CN104898853A - Novel three-terminal tact switch - Google Patents

Abstract

A new type of three-terminal tact switch replaces the traditional two-terminal type. A matrix keyboard is often used when there are many buttons. The detection of the matrix keyboard composed of traditional tact switches is complicated and it is inconvenient to complete the keyboard detection by means of interruption. The present invention designs a novel three-terminal tact switch and provides a connection method and a detection method of a 4*4 matrix keyboard, and the connection method and detection method of a matrix keyboard with m rows and n columns are also included in the claims In detail, the detection of the matrix keyboard composed of this kind of tact switch becomes very simple, and the pressed key can be obtained directly by reading the level state of the row line and column line, and the single-chip microcomputer only needs to pass an interrupt source and Several ordinary IO ports are connected to the matrix keyboard to complete the detection of the matrix keyboard in an interrupted manner. Since the single-chip microcomputer detects the matrix keyboard in an interrupted manner, the single-chip microcomputer can work in a low-power sleep mode and wake it up when a key is pressed. , which helps reduce system power consumption.

Description

A new type of three-terminal tact switch

technical field

The invention relates to a circuit tact switch. The detection of the matrix keyboard formed by the tact switch becomes very simple. In addition, the single-chip microcomputer only needs to be connected to the matrix keyboard through an interrupt source and several common IO ports. The method of interruption completes the detection of the matrix keyboard.

Background technique

The keyboard is the most basic and common input device of the microcomputer system, and the general keyboard is composed of a plurality of tact switches. According to the arrangement of tact switches, keyboards can be divided into linear keyboards and matrix keyboards. In the case of many buttons, we often use a matrix keyboard. The matrix keyboard arranges the tact switches into n rows and m columns. *m tactile switches. The traditional tact switch is a two-terminal type. When we press the switch, the two ends are turned on. In the natural state, the two ends are open and non-conductive. The key translation method of the matrix keyboard composed of light touch switches at both ends often includes the row scanning method and the line inversion method. In the row scanning method, the row scanning method needs to set the level on the row line of the matrix keyboard in sequence, and then Read the value of the port to get the code of the pressed button. This detection method is cumbersome in program and not simple enough. It takes several steps to identify the pressed tact switch. In addition, these methods require the processor to scan and detect the keys in an inquiring manner, which requires the processor to continuously read the level status of the IO. The working mode detection button will cause the CPU to fail to work in the low power mode, which will increase the power consumption of the entire system. If you want to detect the matrix keyboard by means of interrupt, you need to connect the row (column) line to the IO port with interrupt capability, and for some low-end processors, there are few external interrupt resources, which cannot provide enough interrupt capability. Capable IO port. The matrix keyboard composed of traditional two-end tact switches has these two major disadvantages: the detection is not simple enough and cannot work to complete the detection in an interrupted working mode. These two shortcomings are determined by the characteristics of the traditional two-terminal tact switch. In order to overcome these shortcomings, the present invention proposes a new idea from the structure of the tact switch.

Contents of the invention

In order to simplify the detection of the matrix keyboard, and make the single-chip microcomputer only need to connect with the matrix keyboard through an interrupt source and several common IO ports, the detection of the matrix keyboard can be completed in an interrupt mode.

The technical solution adopted in the present invention is: a new type of three-terminal tact switch, which is characterized in that: it is composed of three contact terminals. In the natural state, two of these three terminals are open. Two short circuits.

Keyboard connection method: the three terminals of the three-terminal tact switch are the same, for the convenience of expression, the three terminals of the three-terminal tact switch are respectively numbered as 0, 1, 2, and for m*n tact switches, the It is arranged in m rows and n columns, and the 1 terminals of n three-terminal tact switches in each row are connected by row lines, each row is respectively marked as ROW_1~ROW_m, and the 0 terminals of m three-terminal tact switches in each column are connected by column lines , each column is marked as LINE_1~LINE_n, all m*n tact switches are connected together and marked as COM terminal, and all three-terminal tact switches constitute a matrix keyboard with m rows and n columns.

