CN114816081A

CN114816081A - Low-cost high-reliability keyboard implementation scheme

Info

Publication number: CN114816081A
Application number: CN202210467651.6A
Authority: CN
Inventors: 谭晓强; 李俊丰; 蒋仁杰; 郭斌; 李亚
Original assignee: Changsha Ruiyi Microelectronics Co ltd
Current assignee: Changsha Ruiyi Microelectronics Co ltd
Priority date: 2022-04-29
Filing date: 2022-04-29
Publication date: 2022-07-29
Anticipated expiration: 2042-04-29
Also published as: CN114816081B

Abstract

The invention discloses a keyboard implementation scheme, which comprises row lines, column lines, keys, a ghost-proof resistor, a terminal resistor, an analog-to-digital converter and a judgment logic.

Description

Low-cost high-reliability keyboard implementation scheme

Technical Field

The patent of the invention relates to a keyboard implementation scheme.

Background

At present, most of keyboards on the market adopt a matrix type implementation scheme, and the matrix type scheme has the characteristics of simple principle, less resource requirements and the like. However, the matrix scheme has its inherent disadvantages, and fig. 1 is a schematic diagram of an original 2 by 2 matrix keyboard, where 101 and 102 are column lines, 103 and 104 are row lines, 105, 106, 107 and 108 are keys, and one end of each key is connected to one row line and the other end is connected to one column line. The keyboard in fig. 1 performs key detection in a scanning mode, first, the row line 103 is connected to the detection end, then the column line 101 is connected to the ground, if only the key 105 is pressed at this time, the ground can be detected through a path, namely the row line 103, the key 105 and the column line 101, so as to judge that the key 105 is pressed; next, row line 101 is disconnected from ground, row line 102 is connected to ground, if only key 106 is pressed at this time, then, through the path, row line 103, key 106 and column line 102 detect ground, so as to determine that key 106 is pressed, so that the key connected to row line 103 is scanned completely, next, row line 104 is connected to the detection circuit, and the above-mentioned process is repeated to determine whether

keys

107 and 108 are pressed. However, the original matrix scanning scheme has inherent problems, for example, when the row line 103 is connected to the detection end, when the column line 101 is scanned, if the key 105 is not pressed at this time, but the

keys

106, 107 and 108 are pressed simultaneously, then the system may consider that the key 105 is pressed when the keys are detected through the paths of row line 103, key 106, column line 102, key 108, row line 104, key 107 and column line 101, and this condition that when multiple keys are pressed simultaneously, the wrong judgment is caused is called ghost in the field of keyboard design and is also called ghost key. The existence of ghost seriously affects the use feeling of the keyboard, and in order to avoid ghost, the simplest way is that when the system detects that a plurality of keys are pressed simultaneously, the keyboard system does not output any information or outputs a fixed code, so that the number of the keys pressed simultaneously by the keyboard is limited, and key collision is caused.

To avoid ghosting and to make all keys immune, it is most common practice in the art to add anti-ghost diodes, fig. 2 is a schematic diagram of a 2 by 2 matrix keyboard using anti-ghost diodes, and in contrast to the non-ghost scheme of fig. 1, fig. 2 is a schematic diagram of a 2 by 2 matrix keyboard in which a diode is connected in series between a row line and a key, the positive terminal of the diode is connected to the row line, and the negative terminal is connected to the key. If the key 205 is scanned, then ground may be detected by way of row line 203, anti-ghost diode 209, key 205, and column line 201; if key 205 is not pressed, but

keys

206, 207, and 208 are pressed, the communication path between row line 203 and column line 201 is interrupted due to the anti-ghost diode 212 being in a reverse biased state, as compared to the design without anti-ghost scheme in fig. 1, so that key 205 is not erroneously detected as being pressed, thereby achieving the anti-ghost purpose.

The invention discloses a design and a detection scheme for preventing ghost by adopting resistance, which can realize ghost prevention design with low cost and can manufacture a low-cost dash-free ghost-proof keyboard by adopting the scheme.

Disclosure of Invention

The invention provides a keyboard scheme, which is characterized in that: contain the rowline, the column line, the button, prevent ghost resistance, the terminal resistor, analog to digital converter and decision logic, wherein, rowline and column line form the matrix layout, all connect through a button and a ghost resistance who establishes ties between every rowline and every column line, a terminal resistor is all connected to every rowline, every terminal resistor can be received first electric potential or second electric potential through corresponding switch, every column line all can be connected to first electric potential or second electric potential through corresponding switch, every rowline all is connected to analog to digital converter's input interface, analog to digital converter converts the voltage on the rowline into corresponding digital value, and give decision logic with the digital value after the conversion, decision logic is according to the threshold value of settlement, judge whether corresponding button is pressed down.

