CN113595558A - Multi-key judgment system based on LCD pin multiplexing - Google Patents
Multi-key judgment system based on LCD pin multiplexing Download PDFInfo
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- CN113595558A CN113595558A CN202111162241.2A CN202111162241A CN113595558A CN 113595558 A CN113595558 A CN 113595558A CN 202111162241 A CN202111162241 A CN 202111162241A CN 113595558 A CN113595558 A CN 113595558A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
- H03M11/00—Coding in connection with keyboards or like devices, i.e. coding of the position of operated keys
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Abstract
The invention provides a multi-key judgment system based on LCD pin multiplexing, which relates to the technical field of multi-key judgment, and is characterized in that two keys are connected between a first I/O (input/output) pipe orifice and a plurality of SEG/COM (field emission gate) ports, and different output levels are configured for the SEG/COM ports connected with the keys, so that two Schmitt triggers with different high and low level thresholds arranged in the first I/O ports simultaneously receive input signals of the first I/O ports, and judge the pressed keys according to the output of the two Schmitt triggers under different level signals, thereby realizing the simultaneous judgment of two key states. And the invention has the advantage of less key I/O resource occupation by LCD pin multiplexing.
Description
Technical Field
The invention relates to the technical field of multi-key judgment, in particular to a multi-key judgment system based on LCD pin multiplexing.
Background
The micro control unit MCU widely used in various fields has the function of processing input signals and then outputting the processed signals, the key as a general external input device can be connected with an I/O port of the micro control unit MCU to provide corresponding external input signals for the micro control unit MCU, the system formed by the key and the micro control unit MCU has various human-computer interaction functions and is widely applied to various daily life applications, if the liquid crystal LCD is applied to the system, a new system with more abundant functions can be formed, and in the new system, the liquid crystal LCD is connected with the micro control unit MCU as an external output device and correspondingly displays according to the output signals.
However, in a system composed of a liquid crystal LCD, a key and a micro control unit MCU, the micro control unit MCU needs to occupy more I/O ports for controlling the display of the liquid crystal LCD, and the micro control unit MCU has limited I/O resources, so that the situation of insufficient I/O resources of the key is often encountered.
In order to solve the technical problem of insufficient I/O resources of the keys, it is urgently needed to provide a system having a Liquid Crystal Display (LCD) function and capable of implementing multiple key judgment inputs.
Disclosure of Invention
The present invention is directed to solve the above mentioned problems in the background art, and to provide a multi-key judgment system based on LCD pin multiplexing.
In order to achieve the above object, the present invention provides a multi-key judgment system based on LCD pin multiplexing, comprising: the micro control unit MCU is provided with two Schmitt triggers with different high and low level thresholds in a first I/O port to receive an input signal of the first I/O port, so that a pressed key is judged according to the output of the two Schmitt triggers under different level signals, wherein the high level threshold of the first Schmitt trigger is greater than a V0 level and less than a V1 level, the low level threshold of the second Schmitt trigger is greater than a V1 level and less than a V2 level, and the high level threshold of the second Schmitt trigger is greater than a V1 level and less than a V2 level;
the liquid crystal LCD is connected with a plurality of SEG/COM ports of the micro control unit MCU and adopts four segments of level input of V0-V3;
and the first end of each key is connected with different SEG/COM ports, the second end of each key is connected with the first I/O port, and the SEG/COM ports connected with the keys are configured to output different levels.
Optionally, the SEG/COM port connected to the first key is configured to output a V1 level, and the SEG/COM port connected to the second key is configured to output a V2 level.
Optionally, the first schmitt trigger output flag is a keyflag [0], the second schmitt trigger output flag is a keyflag [1], and when the keyflag [1] =0 and the keyflag [0] =0 are detected, it can be determined that the first key is pressed; when keyflag [1] =0 and keyflag [1] =1 are detected, the second key can be judged to be pressed; when keyflag [1] =1 and keyflag [1] =1 are detected, it may be determined that no key has been pressed.
Optionally, the first I/O port adopts a pull-down resistance input mode.
Optionally, the SEG/COM port connected to the first key is configured to output a V0 level, and the SEG/COM port connected to the second key is configured to output a V1 level.
Optionally, the first schmitt trigger output flag is a keyflag [0], the second schmitt trigger output flag is a keyflag [1], and when the keyflag [1] =0 and the keyflag [0] =1 are detected, it can be determined that the first key is pressed; when keyflag [1] =0 and keyflag [1] =1 are detected, the second key can be judged to be pressed; when keyflag [1] =0 and keyflag [1] =0 are detected, it may be determined that no key has been pressed.