Query working mode: the row lines ROW_1~ROW_m are respectively connected to the IO ports of the MCU, the column lines LINE_1~LINE_n are respectively connected to the IO ports of the MCU, and the COM terminal is grounded; the MCU obtains the row line and column by reading the value of the IO port connected to the matrix keyboard The level state on the line, each button is pressed corresponds to a level state on the unique row line and column line, so the single-chip microcomputer can read the level state on the row line and column line to identify the Press the button, which realizes the detection of the entire matrix keyboard by the single-chip microcomputer in the working mode of query.

Interrupt working mode 1: Row lines ROW_1~ROW_m are respectively connected to the IO port of the microcontroller, column lines LINE_1~LINE_n are respectively connected to the IO port of the microcontroller, and the COM terminal is connected to the external interrupt pin of the microcontroller, and then the entire Matrix keyboard, set the external interrupt as falling edge trigger, set the IO port connected to the row line and column line as push-pull output mode and output low level, so that as long as any key is pressed, the COM terminal level will be It will be pulled low, the interrupt is triggered, and it enters the interrupt service program. In the interrupt service program, first set the interrupt pin to output mode and output low level, and then set the IO port connected to the row line and column line as a pull-up input mode, the MCU reads the value of the row line and column line, and can identify the pressed button by reading the level state of the row line and column line, wait for the button to be released, and then set the external interrupt as a falling edge trigger after the identification is completed , the IO ports connected to the row line and column line are set to push-pull output mode and all output low level, the single-chip microcomputer continues to wait for the interrupt, which realizes the detection of the entire matrix keyboard by the single-chip microcomputer in the interrupt working mode.

Interrupt working mode 2: the row lines ROW_1~ROW_m are respectively connected to the IO ports of the microcontroller, the column lines LINE_1~LINE_n are respectively connected to the IO ports of the microcontroller, each row line and each column line are respectively connected to a resistor, and the other ends of all resistors Connect to high level; all row lines or all column lines or all row lines and column lines are connected to the input terminal of an AND gate circuit, and the output terminal of the AND gate circuit is connected to the external interrupt pin of the microcontroller, and the external interrupt is set to Falling edge trigger; connect the COM terminal to low level; when any button is pressed, the level of one of the row lines and one of the column lines is pulled low, and the output terminal of the AND gate circuit outputs a low level, and the interrupt triggers , enter the interrupt service program, in the interrupt service program, utilize the interrupt service program to read the position of the key input.

The beneficial effects of the present invention are: the detection of the matrix keyboard formed by the light touch switch of this structure becomes as simple as the linear keyboard, and the single-chip microcomputer only needs to be connected with the matrix keyboard through an interrupt source and several common IO ports to interrupt The way to complete the matrix keyboard detection. Detecting the matrix keyboard with an interrupt not only improves the real-time performance of the entire microcontroller system, improves efficiency, but also allows the system to work in sleep mode, triggering an interrupt to wake up the CPU when a button is pressed, which also reduces the power consumption of the system , save energy, and at the same time extend the life of the keyboard.

Description of drawings

Schematic diagram 1 is the basic structure of the three-terminal tact switch, which has three terminals 0, 1, and 2, and each terminal leads to a pin;

Schematic diagram 2 shows a connection method of a 4*4 matrix keyboard composed of traditional tact switches at both ends;

Schematic Figure 3 shows a connection method for a 4*4 matrix keyboard composed of a new type of three-terminal tact switch to work in query mode;

Schematic Figure 4 shows a connection method in which a 4*4 matrix keyboard composed of a new type of three-terminal tact switch works in an interrupt mode.

