to the arithmetic and control unit 16.

Next, a process for connecting the X coordinate detecting resistance film Xt to the ground (Gnd) side is performed (S14). That is, the switch SW1 is switched to the b side as compared with the switch switching state in the case of the above step S13, and the state of "X resistance film Gnd connection" in FIG. 4, that is, the switch switching state shown in FIG.

Immediately after that, the Y-coordinate detecting resistive film Y
The potential at the pressed point at t is detected (S15). This detected potential becomes the potential for the Y coordinate. That is, the switch SW2 is set to the a side, the switch SW3 is set to the a side, and the switch SW
4 is switched to the b side, and the state at the time of "Y coordinate detection" in FIG. 4, that is, the switch switching state shown in FIG. Then, a current is applied between the constant voltage Vcc and the ground (GND) in the Y-coordinate detection resistance film Yt, so that the potential at the pressing point of the Y-coordinate detection resistance film Yt is detected via the switch SW1 or the switch SW3. The detected potential is similarly converted into digital data by the A / D converter 14 and sent to the arithmetic and control unit 16. The first potential detection is performed as described above. Steps S12 to S15
The processing up to corresponds to the first electric signal detection processing.

Next, a second potential detection is performed. In the first potential detection, each resistive film was switched to the ground (Gnd) side, but this time, each resistive film was switched to a constant voltage (Vcc).
Is performed. That is, the arithmetic control unit 16 controls the switch circuit 12 to perform the following processing.

First, a process for switching the resistance film Yt for Y coordinate detection to the constant voltage (Vcc) side is performed (S16). That is, the switch SW4 is switched to the "a" side as compared with the switch switching state in the case of step S15, and the state of "connection of the Y resistance film Vcc" in FIG. 4, that is, the switch switching state shown in FIG.

Then, the potential of the pressed point on the X-coordinate detecting resistive film Xt is detected (S17). The detected potential is X
It becomes a potential for coordinates. That is, as compared with the switch switching state in the case of step S16, the switch SW1 is
When the switch SW2 is switched to the b side and the switch SW3 is switched to the b side, the state at the time of “X coordinate detection” in FIG.
To the switch switching state shown in (1). Then, in the X-coordinate detection resistive film Xt, the constant voltage Vcc and the ground (Gn)
Since the current is supplied during the period d), the potential of the pressed point on the X-coordinate detection resistive film Xt is detected via the switch SW2 or the switch SW4. The detected potential is supplied to the A / D converter 14
, And is sent to the arithmetic and control unit 16.

Next, a process for switching the X-coordinate detection resistance film Xt to the constant voltage (Vcc) side is performed (S18). That is, the switch SW3 is switched to the a side as compared with the switch switching state in the case of the step S17, and the state of "X resistance film Vcc connection" in FIG. 4, that is, the switch switching state shown in FIG.

Then, the potential of the pressed point on the resistive film Yt for Y coordinate detection is detected (S19). This detected potential becomes the potential for the Y coordinate. That is, the above step S1
8 compared to the switch switching state in the case of
1 for b side, switch SW2 for a side, switch SW4 for b
To the state of “when the Y coordinate is detected” in FIG. 4, that is, the switch switching state shown in FIG. Then, a current is applied between the constant voltage Vcc and the ground (GND) in the Y-coordinate detection resistance film Yt.
Detect via W3. The detected potential is similarly converted into digital data by the A / D converter 14 and sent to the arithmetic and control unit 16. The second potential detection is performed as described above. The processing of steps S16 to S19 corresponds to the second electric signal detection processing.

Next, a third potential detection is performed. The third potential detection is performed in the same manner as the first potential detection. That is, first, the resistance film Yt for Y coordinate detection is grounded (G
The processing for switching to the nd) side is performed (S20). That is,
Compared with the switch switching state in the case of step S18, the switch SW2 is switched to the b side to be in the state of "connection of the Y resistance film Gnd" in FIG. 4, that is, the switch switching state shown in FIG. Then, the potential of the pressed point on the X-coordinate detection resistive film Xt is detected (S21). The manner of detection is the same as in step S13.

Next, a process for switching the X-coordinate detection resistive film Xt to the ground (Gnd) side is performed (S22). That is, as in step S14, the switch SW1 is set to b
To the state of "X resistance film Gnd connection" in FIG. 4, that is, the switch switching state shown in FIG.
Then, the potential of the pressed point on the Y-coordinate detection resistance film Yt is detected (S23). The method of detection is as described in step S
This is the same as the case of No. 15. The third potential detection is performed as described above. The processing of steps S20 to S23 corresponds to the first electric signal detection processing.

