JPS6233618B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field of the Invention) The present invention relates to a device for inputting two-dimensional coordinates of an arbitrary point on a flat input surface into a computer, etc. by pressing the point with a writing instrument, stylus, etc. In particular, the present invention relates to an input device that obtains coordinate data based on a voltage value generated on a resistor sheet.

(Prior art and its problems) A two-dimensional coordinate input device using a resistor sheet is
It is attracting attention as an inexpensive and easy-to-use input device that does not require a pen with a cord.

However, since this input device measures the voltage at a single point on the input surface formed by a large-area resistor sheet, it has the disadvantage that the output coordinate values fluctuate due to induced noise from human hands, etc. It was hot. Therefore, it has been considered to prevent noise induced from the human body by providing shield electrodes with insulating layers above and below the resistor film that constitutes the input surface. However, when a shield electrode is provided, due to the capacitance between the resistor film and the shield electrode,
The waveform of the transient response observed after switching the analog switch that changes the Y coordinate detection mode to the desired mode is highly dependent on the variation in contact resistance of the contact point of the resistor film that occurs when the pen is moved with light pen pressure. I decided to do it. For this reason, the output coordinates are not affected by the human body, but due to fluctuations in contact resistance when moving the pen with light pressure,
Unexpected and discontinuous coordinate values were sometimes output.

Conventionally, as a countermeasure to this problem, when unexpected coordinate values are obtained, stable coordinate values are output by excluding them.

An example of such a conventional configuration will be explained using FIG. 1. As shown in the figure, the coordinate input device includes a resistor sheet 1, a current source 2, an analog switch 3, a differential amplifier 4, an AD converter 5, It consists of a pen detection circuit 6, a main arithmetic and control unit 7', and an interface circuit 8.

In the above configuration, the operation up to obtaining the X, Y coordinate data will be described below.

First, the analog switch 3 is set to the X coordinate detection side, and after a certain period of time (for example, a value determined by the time delay due to the capacitance between the resistor and the electrode, or the response time of the analog switch 3 and the differential amplifier 4) has elapsed. ,
The analog voltage corresponding to the X coordinate obtained from the resistor is converted into digital data by the AD converter 5, and the data is sent to the data acquisition circuit 9 of the main processing and control unit 7'. , the data is passed through the demultiplexer 10 to the XO
It is held in register 11. Next, switch analog switch 3 to the Y coordinate detection side, and do the same as above to
Data corresponding to the coordinates is stored in the YO register 12.

On the other hand, the data processing circuit 1 of the main arithmetic and control unit 7'
3 converts the obtained data to the required resolution and converts the value of the pen status register 14 in the data processing circuit 13 to the pen detection circuit 6 supplied via the IO port 21 and the sequence control circuit 19.
The data is set according to the output of the interface circuit 8 at the subsequent stage. This data processing circuit 1
In step 3, register the data already sent.
It is held in XPRIV, YPRIV15, 16, and new coordinate data is stored in X0, Y0 registers 11, 12.
, the inter-coordinate distance discrimination circuit 17
X0, Y0 registers 11, 12 and register XPRIV,
Compare the difference (distance) with the data stored in YPRIV15, 16 with the value set in advance as an allowable range, and if it is within the allowable range, register
XPRIV, YPRIV15, 16, X0, Y0 register 1
Transfer the latest data of 1 and 12 and output them as valid coordinates. However, if accurate analog voltage cannot be obtained due to factors such as light pen pressure, the distance between the data in X0 and Y0 registers 11 and 12 and the data in registers XPRIV and YPRIV15 and 16 will exceed the set value. In this case, the latest data in the X0 and Y0 registers 11 and 12 is considered to be coordinate noise and is invalidated to remove the noise.

However, in the above configuration, because the analog switch 3 was set to each of the X and Y coordinate detection modes and the coordinate data was obtained by blindly performing AD conversion after a certain period of time had elapsed, It was not possible to determine noise using a completely analog voltage level. Therefore, since noise is determined only by comparing the distance between the coordinates of two points, it is necessary to strongly suppress noise to increase reliability, which limits the pen speed that can be input. In addition, since the distance is always determined based on the coordinates and distance that were sent as valid last time, if the pen speed temporarily increases and it is determined to be noise, the last valid press of the pen may The next effective coordinate could not be obtained unless the user moved closer to the point or lifted the pen, making operability worse.

(Objective of the Invention) Therefore, an object of the present invention is to provide a device that can remove coordinate noise caused by unstable conditions such as when the pen pressure is light, and can always output stable coordinate data. It is about providing. Another object of the present invention is that when the pen is temporarily moved at a speed exceeding the allowable range, even if it is determined to be coordinate noise, the speed returns to within the allowable range. Sometimes it is possible to immediately output coordinate data to improve operability.

