JPS62143118A - Method for scanning key - Google Patents

Abstract

PURPOSE:To obtain a key scanning method characterized by a rapid scanning speed and low current consumption by setting up a scanning signal to the 1st output level to scan one line and then inverting the scanning signals for all lines against the 1st output level only for a prescribed period. CONSTITUTION:A microcomputer 1 controls a system using touch keys. Data are written from the microcomputer 1 to a latch 2 in accordance with necessity and data corresponding to key entry is inputted from an input port 3 to the microcomputer 1. After executing all phi clear of the latch 2, necessary data are written, a key input is decided, and when the existence of key input is decided, key input processing is executed. When there is no key input, all phiclear of the latch 2 is once executed and then necessary data are rewritten to scan the succeeding line. Since the output level of a scanned line is rapidly turned to '0', rapid key scanning can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a key scanning method for a keyboard such as a touch panel.

(Conventional technology) The sixth method for key scanning on conventional touch panels, etc.
This will be explained using figures.

Scanning data is written into the latch 700 from a microcomputer (not shown), and the scan result is returned to the input port door 50. 800 to 802 are diodes that prevent current from flowing backwards.

For example, set b A' point to output level 1 and key 600 to 6.
Consider the case where after scanning 02, the output level is set to 1 at point P' and keys 610 to 612 are scanned. When scanning, only one of A' g B' @ O' becomes output level 1, and all others become O. This is because when multiple lines reach output level 1, it becomes difficult to know which line's key was pressed.

However, if B' is 1 and C' is 0, then the key 610.62
0 or two keys 611 and 621 or key 6
When 12 and 622 are pressed at the same time, if the diode 802 were not present, current would flow from B' through al+ to the buffer 652, and if the buffers 651 and 652 were connected, a large current of ≠ 5 would flow. This may cause unnecessary current consumption and destruction of the buffers 651 and 652.

Diodes 800-802 are installed to prevent this.

However, once the AZ point becomes 1, for example, the capacitor t660 generated between the panel and the ground is charged with electric charge, but even if it becomes 0, there is a diode 800, so the only thing that can be done is to create a discharge. diode 8
(This is caused by a leakage current in the opposite direction of 00.) As mentioned above, if the potentials of A' to C' are at output level 1 at multiple locations, it is impossible to know which line was pressed. For this reason, in the past, scanning of one line was completed and the scanning of the next line was started after sufficient time had elapsed for the discharge to be completed.

Additionally, a discharge resistor was placed in parallel with the capacitor in order to increase the scan speed, but this resulted in an increase in current consumption due to the discharge resistor.

(Problem to be Solved by the Invention) Therefore, in the conventional technology, even after scanning one row, the scan of the next row cannot be started until the charges are sufficiently discharged. There was no @.

Furthermore, in order to perform high-speed key scanning, a resistor for discharging the capacitor must be inserted in parallel with the capacitor, leading to an increase in current consumption.

The present invention solves the above problems and reduces scanning stray electricity quickly.
Another object of the present invention is to provide a key scanning method for a touch panel or the like with low current consumption.

(Measures to Solve the Problem) The present invention scans one row by setting the scanning signal to a first output level, and then outputs the scanning signal to all rows for a predetermined period at the first output level. level and then inverts the scanning signal to the first line to scan the next row.
It is characterized in that it is carried out at an output level of .

(Operation) In the case of the present invention, after one row is scanned, the charges charged during the scan of the previous row are rapidly discharged before moving on to the scan of the next row.

(Embodiment) FIG. 1 shows an example of an apparatus to which the key scanning method of the present invention is applied. Here, microcomputer 1
The system is controlled using touch keys. Also, data is written from the microcomputer 1 to the latch 2 as necessary, and data corresponding to the key input is read from the input board 3 to the microcomputer 1.
It will be done.

FIG. 2 is a diagram showing the state of points A to F in FIG. 1 when the key scanning method of the present invention is applied.

The present invention will be explained in detail using FIG.

In section (a), all points ABC become output level 0, and the charges accumulated between the touch key electrode and the ground are discharged. In the interval (υ, only A is set to output level 1, and B, C
n High impedance and keys 101 to 1 in this section
05 is pressed.

If none of the final nails 101 to 103 are pressed, the process moves to section 1 (C).