Next, it is determined whether the pen down is an unstable pen down (S24). That is, the potentials detected by the potential detection in each time are compared, and when the fluctuation is large, it is determined that the pen is unstable. That is, if there is a large fluctuation, it is determined that the pen is unstable because the fluctuation cannot be obtained at the normal human writing speed. The determination of the unstable pen down is performed by the arithmetic control unit 1.
6 does. That is, the arithmetic control unit 16 functions as the unstable pen down detecting means.

For example, the difference between the potential detected at the first time and the potential detected at the second time is calculated, and the difference between the potential detected at the second time and the potential detected at the third time is calculated. If the difference is large by taking the difference between the two differences, it is determined that the pen is unstable. That is, assuming that the potential detected at the first time is a, the potential detected at the second time is b, and the potential detected at the third time is c, ba-c
-B, and (c−b) − (ba) = c−
2b + a is calculated. Then, when a, b, and c are substantially equal, the value is close to zero. Since this determination is made for each of the X coordinate and the Y coordinate, if any of them is determined to be unstable, it is determined that the pen is unstable. If both or any of the two differences exceeds a certain threshold value, an unstable pen down may be determined.

If it is determined in step S24 that the pen is unstable, a predetermined process such as invalidating the coordinates or determining that the pen is up is performed (S2).
6). On the other hand, if it is not determined that the pen is unstable, the coordinates are calculated based on the detected potential (S25). That is, the arithmetic control unit 16 functions as the coordinate calculation unit.

FIG. 11 is a time chart showing the steps of the above processing. Here, S0, S1, S2, and S3 in FIG. 11 indicate timing based on the sampling cycle, and X01, X1 between S0 and S1.
02 and X03 indicate potentials detected during the first, second, and third X-coordinate detection, respectively, and S0-S
Y01, Y02, and Y03 in the interval 1 indicate potentials detected during the first, second, and third Y coordinate detections, respectively. Note that each of the periods S0, S1, S2, and S3 is a coordinate detection period.

That is, focusing on the applied / detected potential of the switch SW2, immediately before the timing of S0, the resistance film for detecting the Y coordinate is connected to the ground (Gnd) as in step S12, so is there.
However, actually, the Y-coordinate detection resistive film is connected to the ground (Gnd) for a predetermined time before the timing of S0. Thereafter, in X01, in step S13
As described above, the switch SW2 is switched to the b side and the potential for the X coordinate is detected, so that the potential in the period of X01 is the value detected from the switch SW2. The X-coordinate detection resistive film is connected to the ground (Gnd) as shown in step S14.
2 remains switched to the b side. Then, Y01
In the period, the detection of the potential for the Y coordinate (step S
15). At this time, the switch SW2 is connected to the constant voltage Vcc, so that the potential during that period becomes Vcc.

Next, as shown in step S16,
Since the resistance film for detecting the Y coordinate is connected to Vcc, the potential of the switch SW2 at that time becomes Vcc. Thereafter, in the period of X02, as shown in step S17, the switch SW2 is switched to the b side and the potential for the X coordinate is detected, so the potential in the period of X1 is the value detected from the switch SW2. . The X-coordinate detection resistive film is connected to the constant voltage Vcc as shown in step S18, but at this time, the switch SW2 remains switched to the side b. Thereafter, during the period of Y02, the detection of the potential for the Y coordinate (Step S19) is performed. However, since the switch SW2 is connected to the constant voltage Vcc, the potential during that period becomes Vcc.

Next, as shown in step S20,
Since the Y-coordinate detecting resistance film is connected to the ground (Gnd), the potential of the switch SW2 at that time becomes the Gnd level. Thereafter, in the period of X03, the switch SW2 is switched to the b side and the potential for the X coordinate is detected as in step S21, so the potential in the period of X03 is the value detected from the switch SW2. . Note that X
The resistive film for coordinate detection is connected to the ground as shown in step S22.
Side remains switched. Thereafter, during the period of Y03, the detection of the Y coordinate is performed (step S23). At this time, the switch SW2 is connected to the constant voltage Vcc, so that the potential during that period is Vcc.