Preferably, the anti-ghost resistor may be a resistor in a physical form, or a resistor formed by a hardware wiring.

Preferably, the termination resistor can be a resistor in a physical form or a resistor of a hardware wiring route; each row line corresponds to a termination resistor, or a plurality of row lines are time-multiplexed by a resistor less than the number of row lines through a switch.

Preferably, the analog-to-digital converter can convert the analog signal into a 1-bit digital signal or a multi-bit digital signal.

Preferably, the decision threshold of the decision logic is a fixed value, or a dynamically adjusted value;

preferably, all the keys are set as a uniform judgment threshold value, or some keys are individually set as the judgment threshold values;

preferably, the termination resistor, the first potential, the switch, the second potential, the analog-to-digital converter and the decision logic are independent devices, or are partially integrated into a device, or are fully integrated into a device.

In summary, the keyboard scheme of the present invention can determine whether the keyboard key is pressed through the ghost-proof resistor and the determination logic thereof, so as to eliminate the interference of ghost keys, realize the keyboard ghost-proof design with a low-cost scheme, and achieve that all keys have no conflict.

Drawings

The above and other features, characteristics and advantages of the present invention will become more apparent from the following description in conjunction with the accompanying drawings and embodiments, in which like reference numerals denote like features throughout the figures, and in which:

FIG. 1 shows a keyboard schematic without ghost key prevention scheme

FIG. 2 shows a schematic diagram of a matrix keyboard employing anti-ghost diodes

FIG. 3 shows a schematic diagram of a matrix keyboard employing anti-ghost resistors

FIG. 4 is a schematic diagram illustrating the operation of the 2-by-2 resistive anti-ghost keyboard of FIG. 3

FIG. 5 is a schematic diagram illustrating the operation of the decision logic

Reference numerals:

101, 102, 201, 202, 301, 302-column line

103, 104, 203, 204, 303, 304-row line

105, 106, 107, 108, 205, 206, 207, 208, 305, 306, 307, 308-Key

209, 210, 211, 212-anti-ghost diodes

313, 314, 315, 316-anti-ghost resistors

317, 318-termination resistance

319-first potential

320-second potential

321, 322, 323, 324, 325, 326, 327, 328-switch

329-A/D converter

330 — decision logic.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Embodiments of the present invention will now be described with reference to the accompanying drawings in detail. Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Further, although the terms used in the present invention are selected from publicly known and used terms, some of the terms mentioned in the description of the invention may be selected by the applicant at his or her discretion, the detailed meanings of which are described in relevant parts of the description herein. Further, it is required that the invention is understood, not simply by the actual terms used but by the meaning of each term lying within.

The first embodiment is as follows:

the resistance anti-ghost principle of the present invention is illustrated below by taking a 2 by 2 matrix keyboard as an example. As shown in fig. 3, which is a schematic diagram of a 2 by 2 resistance anti-ghost matrix keyboard implemented by anti-ghost resistors according to the present invention, 301 and 302 in fig. 3 are column lines; 303. 304 is a row line; 305. 306, 307, and 308 are keys; 313. 314, 315 and 316 are anti-ghost resistors with resistance values of R1, R2, R3 and R4, respectively; 317. 318 is a terminal resistor with resistance values Rp1 and Rp 2; 319 is a first potential, voltage V1; 320 is a second potential, voltage V2; 321, 322, 323, 324, 325, 326, 327, 328 are switches; 329 is an analog-to-digital converter; 330 is decision logic. In FIG. 3,

keys

305, 307 have one end connected to column line 301 and the other end connected to one end of

anti-ghost resistors

313 and 315, respectively;

keys

306 and 308 have one end connected to column line 302 and the other end connected to one end of

anti-ghost resistors

314 and 316, respectively; the other ends of

anti-ghost resistors

313 and 314 are connected to row line 303; the other ends of

anti-ghost resistors

315 and 316 are connected to row line 304; column line 301 is connected to switch 321 and one end of switch 322, the other end of switch 321 is connected to second potential 320, the other end of switch 322 is connected to first potential 319; column line 302 is connected to one end of switch 323 and switch 324, the other end of switch 323 is connected to second potential 320, the other end of switch 324 is connected to first potential 319; the row line 303 is connected to a termination resistor 318, the other terminal of the termination resistor 318 is connected to a switch 327 and a switch 328, the other terminal of the switch 327 is connected to the second potential 320, and the other terminal of the switch 328 is connected to the first potential 319; the row line 304 is connected to one terminal of a termination resistor 317, the other terminal of the termination resistor 317 is connected to one terminal of a switch 325 and a switch 326, the other terminal of the switch 325 is connected to the second potential 320, and the other terminal of the switch 326 is connected to the first potential 319; the