(Summary of the Invention) In order to achieve the above object, the present invention samples a plurality of voltage values corresponding to the X and Y coordinates, and samples at least two of each data sampled for each X and Y coordinate. In addition to determining whether the deviation of the data is within a predetermined permissible variation range, the X and Y coordinates of approximately the same pressing point are similarly sampled to determine whether the deviation is within the permissible variation range. Only when the data are allowed together,
The previous data and the latest data are compared and determined, and when it is determined that the data is valid, the latest data is output.

(Embodiments of the Invention) Details of the present invention will be explained below with reference to embodiments shown in FIG. 2 and subsequent figures.

FIG. 2 shows an outline of the coordinate input device of the embodiment, and the coordinate input device includes, as shown in the figure, a resistor sheet 1, a current source 2, an analog switch 3, a differential amplifier 4, an AD converter 5, It consists of a pen detection circuit 6, a main arithmetic and control unit 7, and an interface circuit 8. FIG. 3 shows the inside of the main arithmetic and control unit 7 in more detail. circuit 1
7, data processing circuit 13, sequence control circuit 1
9th grade is available. In addition, each circuit 13,
17, 18, and 19 each further have functional means (circuits) to be described later, which will become clear from the following explanation of the operation.

In the initial state, there is no input to the resistor sheet 1, and the pen flag 20 of the sequence control circuit 19 is reset.If there is a pen input in such a state, the I/O is output from the pen detection circuit 6.
A signal is sent to the sequence control circuit 19 through the port 21, and the following data collection sequence starts.

By supplying the above signal, the sequence control circuit 19
First, the state of the pen flag 20 is determined.
Since the pen flag 20 has been reset, the main flag 22 is also reset. main flag 22
When is reset, the sequence control circuit 19
The transient flag 23 of the transient response monitoring/data collection circuit 18 is reset, and the transient response monitoring/data collection circuit 18 is activated to perform the first data collection. That is, the analog switch 3 is switched to the X coordinate detection side, and after approximately 0.9 msec has elapsed, AD conversion is performed continuously n times, and the digital data obtained by the AD converter 5 is sent to the maximum value/minimum value judgment circuit. 24 as necessary through
It is set in the MAX register 25 and MIN register 26. On the other hand, the n-time sampling data is summed by the adder 27 and added to the SUM register 2.
It is held at 8. After this sum is taken, SUM
The contents of the register are determined by the demultiplexer 10.
Moved to X0 register 11. On the other hand, the maximum value and minimum value of the n-times sampling data are calculated by the subtraction circuit 29.
The difference is determined by the comparison circuit 30 and compared with the set value, and it is determined whether the difference is within the allowable variation range, in other words, whether the sampled data is stable and reliable. .

That is, FIG. 4 shows the correspondence with the actual analog voltage waveform, and in the figure, the waveform 34 is the voltage waveform observed at the input terminal of the AD converter.

Now, after switching the analog switch 3 to the X coordinate detection mode at time 0, after a predetermined time td has elapsed,
Sampling by AD conversion is performed continuously at least twice at the timing indicated by 35 in the figure.
When the difference between the maximum and minimum values of the series of sampling values (each point represented by a black circle in the figure) is within the set value range indicated by the diagonally shaded band 36, the resistor sheet 1 The contact state is determined to be stable. However, as shown in FIG.
If the difference between the maximum value and the minimum value exceeds the range of the set value 36 due to unstable contact status, it may cause coordinate noise. - The data acquisition circuit 18 sets its transient flag 23.

Next, by switching the analog switch 3 to the Y coordinate detection side, data 12 to be stored in the Y0 register is obtained in the same way as above, and if the difference between the maximum value and the minimum value is outside the allowable range, the transition Ent flag 23 is set.

The transient flag 23 can be reset only from within the sequence control circuit 19, and can be reset only from within the sequence control circuit 19.
Now you can't reset it. Therefore, if the transient response is unstable when detecting either the X coordinate or the Y coordinate, the transient flag 23 is set. Transient flag 2 is set after the operation of
3 may be checked.

If the difference between the data sampled by the comparator circuit 30 is outside the allowable range and the transient flag 23 is set as described above, control is transferred to the reject control circuit 31 of the sequence control circuit 19. Reject control circuit 3
1 determines whether the unstable condition that caused the transient flag 23 to be set is temporary, and controls the entire sequence as necessary.