Next, focusing on the applied / detected potential of the switch SW1, immediately before the timing of S0, the resistance film for detecting the Y coordinate is grounded (Gn) as in step S12.
d), in which case the switch SW1 is set to b
And the switch SW3 is on the b side, and the switch SW1 detects the Gnd level. However, actually, a predetermined time before the timing of S0 is the switch SW.
1 is at the Gnd level. Then X
In the period of 01, the detection of the potential for the X coordinate (step S13) is performed.
Is connected to Vcc, the potential during that period is Vcc
Becomes

Next, as shown in step S14,
Since the X-coordinate detection resistance film is connected to the ground (Gnd), the potential of the switch SW1 at that time becomes the ground level. Thereafter, in the period of Y01, as shown in step S15, the switch SW3 is switched to the a side and the potential for the Y coordinate is detected, so the potential in the period of Y01 is the value detected from the switch SW1. . The resistance film for detecting the Y coordinate is connected to the constant voltage Vcc as shown in step S16.
W1 remains switched to the b side. Then, X0
In the period 2, the detection of the potential for the X coordinate is performed (step S17). At this time, the switch SW1 is connected to Vcc, and the potential during that period is Vcc.

Next, as shown in step S18,
Since the X-coordinate detection resistive film is connected to Vcc, the potential of the switch SW2 at that time becomes Vcc. Thereafter, in the period of Y02, as shown in step S19, the switch SW1 is switched to the b side and the potential for the Y coordinate is detected, so the potential in the period of Y02 is the value detected from the switch SW1. . The resistive film for Y coordinate detection is connected to the ground (Gnd) as shown in step S20, but at this time, the switch SW1 is still switched to the b side. Then, in the period of X03,
The potential for the X coordinate is detected (step S21). At this time, since the switch SW1 is connected to Vcc, the potential during that period is Vcc.

Next, as shown in step S22,
Since the X-coordinate detection resistance film is connected to the ground (Gnd), the potential of the switch SW1 at that time becomes the ground level. Thereafter, in the period of Y03, as shown in step S23, the switch SW3 is switched to the a side and the potential for the Y coordinate is detected, so that the potential in the period of Y03 is the value detected from the switch SW1. .

In step S10, pen down detection is performed, which is determined by a pen down signal immediately before each coordinate detection period. For example, in the coordinate detection period between S0 and S1, the determination is made based on the pen down signal immediately before S0, and when the pen down signal is equal to or less than a predetermined value, it is determined that the pen is down. That is, S1-S
In the coordinate detection period between S2 and S2 and the coordinate detection period between S2 and S3, the immediately preceding pen-down signal has not completely dropped, but this is because the pen-down was originally unstable. Since it has become equal to or less than the value, it means that it is determined in step S10 that the pen has been down.

Here, when the pen down is stably performed on the digitizer 10, the potential corresponding to the pressed point is accurately detected. However, when the pen down is unstable, the following is performed. become. That is, the ground (G
nd), the charges accumulated in the resistive film are released. Therefore, when the X-coordinate detecting resistive film Xt and the Y-coordinate detecting resistive film Yt are not in contact with each other, the ground level That is, if the resistance film Xt for detecting the X coordinate and the resistance film Yt for detecting the Y coordinate are in contact with each other, the potential at that time is detected. It should be at the ground level, and if the pen is unstable, the ground level or a potential close to the ground level is easily detected. On the other hand, if the X-coordinate detection resistive film Xt and the Y-coordinate detective resistive film Yt are not in contact with each other, electric charges are accumulated in the resistive film when connected to the constant voltage Vcc immediately before. Will be detected.
That is, if the X-coordinate detecting resistive film Xt and the Y-coordinate detecting resistive film Yt are in contact with each other, the potential at that time is detected, but if not, they should be at the Vcc level. In the case of a stable pen down, the Vcc level or a potential close thereto is easily detected.

Then, as a process immediately before detecting the potential, a process of connecting to the ground (Gnd) and a process of connecting to Vcc are performed alternately. Since the difference between the detected potential and the potential detected for the second time is large and the difference between the potential detected for the second time and the potential detected for the third time is likely to be large, the pen down in this case is unstable pen down. Is easy to determine. Therefore, as a result, by invalidating the coordinates or determining that the pen is up, it is possible to prevent the detection of the coordinates concentrated at the center by detecting the coordinates at the intermediate position as in the related art. Further, in the present embodiment, in step S11, not only the pen down is determined, but also it is determined whether the pen is down and whether it is not an unstable pen down more reliably by detecting a temporal change in the detected potential thereafter. be able to.