Detailed ways

Schematic diagram 2 shows a connection method of a 4*4 matrix keyboard composed of traditional tact switches at both ends and a method for realizing keyboard detection. ^3 (indicates the 0~3 bits of the P1 port, and some textbooks or programming languages express it as P1.0~P1.3, and the representation method here is also one of the common marking symbols, the same below; at the same time, there are The port is a bidirectional port, or called a quasi-bidirectional port, which can output information and input information. Here, P1 has the function of a bidirectional port) to connect and set P1^0~P1^3 to push-pull output mode. Lines LINE_1~LINE_4 are respectively connected to P1^4~P1^7 of the single chip microcomputer and set P1^4~P1^7 to the pull-up input mode (the pin is high level when it is suspended), and the line scanning method is used to detect the matrix keyboard. Set P1^0~P1^3 separately to low level, every time the low level is set, P1^4~P1^7 must be read to detect the state of each column line to determine which button is pressed (because the single chip microcomputer The scanning speed is far faster than the human input speed. Now the frequency of the single-chip microcomputer can reach 300MHz. Assuming that the scanning needs 100 cycles, it is about the order of microseconds, and the human input speed is on the order of 0.1 seconds. Therefore, compared to the human input speed, the time required for scanning can be ignored). Specific implementation plan: firstly, P1^0 outputs low level, and the remaining three lines (P1^1, P1^2, P1^3) are set to high level. At this time, the state of the first row of buttons can be detected. If key1 If key2 is pressed, the level of LINE_3 will be pulled down, and the other lines will be high, and so on for key3 and key4. The state of the first row of keys can be obtained by reading the state of the level of the column line. Then detect the buttons on the second row, output P1^1 to low level, and set the remaining three rows (P1^0, P1^2, P1^3) to high level, then you can detect the status of the second row of buttons , if key5 is pressed, the level of LINE_4 is pulled low, and the rest of the column lines are high. If key6 is pressed, the level of LINE_3 is pulled low, and the rest of the column lines are high, and so on key8, so that the state of the second row of keys can be obtained by reading the state of the level of the column line. In the same way, the levels of P1^2 and P1^3 are set low in turn, and the remaining column lines are high, so that the states of the buttons in the third row and the fourth row can be detected respectively. In this way, the entire matrix keyboard is detected by the row scanning method. Since it is composed of traditional tact switches at both ends, this 4*4 matrix keyboard is mostly detected through the query method (the single-chip microcomputer needs to continuously read the levels of the row lines and column lines), and it can be seen that the detection process is relatively Complex and cumbersome.

Next, a connection method of a 4*4 matrix keyboard composed of the three-terminal tact switch described in the present invention and a method for realizing keyboard detection are given.

Firstly, the method of keyboard detection by query is given: according to the schematic diagram 3, the row lines ROW_1~ROW_4 are respectively connected to the single-chip microcomputer P1^0~P1^3, and the column lines LINE_1~LINE_4 are respectively connected to the single-chip microcomputer P1^4~P1^7 , the COM terminal is connected to the power ground (low level). P1^0~P1^7 are all set to pull-up input mode. The single-chip microcomputer only needs to continuously read the value of P1^0~P1^7, that is, the entire port of P1, to obtain the status of the entire matrix keyboard. When the button S1 is pressed, the row line and column line connected to S1 are connected to the COM terminal, and are pulled to a low level, that is, the levels of P1^0 and P1^7 are both 0, and the P1 port is read at this time The value is 0x7e (0x indicates hexadecimal, 0x7e in hexadecimal indicates binary 01111110), P1^0~P1^7 correspond to the low to high bits of a byte in turn, if S16 is pressed, the line connected to S16 The line and column lines are both connected to the COM terminal, and are pulled to a low level, that is, the levels of P1^3 and P1^4 are both 0. At this time, the value of the P1 port is read as 0xe7 (binary 11100111), and the button is pressed in the same way. When S1~S16 is pressed, the corresponding P1 port values are {0x7e, 0xbe, 0xde, 0xee, 0x7d, 0xbd, 0xdd, 0xed, 0x7b, 0xbb, 0xdb, 0xeb, 0x77, 0xb7, 0xd7, 0xe7}, In this way, it is only necessary to continuously read the value of the P1 port to obtain the code of the pressed button and then obtain the number of the pressed button. Compared with the detection of the traditional two-stage tact switch matrix keyboard described above, it is necessary to lower the row lines in turn and then read the value of P1^4~P1^7 to scan and detect the keys of each row. The detection of the 4*4 matrix keyboard composed of touch switches is greatly simplified, and the entire matrix keyboard can be detected directly by reading the value of the P1 port.