row lines

303 and 304 are connected to input ports of an analog to digital converter 329, the output ports of the analog to digital converter 329 being connected to decision logic 330. The operation of the 2 by 2 resistive anti-ghost matrix keyboard of fig. 3 is shown in fig. 4, where the waveforms in the third and fourth rows of fig. 4 depict the operation of switch 321, switch 324, switch 323, and switch 322, with a high waveform indicating that the switch is closed, a low waveform indicating that the switch is open, both switch 325 and switch 327 are open, and both switch 326 and switch 328 are closed. At time t1, ADC 329 selects row line 303 for quantization while

switches

321 and 324 are closed, at which time key 305 is asserted, and the voltage on row line 303 is discussed in four cases, according to the combination of switch presses, first case-no key press, at which time there is no path between first potential 319 and second potential 320, and the voltage on row line 303 is equal to V1; the second case, where key 305 has not been pressed, but key 306 on row line 303 is pressed, at which point the voltage on row line 303 is at value V1, in which case keys on other row lines have no effect on the voltage on row line 303; in the third case, where only key 305 is pressed, and there is a path between first potential 319 and second potential 320, switch 328, termination resistor 318, row line 303, anti-ghost resistor 313, column line 301 of switch 305, and switch 321, where the voltage on row line 303 is equal to V1+ Rp2 (V2-V1)/(Rp2+ R1); in the fourth case, key 305 is pressed, key 306 on the same row line is also pressed, and two paths exist between second potential 320 and first potential 319, the first path being switch 321, column line 301, key 305, anti-ghost resistor 313, row line 303, termination resistor 318, and switch 328, and the second path being switch 321, column line 301, key 305, anti-ghost resistor 313, row line 303, anti-ghost resistor 314, key 306, and switch 324; at this point, the voltage on row line 303 is equal to V1+ (Rp2| | R2) × (V2-V1)/((Rp 2| | R2) + R1), where Rp2| | R2= Rp2| R2/(Rp 2+ R2), in which case the keys on the other row lines have no effect on the voltage on row line 303. The analog-to-digital converter quantizes the voltage of the row line 303 into a digital signal and sends the digital signal to the decision logic 330, fig. 5 shows a schematic diagram of the decision principle of the decision logic 304 for the keys under the above four key conditions, and the decision logic sets the decision threshold between V1 and V1+ (Rp2| R2)/((Rp 2-V1)/((Rp 2| R2) + R1), so that it can be determined whether the key 305 is pressed according to whether the voltage on the row line 303 exceeds the threshold, and even if the key 305 is not pressed and other keys cause a path between the first potential 319 and the second potential 322, the voltage on the row line 303 does not exceed the decision threshold, and therefore no ghost image is generated. After making the determination for key 305, when time comes to time t2 in fig. 4, analog-to-digital converter 329 still selects row line 303 for quantization, while

switches

321 and 324 are open,

switches

323 and 322 are closed, and determination is made whether key 306 has been pressed, in a similar manner as described above for key 305. After the time point t2, all the keys on the row line 303 are scanned, then the keys on the row line 304 are scanned, the row line 304 is selected by the digital converter 329 for quantization, the key 307 is judged at the time point t3, the key 308 is judged at the time point t4, and the judgment process is similar to that of the key 305.

In the first embodiment, only the implementation of the keyboard with 2 rows, 2 columns and 4 switches is described, in another embodiment, the keyboard can be extended to a keyboard with M rows, N columns and at most M times N keys, when a certain key is judged, the row lines are all connected to a first potential, the column line connected with the key is connected to a second potential through the corresponding switch, and the other column lines are all connected to the first potential through the corresponding switches;

in embodiment one, the column line and the row line can distribute in the different aspect of circuit entity, also can distribute in the same aspect of circuit entity, if column line and row line distribute in the same aspect of circuit entity, need to use the wire jumper when column line and row line are criss-cross, can use low resistance or zero ohm resistance to do the wire jumper, also can use the wire to do the wire jumper, also can use carbon film resistance to do the wire jumper, also can use other conducting material to do the wire jumper, the resistance of wire jumper will be less than prevent ghost resistance, avoid wire jumper resistance to cause the influence to the button judgement.