For example, FIG. 11 shows an example in which the potential cannot be properly detected during the first detection and the second detection during the period between S1 and S2. That is, in the first detection of the potential, since the connection to the ground is made immediately before, in the case of the unstable pen down, the potential detected during the period of X11 and Y11 is the ground level or a level close thereto. On the other hand, in the second detection of the potential, since it is connected to the constant voltage Vcc immediately before, in the case of unstable pen down, the potential detected during the period of X12 and Y12 is Vcc.
Or a level close to this. Then, since the difference between the first and second potentials becomes large, it is easy to determine that the pen is unstable. Note that it is assumed that the potential has been properly detected during the periods X13 and Y13.

FIG. 11 shows an example in which the potential cannot be properly detected in the first, second, and third times in the period from S2 to S3. In other words, in the first and third potential detections, since the ground is connected immediately before, in the case of an unstable pen down, X21, Y
The potentials detected during the periods 21, 21, and 23 are at or near the ground level. On the other hand, in the second detection of the potential, since it is connected to the constant voltage Vcc immediately before, in the case of an unstable pen down, the potential detected during the period of X22 and Y22 is at the Vcc level or a level close thereto.

In the same detection, the ground level or the Vcc level may be detected without detecting the potential for the Y coordinate but detecting the potential for the X coordinate. For example, in the same first detection in the above case, a potential corresponding to the pressed point is detected for the potential for the X coordinate, but a ground level may be detected for the potential for the Y coordinate. sell.

In the above description, in the first and third potential detections, the connection to Gnd was made immediately before, and in the second potential detection, the connection to the constant voltage Vcc was described. However, the first and third times may be connected to the constant voltage Vcc, and the second time may be connected to the ground. In order to increase the fluctuation of the detection potential, the ground connection is performed. The first electric signal detection processing and the second electric signal detection processing for connection to a constant voltage may be performed alternately. Further, the process of connecting to the ground and the process of connecting to the constant voltage may be performed only once. That is, each of the first electric signal detection process and the second electric signal detection process may be performed only once. Further, in the above description, the total number of times of the first electrical signal detection process and the second electrical signal detection process has been described as three, but is not limited thereto and may be four or more. .

In the above description, the first electric signal detection processing and the second electric signal detection processing are performed alternately. However, the present invention is not limited to this. That is, for example, when the number of times of processing is three times, the first time and the second time
The first time is defined as a first electrical signal detection process, the third time is defined as a second electrical signal detection process, and the difference between the first detected potential and the third detected potential is calculated. The difference between the potential and the third detection potential may be calculated.

Further, the time for connecting to the ground or the time for connecting to Vcc immediately before detecting the potential may be arbitrarily set. That is, the connection time can be set by a command, so that the accuracy of fluctuation detection can be improved. However, in this case, it is preferable to allow the user to freely set the time because an influence such as a decrease in the sampling speed can be considered. In the above description, a 4-wire digitizer has been described. However, the present invention is not limited to this, and an 8-wire digitizer may be used.

Further, without performing the process of connecting to the ground side or the constant voltage Vcc side immediately before, detection of the potential for the X coordinate and Y potential
By detecting the potential for coordinates a plurality of times (for example, three times),
A method of determining whether or not an unstable pen down is considered from the change is also considered.In such a case, the coordinates of the intermediate position are more likely to be detected, and it is considered that the change is determined to be not so large. Therefore, it can not be said that the phenomenon that the coordinates are concentrated at the center position cannot be eliminated.

[0052]

According to the coordinate detecting device according to the present invention,
In the first electrical signal detection process, the process of connecting to the ground is performed immediately before the detection of the electrical signal. The generated electric signal is at the ground level, and if the pen is unstable, the ground level or a potential close to the ground level is easily detected. On the other hand, in the second electric signal detection process, a process of connecting to a predetermined power supply is performed immediately before the detection of the electric signal. Therefore, when the resistance film for X coordinate detection and the resistance film for Y coordinate detection are not In this case, the detected electric signal is at the level of the power supply, and if the pen is unstable, the ground level or a potential close to the ground level is easily detected. In the case of fluctuations that cannot be obtained with the writing speed of と し て, it is possible to prevent the phenomenon that coordinates are concentrated at the center in the case of unstable pen down by eliminating as unstable pen down, and perform coordinate detection faithful to handwriting be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a coordinate detection device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a digitizer and a switch circuit connected to the digitizer.

FIG. 3 is a flowchart illustrating an operation of the coordinate detection device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a switch switching state during each process.