Optionally, the first I/O port adopts a pull-up resistance input mode.
Optionally, the low level threshold of the first schmitt trigger is 0.6V, the high level threshold of the first schmitt trigger is 0.9V, the low level threshold of the second schmitt trigger is 1.2V, and the high level threshold of the second schmitt trigger is 1.8V.
The invention has the beneficial effects that:
the multi-key judgment system based on LCD pin multiplexing provided by the embodiment of the invention connects two keys between a first I/O port and a plurality of SEG/COM ports, configures different output levels for the SEG/COM ports connected with the keys, so that two Schmitt triggers with different high and low level thresholds arranged in the first I/O port simultaneously receive input signals of the first I/O port, and judges the pressed keys according to the outputs of the two Schmitt triggers under different level signals, thereby realizing the simultaneous judgment of two key states. The method has the advantage of less occupied key I/O resources.
The features and advantages of the present invention will be described in detail by embodiments in conjunction with the accompanying drawings.
Drawings
FIG. 1 is a schematic circuit diagram of a multi-key judgment system based on LCD pin multiplexing according to an embodiment of the present invention;
FIG. 2 is one of the schematic diagrams of the internal circuit of the P1 pin according to the embodiment of the present invention;
FIG. 3 is a block diagram illustrating the setting of the output level of the SEG/COM port according to the embodiment of the present invention;
fig. 4 is a second schematic diagram of the internal circuit of the P1 pin according to the embodiment of the present invention.
In the figure: 101-pull-down control register, 102-data output register, 103-output enable controller, 104-pull-down resistor, 105-pull-up enable register, 106-inverter, 107-pull-up resistor.
Detailed Description
The present invention will be described in further detail below with reference to specific examples in order to facilitate understanding by those skilled in the art.
The embodiment of the invention provides a multi-key judgment system based on LCD pin multiplexing.
Referring to fig. 1, a multi-key determination system based on LCD pin multiplexing according to an embodiment of the present invention includes the following structures:
the P1 pin of the MCU is a first I/O port, and two Schmitt triggers with different high and low level thresholds are arranged in the first I/O port to receive input signals of the first I/O port, so that the pressed key is judged according to the output of the two Schmitt triggers under different level signals. Referring to fig. 2, which is a schematic diagram of an internal circuit of the P1 pin, two schmitt triggers with different high and low level thresholds are disposed inside the first I/O port to receive an input signal of the first I/O port, so as to determine a pressed key according to outputs of the two schmitt triggers under different level input signals, and the high level threshold of the first schmitt trigger SMIT1 is smaller than the low level threshold of the second schmitt trigger SMIT 2. In other embodiments, when the number of the keys is three or four, on the basis of the original hardware structure of fig. 2, only the third schmitt trigger SMIT3 or the fourth schmitt trigger SMIT4 needs to be added, and details are not described herein.
And the liquid crystal LCD is connected with a plurality of SEG/COM ports of the micro control unit MCU and adopts four-segment level input of V0-V3. Because the liquid crystal LCD adopts four-segment level input, the SEG/COM port can output 4 different levels at most, and 3 keys can be judged at most simultaneously.
In the case that 2 or 3 keys need to be judged, the liquid crystal LCD can select four-segment level input of V0-V3, wherein V0=0V, V1=1/3VDD, V2=2/3VDD and V3= VDD. In addition, the liquid crystal LCD can select five levels from V0-V4 for inputting when 4 keys need to be judged.
And the first end of each key is connected with different SEG/COM ports, the second end of each key is connected with the first I/O port, and the SEG/COM ports connected with the keys are configured to output different levels. In this embodiment, when the number of the KEYs is two, the first end of the first KEY1 is connected to the P2 pin, the first end of the second KEY2 is connected to the P3 pin, the second end of the first KEY1 and the second end of the second KEY2 are both connected to the P1 pin, where the P2 and the P3 pins are multiplexing pins that can be used as both SEG ports and general I/O ports, and the first end of the first KEY1 and the first end of the second KEY2 can be connected to other COM ports or SEG ports, respectively.
In other embodiments, when the number of the KEYs is three or four, the first ends of the third KEY3 and the fourth KEY4 are respectively connected to other COM ports or SEG ports, and the second ends of the third KEY3 and the fourth KEY4 are both connected to the P1 pin.
Because the number of the keys is two, the corresponding outputs of the two schmitt triggers under two different input levels are judged, and the schmitt trigger has the advantages of good practicability, low complexity and the like in the practical application process, the number of the keys is preferably two in the embodiment.