In addition to simplifying the detection of the matrix keyboard, the matrix keyboard composed of three-terminal tact switches can also easily complete its detection in an interrupted working mode. Next, the method of realizing keyboard detection by means of interrupt is given: According to the schematic diagram 4, the row lines ROW_1~ROW_4 are respectively connected to the single-chip microcomputer P1^0~P1^3, and the column lines LINE_1~LINE_4 are respectively connected to the single-chip microcomputer P1^4~P1^7 Connect the COM terminal to the external interrupt pin of the microcontroller, set the external interrupt to be triggered by the falling edge, set the P1 port to the push-pull output mode and output all low levels, so that as long as any button is pressed, the COM The terminal level will be pulled low, the interrupt is triggered, and the interrupt service program is entered. In the interrupt service program, first set the interrupt pin to output mode and output low level, set the P1 port to pull-up input mode, and the microcontroller reads again. Take the value of the P1 port, and by reading the value of the P1 port, you can get the code of the pressed button and then the number of the pressed button. When the buttons S1~S16 are pressed, the corresponding P1 port value is {0x7e ,0xbe,0xde,0xee,0x7d,0xbd,0xdd,0xed,0x7b,0xbb,

0xdb, 0xeb, 0x77, 0xb7, 0xd7, 0xe7}, after getting the number of the pressed button, set the P1 port to the output mode and output a low level, set the external interrupt to the input mode, and exit the interrupt. In this way, the microcontroller It can work in low-power sleep mode and wake it up when a key is pressed.

Claims (5)

1. novel three end touch-switchs, is characterized in that: be made up of three contact jaws, and under state of nature, these three ends are opened a way between two, when pressing switch, hold short circuit between two for these three.

2. the novel three end touch-switchs of one according to claim 1, it is characterized in that: three ends of three end touch-switchs are identical, for ease of statement, three of three end touch-switchs ends are numbered 0 respectively, 1, 2, for m*n touch-switch, be arranged in the capable n row of m, 1 end of every a line n three end touch-switchs is connected by line, each row is designated as ROW_1 ~ ROW_m respectively, 0 end of m three end touch-switchs of each row is connected by alignment, each row are designated as LINE_1 ~ LINE_n respectively, 2 ends of all m*n touch-switch connect together and are designated as COM end, all three end touch-switchs constitute the matrix keyboard of the capable n row of m.

3. the novel three end touch-switchs of one according to claim 2, is characterized in that: line ROW_1 ~ ROW_m is connected with single-chip I/O mouth respectively, and alignment LINE_1 ~ LINE_n is connected with single-chip I/O mouth respectively, and COM holds ground connection; The value of the I/O port that single-chip microcomputer is connected by reading matrix keyboard obtains the level state on line and alignment, each button is pressed a level state on corresponding unique line and alignment, so the level state that just can be read on line and alignment by single-chip microcomputer identifies the button be pressed, which achieves single-chip microcomputer and detect whole matrix keyboard with the working method of inquiry.

4. the novel three end touch-switchs of one according to claim 2, it is characterized in that: line ROW_1 ~ ROW_m is connected with single-chip I/O mouth respectively, alignment LINE_1 ~ LINE_n is connected with single-chip I/O mouth respectively, COM end is received the external interrupt pin of single-chip microcomputer, next whole matrix keyboard is detected in the mode of interrupting, external interrupt is set to negative edge trigger, the I/O port be connected with line alignment is set to recommend output mode and whole output low level, like this, as long as there is any one button to be pressed, COM holds level just to be dragged down, down trigger, enter interrupt service routine, in interrupt service routine, first interrupt pin is set to output mode and output low level, again the I/O port be connected with line alignment is set to pull-up input pattern, the value of single-chip microcomputer read line alignment line again, just the button be pressed can be identified by the level state of read line alignment line, wait button discharges, again external interrupt is set to negative edge after identification completes trigger, the I/O port be connected with line alignment is set to recommend output mode and whole output low level, the arriving that single-chip microcomputer continuation etc. are to be interrupted, which achieves single-chip microcomputer and detect whole matrix keyboard with the working method of interrupting.

5. the novel three end touch-switchs of one according to claim 2, it is characterized in that: line ROW_1 ~ ROW_m is connected with single-chip I/O mouth respectively, alignment LINE_1 ~ LINE_n is connected with single-chip I/O mouth respectively, every root line is connected a resistance all respectively with every root alignment, and the other end of all resistance is connected to high level; All lines or all alignments or all lines and alignment are connected to the input end of an AND circuit, and the output terminal of AND circuit is connected to the external interrupt pin of single-chip microcomputer, external interrupt is set to negative edge and triggers; COM end is received low level; Any one button is pressed, and wherein the level of a line and an alignment is dragged down, and AND circuit output terminal exports a low level, down trigger, enter interrupt service routine, in interrupt service routine, utilize interrupt service routine to read the position of the key of input.