FIG. 5 is a circuit diagram showing a switch switching state when a resistive film for Y coordinate detection is connected to ground.

FIG. 6 is a circuit diagram showing a switch switching state when an X coordinate detection resistive film is connected to ground.

FIG. 7 is a circuit diagram showing a switch switching state when a Y-coordinate detection resistive film is connected to Vcc.

FIG. 8 is a circuit diagram showing a switch switching state when an X coordinate detecting resistive film is connected to Vcc.

FIG. 9 is a circuit diagram showing a switch switching state at the time of detecting a potential for X coordinate detection.

FIG. 10 is a circuit diagram showing a switch switching state at the time of detecting a potential for detecting a Y coordinate.

FIG. 11 is a time chart for explaining the operation of the coordinate detection device according to the embodiment of the present invention.

FIG. 12 is a basic configuration diagram of a resistive film pressure-sensitive digitizer.

FIG. 13 is a flowchart showing the operation of a conventional coordinate detection device.

FIG. 14 is an explanatory diagram showing a switch switching state in each process of the conventional coordinate detection device.

[Explanation of symbols]

 A coordinate detection device 10 digitizer Xt X-coordinate detection resistive film Yt Y-coordinate detection resistive film 12 switch circuit 14 A / D converter 16 arithmetic control unit 18 pen-down detection unit 20 sampling cycle counter 22 host CPU

Claims (8)

[Claims] 1. A coordinate detecting device for detecting coordinates pressed by a digitizer having a resistive film for detecting an X coordinate and a resistive film for detecting a Y coordinate, a pen down detecting means for detecting pen down to the digitizer, A first electric signal detection process when the pen-down detection means detects that the pen is down, a first ground connection process for connecting a Y-coordinate detection resistive film to the ground; and a first ground connection process. X-coordinate electric signal detection processing performed immediately after the above, a second ground connection processing for connecting the X-coordinate detection resistive film to the ground, and Y-coordinate electric signal detection processing performed immediately after the second ground connection processing. A first electric signal detecting process including a detecting process, a second electric signal detecting process, a first power connecting process for connecting the Y coordinate detecting resistive film to a predetermined power source, and the first power connecting process. X-coordinate electrical signal detection processing performed immediately after the processing, second power connection processing for connecting the X-coordinate detection resistance film to a predetermined power supply, and Y-coordinate detection processing performed immediately after the second power connection processing. An electrical signal detection processing unit that performs a second electrical signal detection process having an electrical signal detection process, and performs the first electrical signal detection process and the second electrical signal detection process at least once each. A coordinate detection device characterized by the above-mentioned. 2. The coordinate detection apparatus according to claim 1, wherein said electric signal detection processing means performs the first electric signal detection processing and the second electric signal detection processing alternately. 3. The method according to claim 2, wherein the coordinate detecting device is further configured to be unstable based on a difference between the electric signal detected by the first electric signal detecting process and the electric signal detected by the second electric signal detecting process. Unstable pen down detection means for detecting pen down; and coordinate calculation means for calculating coordinates based on the electric signal detected by the electric signal detection processing means, wherein unstable pen down is detected by the unstable pen down detection means. 3. The coordinate detecting device according to claim 1, further comprising: a coordinate calculating unit that stops calculating the coordinates in the case. 4. An unstable pen down detecting means for detecting an unstable pen down when the variation of the electric signal detected by the electric signal detecting means is larger than a predetermined amount. A coordinate calculation means for calculating coordinates based on the electric signal detected by the electric signal detection processing means, wherein when the unstable pen down detection means detects an unstable pen down, the calculation of the coordinates is stopped. The coordinate detecting device according to claim 2, further comprising a coordinate calculating unit. 5. The total number of times of the first electrical signal detection process and the number of second electrical signal detection processes is at least three times. Or the coordinate detection device according to 4. 6. The total number of processing times of the first electric signal detection processing and the number of processing times of the second electric signal detection processing is three, and the electric number detected by the first electric signal detection processing is three. The difference between the signal and the electric signal detected by the second electric signal detection processing, the electric signal detected by the second electric signal detection processing, and the electric signal detected by the third electric signal detection processing 3. The amount of change in the electric signal is determined from the difference between
Or the coordinate detection device according to 3 or 4 or 5. 7. The method according to claim 1, wherein the detection of the pen down is performed at a predetermined sampling period.
Or the coordinate detection device according to 3 or 4 or 5 or 6. 8. The coordinate detecting device according to claim 1, wherein the electric signal is an electric signal of a potential.