JP2839972B2 - Pressure-sensitive coordinate input device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive coordinate input device used for a computer device such as an office automation (OA) device.

[0002]

2. Description of the Related Art FIG. 5 is a diagram for explaining an output operation of a pressure-sensitive tablet of a pressure-sensitive coordinate input device. In FIG. 1, reference numeral 1 denotes a resistance sheet for an X coordinate, and terminals XL and XH are attached to both left and right ends thereof. Also, 2
Is a resistance sheet for the Y coordinate, and terminals YL and YH are attached to both upper and lower ends thereof. Each terminal is connected to the output of the driver DXL, DXH, DYL, DYH, respectively, and by controlling these drivers, the terminal XL
And YL can be set to L level (for example, 0 volts) or open (floating), and terminals XH and YH can be set to H level (for example, 5 volts) or open.

Accordingly, the resistance sheets 1 can be set to a high impedance state by opening both the terminals XL and YL, or the resistance sheet can be given an inclined potential by setting the terminal XL to the L level and the terminal XH to the H level. Is also possible. This is the same for the resistance sheet 2.

The resistance sheets 1 and 2 are pressed by the input pen P and are in contact with each other at a point P. Rx1 is the resistance between the contact point Pi and the terminal XL, Rx2 is the contact point Pi
And the terminal XH. Similarly, Ry1 is the resistance value between the contact point Pi and the terminal YL, and Ry2 is the contact point P
It shows the resistance between i and the terminal YH.

When the drivers DXL and DXH are both turned on, the terminal XL is set to the L level and the terminal XH is set to the H level. On the other hand, when both the drivers DYL and DYH are turned off, the resistance sheet 2 is set to the high impedance state. If the voltage between the terminals XH and XL is Vc (for example, 5 V), the potential of the contact point Pi is Vc · Rx1 /
It is equal to (Rx1 + Rx2). This potential is converted from the terminal YL to an X-coordinate potential indicating the X-coordinate of the contact point by the A / D converter 1.
03 is output. Turn off the drivers DXL and DXH,
By turning on both the drivers DYL and DYH,
Similarly, from the terminal XL, the Y coordinate potential is set to the A / D converter 1
03 is output. The A / D converter 103 converts these potentials into digital values and supplies them to a CPU (Central Processing Unit).

[0006]

In the conventional pressure-sensitive coordinate input device using a resistance sheet as described above, when an input pen P presses a pressure-sensitive surface formed of a resistance sheet as shown in FIG. Hand or fingertip Q touches the pressure-sensitive surface (hereinafter,
In this case, the dividing resistance R of the sheet 1 is set between the contact point Pi by the pen P and the contact point Qi by the hand.
x3 'and the split resistor Ry3' of the sheet 2 are connected in parallel, so that the terminals XL and YH and the terminal XL
, XH becomes lower than the normal value when there is no touch, and the contact point Pi is detected as being at a position completely different from the actual position.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to provide a highly accurate pressure-sensitive coordinate input device which prevents erroneous input due to manual operation.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pressure-sensitive coordinate input device having a pressure-sensitive tablet constituted by a resistance sheet, and for determining the validity of read coordinate data. A table that stores the threshold value with an address individually assigned to each area of the pressure-sensitive surface, a threshold value at an address corresponding to the read coordinate data, and a pressing force of the pressure-sensitive surface output from the pressure-sensitive tablet. and means for comparing the check voltage corresponding, stored in the table
The threshold value for the central part of the pressure-sensitive tablet and the operator
Adjust the sensitivity of the near part by adjusting the left and right
It is set to be lower than the sensitivity of the part far from the author
This is achieved by a pressure-sensitive coordinate input device.