In the first embodiment, the anti-ghost resistor can be realized in the form of a physical resistor, and can also be realized by a resistor of a hardware wiring route.

In the first embodiment, the termination resistor may be implemented in the form of a physical resistor, or may be implemented in the form of a resistor of a hardware wiring route.

In the first embodiment, the termination resistor, the first potential, the switch, the second potential, the analog-to-digital converter, and the determination logic may be separate devices, or some or all of them may be integrated into one device.

In the first embodiment, the determination threshold values of the determination logic for different keys may be the same value or different values.

In the first embodiment, the decision threshold of the decision logic may be a fixed value or a dynamically changing value.

In the first embodiment, the analog-to-digital converter performs conversion only for one row line at the same time, in the other embodiment, the analog-to-digital converter may perform conversion for a plurality of row lines simultaneously, and correspondingly, the determination logic may also perform determination for the output of the analog-to-digital converter simultaneously.

In one embodiment, the keys are scanned row by row in groups of row lines, and in another embodiment, the keys are scanned column by column in groups of column lines.

In one embodiment, the analog-to-digital converter converts the row line voltage into a corresponding multi-bit digital value, and in another embodiment, the analog-to-digital converter may output only a 1-bit digital value, and additionally receives a reference voltage, and the analog-to-digital converter represents the comparison result by using a 1-bit output by comparing the row line voltage with the reference voltage.

In the first embodiment, in the process of judging the key, the row line is connected to the first electric potential, the column line where the judged key is located is connected to the second electric potential, the other column lines are connected to the first electric potential, and then the judgment logic judges the state of the key by using the absolute voltage value of the row line quantized by the analog-to-digital converter. In another embodiment, the relative value of the line voltage can be obtained through two times of quantization to judge the state of the key, wherein the first quantization is consistent with the process, and the judgment logic obtains the first quantization result; during second quantization, the row lines are all connected to a second electric potential, the row line where the judged key is located is connected to the first electric potential, the other row lines are connected to the second electric potential, the analog-to-digital converter sends the quantization result to the judgment logic, the result is a second quantization result, the judgment logic performs difference on the two quantization results to obtain the relative value of the line voltage of the row lines in the two quantization processes, and the key state is judged according to the relation between the relative value of the line voltage and the threshold voltage. In another embodiment, the two quantifications are performed in the same manner, but the decision logic does not perform a difference between the two quantifications, but rather performs two key state decisions for the two quantifications based on two different thresholds, and determines that the key has been pressed if both decisions indicate that the key has been pressed.

While specific embodiments of the invention have been described above, it will be appreciated by those skilled in the art that these are by way of example only, and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the invention.

Claims

1. A keyboard solution, characterized by: the circuit comprises row lines, column lines, keys, anti-ghost resistors, a terminal resistor, an analog-to-digital converter and decision logic, wherein:

the row lines and the column lines form a matrix layout, and each row line and each column line are connected through a key and a serially connected anti-ghost resistor;

each row line is connected with a terminal resistor, and each terminal resistor can be connected to a first potential or a second potential through a corresponding switch;

each column line may be connected to a first potential or a second potential through a respective switch;

each row line is connected to an input interface of the analog-to-digital converter, the analog-to-digital converter converts the voltage on the row line into a corresponding digital value, the converted digital value is sent to the judgment logic, and the judgment logic judges whether the corresponding key is pressed or not according to a set threshold value.

2. A keyboard arrangement according to claim 1, wherein: the anti-ghost resistor may be a resistor in a physical form, or a resistor formed by hardware wiring.

3. A keyboard arrangement according to claim 1, wherein: the terminal resistor can be a resistor in a solid form or a resistor formed by hardware wiring; each row line corresponds to a termination resistor, or a plurality of row lines are time-multiplexed by a resistor less than the number of row lines through a switch.

4. A keyboard arrangement according to claim 1, wherein: the analog-to-digital converter may convert an analog signal into a 1-bit digital signal or a multi-bit digital signal.

5. A keyboard arrangement according to claim 1, wherein: the decision threshold of the decision logic is a fixed value, or a dynamically adjusted value.

6. A keyboard arrangement according to claim 1, wherein: all keys are set as a uniform decision threshold, or some keys are individually set as decision thresholds.

7. A keyboard arrangement according to claim 1, wherein: the terminal resistor, the first potential, the switch, the second potential, the analog-to-digital converter and the decision logic are independent devices, or are partially integrated in a certain device, or are fully integrated in a certain device.