In other embodiments, the three keys may be simultaneously determined according to the corresponding outputs of the three schmitt triggers at three different input levels, or the four keys may be simultaneously determined according to the corresponding outputs of the four schmitt triggers at four different input levels.
When the multi-key judgment system based on LCD pin multiplexing judges the keys, the output level of the SEG/COM port needs to be set according to the number of the keys in the system. Specifically, when the number of the keys needs to be judged to be two, different output levels need to be set for the two SEG/COM ports; when the number of the keys needs to be judged to be three or four, different output levels need to be set for three or four SEG/COM ports.
Specifically, the setting can be performed through the output selection module, please refer to fig. 3, which is a block diagram for setting the output LEVEL of the SEG/COM port when the number of the keys is two or three, and since it is necessary to determine that the number of the keys is three at most, four LEVELs of V0 to V3 can be selected for input, and the output LEVEL is selected by changing the LEVEL input. When LEVEL input is 00, the output LEVEL of the SEG/COM port is V0; when LEVEL input is 01, the output LEVEL of the SEG/COM port is V1; when LEVEL input is 10, the output LEVEL of the SEG/COM port is V2; when the LEVEL input is 11, the output LEVEL of the SEG/COM port is V3, so that the setting of the output LEVEL of the SEG/COM port is realized. In addition, when the number of the keys is four, the four-stage level input can be referred to for the corresponding setting of the five-stage level input of V0-V4, and thus the description is omitted here.
In this embodiment, the number of the keys in the system is two, the number of the SEG/COM ports to be set is 2, and there are 3 kinds of levels that can be allocated, so there are 3 kinds of schemes, only two of the schemes are specifically described here, and the principle of the third scheme is the same as that of the first two schemes, so further description is omitted here.
In the first scheme, the SEG/COM port connected to the first KEY1 is configured to output a V1 level, and the SEG/COM port connected to the second KEY2 is configured to output a V2 level.
In the second scheme, the SEG/COM port connected to the first KEY1 is configured to output a V0 level, and the SEG/COM port connected to the second KEY2 is configured to output a V1 level.
Accordingly, in order to ensure that the V0 level signal can be recognized as a low level by the first schmitt trigger and the V1 level signal can be recognized as a high level by the first schmitt trigger, the high level threshold of the first schmitt trigger is set to be greater than the V0 level and less than the V1 level. To ensure that signals below the V1 level can be recognized as low by the second schmitt trigger whose low threshold is greater than the V1 level and less than the V2 level and whose high threshold is greater than the V1 level and less than the V2 level, the V2 level signal can be recognized as high.
In other embodiments, when the number of the keys is three, four different levels need to be allocated to the 3 SEG/COM ports, one level allocation scheme among the four schemes may be selected to set the high and low level thresholds of the first schmitt trigger, the second schmitt trigger, and the third schmitt trigger, and the specific setting principle is the same as that under two keys.
In other embodiments, when four keys are pressed, five different levels need to be allocated to the 4 SEG/COM ports, and setting of high and low level thresholds of the first schmitt trigger, the second schmitt trigger, the third schmitt trigger and the fourth schmitt trigger is performed according to five level allocation schemes, where the specific setting principle is the same as that for the two keys, and as long as output results of the schmitt triggers at different levels do not generate aliasing during key judgment, a person skilled in the art can perform corresponding adjustment, and details are not described herein.
Referring to fig. 1 and 2, in a first embodiment, a pull-down resistor input mode is adopted, an output flag of the first schmitt trigger SMIT1 is keyflag [0], an output flag of the second schmitt trigger SMIT2 is keyflag [1], and when keyflag [1] =0 and keyflag [0] =0 are detected, it can be determined that the first key is pressed; when keyflag [1] =0 and keyflag [1] =1 are detected, the second key can be judged to be pressed; when keyflag [1] =1 and keyflag [1] =1 are detected, it can be judged that no key is pressed, and therefore the state of two keys can be judged at the same time.
Referring to fig. 1 and 4, in a second embodiment, a pull-up resistor input mode is adopted, an output flag of the first schmitt trigger SMIT1 is keyflag [0], an output flag of the second schmitt trigger SMIT2 is keyflag [1], and when keyflag [1] =0 and keyflag [0] =1 are detected, it can be determined that the first key is pressed; when keyflag [1] =0 and keyflag [1] =1 are detected, the second key can be judged to be pressed; when keyflag [1] =0 and keyflag [1] =0 are detected, it can be judged that no key is pressed, and therefore the state of two keys can be judged at the same time.