In the interval (c), the psychic charge accumulated between the electrode and the ground during the interval (b) is discharged. Similarly below, section (a)
Then, it is checked whether any of the keys 201 to 205 has been pressed and in the interval (e), the charge accumulated in the interval (ω) is discharged.Furthermore, in the interval (f), it is checked whether any of the keys 301 to 303 has been pressed. The state in the intervals (a), (c), (e), and (m will be explained in more detail using FIG. 3).

First, between the touch panel and the ground, place 30 in Figure 3.
The capacitance shown in 31.32 occurs.

In section (a), the charges charged in these capacitors are first discharged to perform initialization.

In section (C), the output level at point A becomes 0, and a discharge of capacity t50 is performed. At this time.

Points 2 and 0 also have an output level of 0.

The section (c) will be explained in detail as follows.

After scanning keys 101 to 106, key 20 is next.
Since the scanning moves from 1 to 203, it would be undesirable for the potential at point C to rise, so the output level is set to 0, for example. At the same time, point %B is also set to output level 0. So tri, if point C is O and point P is 1, then
For example, when keys 201 and 301 are pressed at the same time,
This is because the current flows around from point P to point C, and as a result, the output buffers 54 and 35 are connected, resulting in a large current flowing and wasting the current.

In addition, in the time chart of FIG. 2, in the section (C), the 0. The 0 at point B and the 0 at point C are happening at the same time.

Here, as mentioned earlier, O1I'l of the s B HC point
j must be simultaneous, but it is not necessary for the 0 at point A to occur at the same time; the 0 at point A and the 0 at point B and 0 may be at different timings.

Also, section (b) t (a) s (f) t (h)
Now, any one of the three points A-1' is at output level 1, but when point A is at output level 1 at 9 o'clock as well, to avoid current circulation,
Point B and 0 are in a high impedance state and are separated by an output buffer of 54.35 degrees.

FIG. 4 shows all the data that should be input from the microcomputer 1 to the latch 2 in order to operate the time chart shown in FIG. 2. The * mark indicates that the output buffer is separated, so any value is acceptable. Also, here, the data line input from the microcomputer 1 to the latch 2 is 6.
This number is for convenience of explanation, and the actual number of data lines may be 8, 16, etc.

FIG. 5 shows how the key scan is performed while the data shown in FIG. 4-2 is being written into the latch 2.

As shown in Figure 5, after clearing latch 2 and writing the necessary data, the KEY input is checked, and if it is determined that the KEY is powered manually, the KKY input processing is performed, and the KEY input is completed. If there is no such data, clear the hair latch 2, write the necessary data again, and move on to scanning the next line. Then, this process is repeated when the KEY input is 1.

In addition, in the above embodiment, in the section (c) of FIG.
The output levels at points B and C are set to O, but they can also be set to a high impedance state instead of 0.
This is because since Fi and the output buffers 34 and 35 are separated, the current from point A will not be divided by 1. This means that other intervals (θ), (g), (t
The same can be said about l.

(Effects of the Invention) As described above in detail, in the case of the present invention, when the key scan of one row is completed, the output level of the scan signal for all rows is always lowered to low. Charges that were charged during scanning of the previous row are rapidly discharged, and therefore the output level for the scanned row quickly becomes OK, allowing high-speed key scanning.

1. Since there is no need for a resistor for discharging the capacitance for high-speed scanning, current consumption can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of a keyboard to which the present invention is applied, and FIG. 2 is a time chart explaining the present invention in detail. FIG. 3 is a diagram for further explaining FIG. 1, and is an explanatory diagram of the movement of charges charged in the capacitance generated between each row and the ground. FIG. 4 is a diagram showing what kind of data 5 is required to perform the operation shown in the time chart of FIG. 2, and FIG. 5 is a flowchart showing the operation of the present invention in detail. FIG. 6 is a diagram showing a conventional key scanning method. 30.31.52...Capacity 55.54.55...Output buffer or more Applicant Seiko Epson Co., Ltd. Agent Patent attorney Tsutomu Mogami and 1 other person J Figure 1 B, -------W- -----------c
----------------1-1-----Figure 2 Figure 3 Figure 4-1 Figure 4-2 Figure 5

Claims (1)

[Claims] Scanning one row is performed with the scanning signal at the first output level, then the scanning signals for all rows are inverted from the first output level for a predetermined period, and then the next row is scanned at the first output level. A key scanning method characterized in that the scanning signal is set at the first output level.