As described above, transient response monitoring/data acquisition circuit 1
After completing the series of operations in step 8, the transient flag 2
If 3 is not set, the data in the X0, Y0 registers 11, 12 is guaranteed to be approximately accurate data.

After that, the state of the main flag 22 is checked in the sequence control circuit 19, and if it is not set, the X0, Y0 registers 11, 12 are checked.
After transferring the data within to the X1 register 32 and Y1 register 33 and setting the main flag,
The transient flag 23 is reset again in the same manner as described above, and the transient response monitoring/data collection circuit 18 is activated to perform the second data collection.

When almost accurate data is set in the X0, Y0 registers 11, 12 again by the second data collection, the main flag 22 is checked. If the X1, Y1 registers 32, 33 already hold reliable and accurate data collected last time, the main flag 22 is set, so in this case, the control is 11, 12 to X1, Y1 registers 32, 32
In other words, the content is transferred to the distance determining circuit 17, which is a means for determining coordinate data. A known appropriate means is used to calculate this distance, and the calculated data in the X0, Y0 registers 11, 12 and the data in the X1, Y1 registers 3 are used.
The distance between the two points, which is the difference between the data Nos. 2 and 33, that is, the difference between the latest coordinate data and the previously collected coordinate data, is compared with a set value by the distance discrimination circuit 17. If this distance is larger than the set value, the sequence control circuit 19 transfers control to the first data collection. Conversely, if the distance is within the set value, X0, Y0 register 1
The data processing circuit 13 treats the data held in 1 and 12, that is, the latest data, as true data.
Send to.

The data processing circuit 13 performs data smoothing processing as necessary and sends the data to the subsequent interlace circuit 8, and also sets and resets the pen flag 20. When accurate coordinate data is thus output, the main flag 22 is set, and the sequence control circuit 19 returns the operation to the next data collection processing routine.

Therefore, if accurate coordinate data of the pen-down state had been output immediately before, the main flag 22 has been set as described above, and the routine immediately moves to the second data collection routine. That is, in this case, as soon as new coordinate data is set in the X0, Y0 registers 11, 12, the inter-coordinate distance determining circuit 17 will operate. As a result, when the pen continues to move stably, the distance from the previous effective coordinate is always used for judgment, so only one sampling is required, and the conversion speed does not decrease.

On the other hand, even if the second data collection routine is started immediately, the transient flag 23 may be set because the contact of the resistor sheet 1 is unstable at that point. In such a case, the sequence control circuit 19 detects that the transient flag is set at a certain appropriate timing, clears the main flag, and controls the control sequence by treating subsequent data collection as the first data collection. I'm starting to do that. By doing this, for example, if the pen is moved faster than the allowable speed under some conditions, the sampled coordinate point will become invalid because it has moved beyond the set value from the coordinate point previously sent as valid. However, as soon as the pen speed returns to within the allowable range, it becomes possible to output effective coordinates again.

(Effects of the Invention) As described in detail above, according to the present invention, even when pen input is performed with light pressure, it is possible to always output only accurate and stable coordinates. Also, even if the pen is temporarily moved beyond the allowable speed and sampled coordinates are not output as invalid, valid coordinates will be output again immediately when the speed returns to within the allowable range. This makes it possible to improve operability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional embodiment, FIG. 2 is a rough block diagram of an embodiment according to the present invention, FIG. 3 is a detailed block diagram for explaining the operation, and FIGS. The figure shows the voltage waveform observed in the circuit. In the figure, 3 is an analog switch, 5 is an AD converter, 7 is a main arithmetic and control device, 19 is a sequence control device, and 17 is an inter-coordinate distance determination circuit.

Claims (1)

[Claims] 1. Coordinate input means that outputs voltage values corresponding to the X and Y coordinates of the pressing point on the resistor sheet,
a switching means for alternately outputting voltage values corresponding to the X and Y coordinates of the coordinate input means; and a storage means for storing data obtained by sampling a plurality of voltage values corresponding to the X and Y coordinates. , a comparison means for determining whether the deviation of at least two of the sampled data is within a predetermined allowable fluctuation range;
control means for sampling each voltage value of the Y coordinate a plurality of times and newly importing it into the storage means; The comparing means determines whether the deviation between the two pieces of data is within a predetermined permissible fluctuation range, and only when the latest data and the previous data are both within the permissible range, the most recently imported data is determined. The cumulative value of the X and Y coordinates of the previously captured data is compared for each X and Y coordinate by a discrimination means,
An input device characterized in that the latest data is output only when the determination by the determination means is within a predetermined allowable fluctuation range.