In addition, the first I/O port is set to be input floating, and the first KEY1 or the second KEY2 is pressed, so that the display of the liquid crystal display cannot be influenced. A voltage of 3V may be employed as VDD, so V0=0V, V1=1V, V2=2V, V3= 3V. Other different VDD are within the scope of the present invention. Under the condition that 3V voltage is adopted as VDD, the low level threshold of the first Schmitt trigger is 0.6V, the high level threshold of the first Schmitt trigger is 0.9V, the low level threshold of the second Schmitt trigger is 1.2V, the high level threshold of the second Schmitt trigger is 1.8V, and the high and low level thresholds of the first Schmitt trigger and the second Schmitt trigger can be correspondingly adjusted according to requirements, so that the method also belongs to the protection range of the invention.
To sum up, in the multi-key judgment system based on LCD pin multiplexing according to an embodiment of the present invention, two keys are connected between a first I/O port and a plurality of SEG/COM ports, and different output levels are configured for the SEG/COM ports connected with the keys, so that two schmitt triggers with different high and low level thresholds in the first I/O port simultaneously receive input signals of the first I/O port, and judge a pressed key according to outputs of the two schmitt triggers under different level signals, thereby realizing simultaneous judgment of two key states, and compared with the prior art, the technical problem that when judging a plurality of key states, an I/O port connected with a key receives zero level, so that only whether a key is pressed but a specific key cannot be judged is solved, and the embodiment of the present invention uses LCD pin multiplexing, the method has the advantage of less occupied key I/O resources.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (8)
1. A multi-key judgment system based on LCD pin multiplexing is characterized by comprising:
the micro control unit MCU is provided with two Schmitt triggers with different high and low level thresholds in a first I/O port to receive an input signal of the first I/O port, so that a pressed key is judged according to the output of the two Schmitt triggers under different level signals, wherein the high level threshold of the first Schmitt trigger is greater than a V0 level and less than a V1 level, the low level threshold of the second Schmitt trigger is greater than a V1 level and less than a V2 level, and the high level threshold of the second Schmitt trigger is greater than a V1 level and less than a V2 level;
the liquid crystal LCD is connected with a plurality of SEG/COM ports of the micro control unit MCU and adopts four segments of level input of V0-V3;
and the first end of each key is connected with different SEG/COM ports, the second end of each key is connected with the first I/O port, and the SEG/COM ports connected with the keys are configured to output different levels.
2. The LCD pin multiplexing-based multi-button decision system of claim 1, wherein the SEG/COM port connected to the first button is configured to output a V1 level, and the SEG/COM port connected to the second button is configured to output a V2 level.
3. The LCD pin multiplexing-based multi-key determination system according to claim 2, wherein the first schmitt trigger output flag is keyflag [0], the second schmitt trigger output flag is keyflag [1], and when keyflag [1] =0 and keyflag [0] =0 are detected, it is determined that the first key is pressed; when keyflag [1] =0 and keyflag [1] =1 are detected, the second key can be judged to be pressed; when keyflag [1] =1 and keyflag [1] =1 are detected, it may be determined that no key has been pressed.
4. The LCD pin multiplexing-based multi-key judgment system of claim 2, wherein the first I/O port adopts a pull-down resistor input mode.
5. The LCD pin multiplexing-based multi-button decision system of claim 1, wherein the SEG/COM port connected to the first button is configured to output a V0 level, and the SEG/COM port connected to the second button is configured to output a V1 level.
6. The LCD pin multiplexing-based multi-key determination system of claim 5, wherein the first Schmitt trigger output flag is keyflag [0], the second Schmitt trigger output flag is keyflag [1], and when keyflag [1] =0 and keyflag [0] =1 are detected, the first key can be determined to be pressed; when keyflag [1] =0 and keyflag [1] =1 are detected, the second key can be judged to be pressed; when keyflag [1] =0 and keyflag [1] =0 are detected, it may be determined that no key has been pressed.
7. The LCD pin multiplexing-based multi-key determination system of claim 5, wherein the first I/O port adopts a pull-up resistor input mode.
8. The LCD pin multiplexing-based multi-key determination system according to claim 1, wherein the low level threshold of the first schmitt trigger is 0.6V, the high level threshold of the first schmitt trigger is 0.9V, the low level threshold of the second schmitt trigger is 1.2V, and the high level threshold of the second schmitt trigger is 1.8V.
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Application publication date: 20211102 |