[0009]

The X coordinate and Y of the input point, that is, the pressed point of the input pen
When the coordinates are read, they are compared with threshold values with reference to a table to determine their validity. In this table, the threshold value is stored individually for each divided area of the pressure-sensitive surface, so that the sensitivity of the pressure-sensitive surface can be set freely over the entire surface. Close to center and operator
Sensitivity of the right and left ends and the part far from the operator.
Since the sensitivity is set lower than the sensitivity , erroneous input due to hand touch can be effectively prevented. In addition, the tablet has been enlarged
In this case, the variation in sensitivity can be easily corrected.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 3 is a block diagram of an embodiment of the pressure-sensitive coordinate input device according to the present invention. In the figure, 101 is a pressure-sensitive tablet, 102 is a driver circuit for driving the pressure-sensitive tablet, 103 is an A / D converter that converts a voltage signal output from the pressure-sensitive tablet 101 into a digital signal, 1
04 is a tablet voltage detection circuit for detecting whether or not the input pen is pressing the tablet, 106 is a ROM (read only memory) storing a control program of the device, and 107 is a device for storing various data during operation of the device. RAM (random access memory) for temporarily storing, 1
Reference numeral 05 denotes a CPU (central processing unit) for controlling the entire apparatus.

FIG. 4A is a timing chart for explaining the operation of the pressure-sensitive coordinate input device. In the figure, t indicates a section for detecting the position of the input pen, and one section includes a sampling period for reading the X coordinate and the Y coordinate of the pen a plurality of times (n times), and correction of the read coordinate data. And an averaging process cycle for executing the averaging process. FIG. 4B is an enlarged view of a part of FIG. 4A. As shown in this enlarged view, in the sampling period of each section, first, the check operation CF before the first coordinate reading is executed. Then, the reading operation x of the X coordinate is performed.
The read operation y of the Y coordinate and the check operation CM after the coordinate read which also serves as the check before the next coordinate read are repeatedly executed, and finally, the check operation CR after the final coordinate read is executed.

The contents of the check operation will be described with reference to FIG. First, before reading the coordinates, the voltage at the terminal YL is read from the A / D converter 103 as the check voltage VTAB with the driver DXH turned on and the other drivers DXL, DYH and DYL turned off. If the check voltage VTAB is higher than the predetermined voltage Va, coordinate reading is performed.
If the check voltage VTAB in the above state is higher than the threshold voltage VSH after reading the coordinates, the read coordinate data is valid. The threshold voltage VSH is
It is represented by Va (constant voltage value) + Vb (variable voltage value).
The threshold voltage VSH is the value of the read X-coordinate data and Y-coordinate data, that is, a value depending on the output of the A / D converter 103, and is stored in a predetermined table in advance. A
Since the output of the / D converter 103 is given to the table as an address, when an 8-bit A / D converter is used,
Up to 256 thresholds can be stored individually in a table, and when using a 10-bit A / D converter, up to 1024 thresholds can be stored individually in a table It is.

FIG. 2 shows an example of a table storing threshold voltages for reading the Y coordinate when an 8-bit A / D converter is used. In this example, the sensitivity of the central portion of the tablet and the portion near the operator is lower than the sensitivity of the left and right end portions of the tablet and the portion far from the operator.
The threshold value for reading the X coordinate is set similarly and stored in the table.

Next, the operation of the pressure-sensitive coordinate input device will be described with reference to the flowchart of FIG. First, in step S1, the CPU 105 controls the driver circuit to apply, for example, a voltage of 5 V to the terminal XH provided on the right end of the resistance sheet 1 while the terminal XL provided on the left end.
, Terminals YH provided at the upper and lower ends of the resistance sheet 2
, YL are opened, and the voltage at the terminal YL of the resistance sheet 2 in this state is read as a check voltage VTAB via the A / D converter 103. In step S2, the check voltage VTAB is compared with a constant voltage Va, and VTAB
If> Va is not satisfied, it is determined that the input pen has not pressed the resistance sheet, and the process returns to step S1.

If VTAB> Va holds, the flow advances to step S3 to control the driver circuit and to connect 5 to terminal XH.
While applying V, 0 V is applied to the terminal XL, and the terminals YH and YL are opened. In this state, the voltage of the terminal YL is read through the A / D converter 103 (X coordinate reading input).

