JPS5831629B2 - Pentatsuchi signal shaping circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Ben-touch signal shaping circuit that eliminates unnecessary detection signals due to transient phenomena during input by shaping Ben-touch signals in a tablet, thereby ensuring human power.

The detection disadvantages of conventional tablets will be explained by taking the pressure-sensitive tablet shown in FIG. 1 as an example.

The output signal of such a tablet is
There are three types of signals: Operational amplifier 1, 2.3
is output from.

When there is an input, the pressure-sensitive sheet 10 becomes conductive on the front and back sides of the input point on the plane, and the X-coordinate detection resistor 5 and the y-coordinate detection resistor 6 are electrically contacted at points 11 and 12, as shown by thick lines. ), each current ratio 11/12 and 13/14 depending on the input point position.
The position coordinates of the input point are detected from the change in the input point.

Specifically, a constant current I is generated by a constant current source consisting of an operational amplifier 4 and a reference resistor 9.

The current 12 and i4 are connected to the resistor 7 and the resistor 8.
By converting it into a voltage, the x and y coordinates of the input point can be detected.

Also, the fact that there was an input was a current I.

The operational amplifier 3 can detect and know the voltage drop when the current flows through the reference resistor 9.

(Please refer to Japanese Patent Application Laid-Open No. 55131839 for details of the detection principle of the tablet shown in Fig. 1.) Fig. 2 is a time chart of x, y, and z signals, where ■ is the X coordinate signal waveform, and ■ is the y coordinate signal. Waveform, ■ is a two-signal waveform, ■
indicates the sampling pulse.

At time t1, the pen touches the input surface and a current ■ is generated.

begins to flow, and the x and y coordinate signals rise from time t1 to time t2 of ■ and ■.

During this time, the x and y coordinate signals are in a transient state and cannot indicate the correct pen position.

Between time t4 and time t15, although the input pen is touching the input surface, the pressure of the pen is not sufficient, and the pressure-sensitive sheet 10 momentarily becomes insulated, causing a momentary interruption in the two signals. , y coordinate signals limit the bands of the operational amplifiers 1 and 2, so they are not affected by instantaneous interruptions.

However, if the pulse P at ■ between times t4 and t5
When the sample time point 1 is entered, even though the pen is in the middle of one stroke from time t, the pen leaves the input surface between time t4 and t5.
It is assumed that another stroke has occurred after time t5.

Such a phenomenon is undesirable in patent applications that are characterized by the number of strokes, such as character recognition.

In order to eliminate these drawbacks, the present invention shapes the Bentouch signal (two signals) to enable accurate detection of X and Y coordinates.

This invention will be explained in detail below.

FIG. 3 is a circuit diagram showing an embodiment of the present invention.
1 is the 2 signal input terminal, 22 is the terminal, 23 is the shaped 2
A signal output terminal, 24 is a capacitor, 25 and 27 are retrigger monostable multi-by-breaks, and 26 and 28 are AND gates.

As is well known, an ordinary monostable multi-bibreak outputs a pulse with a fixed time width in response to a trigger input, but the trigger is ineffective during operation.

The retrigger monostable multi-by-break has the characteristic that if a trigger input is applied during operation, it restarts from that point.

(For details, see Yojibe Yokoi (Radio Gijutsusha)
See Digital IC Practical Circuit Manual JP, 390.

) The operation of the circuit shown in FIG. 3 will be explained using FIG. 2 again.

First, when the two signals shown in FIG. 2 (■) are applied to the two-signal input terminal 21, the capacitor 24 is connected to a very short period of time between the two signals (for example, between time t4 and t5 in FIG. 2 (■)).
Perform actions that connect the two.

That is, capacitor 24 acts as a signal connection means.

Also in the X and y coordinate signals shown in FIG. Very short breaks, such as between '5', are connected.

The retrigger monostable multi-by-break 25 generates a pulse with a time width Tm when a falling pulse is applied to the terminal A.

The Q terminal outputs the inversion (NOT).

When the AND gate 26 calculates the logical product of Q and the two signals themselves, 2' as shown from time t6 to t1□ in Figure 2.
Get a signal.

During this time, the signal corresponds to no Bent touch, so Figure 2 ■.

Noise caused by chattering such as from times t6 to t1□ in (2) can be completely removed.

In this way, the retrigger monostable multi 25 and the AND gate 26 act as signal stretching means.

Three-way, retrigger monostable multi-bi break 27 and A
The ND gate 28 is used to remove a transient signal at the rising edge of the bent touch signal, such as that between times t2 and t3 in FIG.

That is, the retrigger monostable multi-by-break 27 is
It is triggered by the falling edge of the pulse applied to the terminal 22, and from this point on, a pulse with a width of Ts is generated.

When this inversion (NOT) is taken out from the Q terminal and ANDed with the signal applied to the terminal 22 at the AND gate 28, the 2' signal is at the front by the Ts width compared to the 2 signal, as shown in Figure 2 (■). is being transcribed.

During this period (during Ts), the 2' signal is in a state where there is no bend touch, that is, there is no input, and the time t shown in Fig. 2
Noise caused by transient phenomena at the start of input such as at times 2 to t3 can be completely removed.

As explained in detail above, the present invention provides a signal connecting means that connects the breaks in a bent-touch signal to form a continuous signal when the time width of the breaks is less than a predetermined time width; When the width is greater than another predetermined time width, the bent touch signal is processed by a signal extension means that extends the signal to a predetermined time, so if the input is incomplete or the input is incomplete. This has the advantage that noise caused by chattering can be prevented from being input.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional pressure-sensitive tablet detection circuit, Fig. 2 is a time chart showing output signals of the pressure-sensitive tablet shown in Fig. 1, and Fig. 3 shows an embodiment of the present invention. It is a circuit diagram. In the figure, 1.2 and 3.4 are operational amplifiers, 5 is an X-coordinate detection resistor, 6 is a y-coordinate detection resistor, 7 and 8 are resistors, 9 is a reference resistor, 10 is a pressure sensitive sheet, and 11° 12 is the input point, 2
1 is the Z signal input terminal, 22 is the terminal, 23 is the output terminal, 2
4 is a capacitor, 25° 27 is a retrigger monostable multivibrator, and 26° 28 is an AND gate.

Claims (1)

[Claims] 1. A signal connecting means that inputs a pen touch signal generated by a pen touch, and connects the breaks in the pen touch signal to make a continuous signal when the time width of a break in the pen touch signal is less than a predetermined time width; 1. A pen touch signal shaping circuit comprising a signal train extending means for extending a signal train to a predetermined time when the time width of the middle part is longer than another predetermined time width.