In step S4, a process of correcting the read X coordinate is performed. This correction process is for compensating for errors caused by an increase in contact resistance between resistance sheets and errors caused by chattering when the pen pressure is weak. 31026
No. 2 is described in the specification.

Next, in step S5, the driver circuit is controlled to apply 5 V to the terminal YH, apply 0 V to the terminal YL, and open the terminals XH and XL. In this state, the voltage of the terminal XL is changed to the A / D converter 103.
(Y coordinate reading input). Step S6
Then, the same correction as in step S4 is performed on the Y coordinate.
In step S7, the check after reading the coordinates and the check before reading the next coordinates are performed in common with each other. That is,
In order to determine the validity of the read coordinates, it is checked whether or not VTAB> Va + Vb holds by referring to the table. If this expression holds, it is determined that the read coordinate data is valid, and the process proceeds to step S9. If not, the read coordinate data is invalid and skipped in step S8. And then step S
Go to 9.

In step S9, it is determined whether or not n pieces of coordinate data have been input. If n pieces of coordinate data have been input, the process proceeds to step S10; otherwise, the process proceeds to step S12. In steps S12 and S13, a check before reading is performed as in steps S1 and S2.
That is, the check voltage of the tablet is read in step S12, and it is checked in step S13 whether VTAB> Va is satisfied. If this formula does not hold, it is determined that the input pen has not pressed the resistance sheet, and the process returns to step S12. If this holds, the process from step S3 is repeated.

In step S10, the read n coordinate data are averaged. In step S11, the averaged coordinate data is stored in the RAM as data indicating the position of the pen.
107.

[0020]

According to the present invention, there is provided a pressure-sensitive coordinate input device comprising: a table for storing a threshold for judging the validity of read coordinate data with an address individually assigned to each area of a pressure-sensitive surface; Means for comparing a threshold value at an address corresponding to the read coordinate data with a check voltage corresponding to the pressing force of the pressure-sensitive surface output from the pressure-sensitive tablet, and the threshold value stored in the table. Is a pressure-sensitive tablet
The sensitivity of the center part of the
Lower than the sensitivity of the left and right ends of the
It is set to become. Therefore, it is possible to freely set the sensitivity of the pressure-sensitive surface over the entire surface, and it is possible to effectively prevent erroneous input due to hand touch on the pressure-sensitive surface, and to vary the sensitivity even when the size of the tablet is increased. One
Can be easily corrected .

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining the operation of a pressure-sensitive coordinate input device according to the present invention.

FIG. 2 is a diagram showing a table storing threshold values for reading a Y coordinate.

FIG. 3 is a block diagram of a pressure-sensitive coordinate input device according to the present invention.

FIG. 4 is a timing chart for explaining a coordinate reading operation of the pressure-sensitive coordinate input device of the present invention.

FIG. 5 is a diagram for explaining an output operation of the pressure-sensitive tablet.

FIG. 6 is a diagram for explaining an output operation of the pressure-sensitive tablet when a hand is touched.

[Explanation of symbols]

 Reference Signs List 101 pressure-sensitive tablet 102 driver circuit 103 A / D converter 104 tablet voltage detection circuit 105 CPU 106 ROM 107 RAM

Claims (1)

(57) [Claims] 1. A pressure-sensitive coordinate input device having a pressure-sensitive tablet composed of a resistance sheet, wherein a threshold value for determining the validity of read coordinate data is individually set for each area of a pressure-sensitive surface. And a means for comparing the threshold value at the address corresponding to the read coordinate data with a check voltage corresponding to the pressing force of the pressure-sensitive surface output from the pressure-sensitive tablet. Prepared , front
The threshold value stored in the table is
Pressure sensitive tablet for sensitivity in the center and near the operator
Lower than the sensitivity of the left and right ends of the
A pressure-sensitive coordinate input device, characterized in that the coordinate input device is set to: