Key scanning circuit

Button scanning circuit

The invention provides a button circuit, in particular a button circuit capable of determining the position of a button according to the length of the discharge time.

Please refer to Figure 1. FIG. 1 is a schematic diagram of a conventional button circuit 10. The button circuit 10 includes m driving lines A, B, C..., M for inputting a scanning pulse wave, n output lines a, b, c, ..., n for outputting the scanning pulse wave, and m* The n keys Aa, Ab, ..., Mn are arranged in a matrix, wherein m driving lines are alternately input with a scanning pulse wave. If the scan pulse is input to the drive line B, and the button Bb is pressed, that is, the button Bb is turned on, the current flows from the drive line B to the button Bb and then to the output line b, so that the output line b is output. The pulse signal (as indicated by the solid line 12) is known to be pressed by the button Bb.

However, if the scan pulse is input to the drive line B, the button Bb, the button Cb and the button Cd are simultaneously pressed, and in addition to the output of the output line b, the current will also follow the slave drive line. B flows to the button Bb and then flows to the output line b and then flows to the button Cb and then flows to the driving line C and then flows to the button Cd and then to the output line d (as indicated by the broken line 14), so that the output line d has a pulse wave signal. Output, so you will get the result of the Bd button being pressed, but it is not. So this produces a fake code called the "ghost key" or "phantom key". In addition to this drawback, the m drive lines and n output lines of the keyboard circuit 10 must occupy m+n turns of the processor, which is not very economical.

In addition, in U.S. Patent No. 5,619,169, a button circuit design using a transmission line is proposed, in which a plurality of resistors of the same resistance value are connected in series, and a capacitor is connected in series. When the button is pressed, the capacitor is discharged through the series resistor grounding, and the discharge is consumed by the detector. Time to calculate the resistance value, you know which key is pressed. However, in this U.S. patent, the button can only perform one discharge operation at each press, so it is easy to generate an error, and only one key can be detected at a time, and cannot be applied to two or more keys at the same time. The situation.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a key circuit capable of determining a button position in accordance with a discharge time during a single pressing and determining the position of a button in accordance with the length of the discharge time to solve the above problem.

Please refer to Figure 2 to Figure 3. 2 is an external view of a key pad 40 of a remote controller. FIG. 3 is a schematic diagram of the button circuit 50 of the present invention. The button circuit 50 of the present invention can be an encoding or decoding circuit of a key pad 40 (Fig. 3) of a remote controller. The keypad 41 includes a housing 42 and a plurality of buttons 44 are detachably disposed on the housing 42. The button circuit 50 includes a control unit 52, a first charge storage circuit 54, a second charge storage circuit 56, and a button matrix circuit 58 under the button 44.

The control unit 52 includes a processor 66 having a control terminal 60 and two detection terminals 62, 64, and two voltage sensors 68, 70.

The first charge storage circuit 54 has a charge and discharge terminal 72 coupled to the detection terminal 62 of the control unit 52 via a voltage sensor 68. The second charge storage circuit 56 also has a charge and discharge terminal 74 coupled to the other detection terminal 64 of the control unit 52 via the voltage sensor 70.

The key matrix circuit 58 includes a plurality of resistors 76 each having a first end and a second end, and a plurality of manual switches 78 each having a first end and a second end. The plurality of resistors 76 individually form a series resistor circuit having a first end 80 and a second end 82 in such a manner that the first end thereof is in contact with the second end of the adjacent resistor. The first end 80 of the series resistor circuit is coupled to the charge and discharge terminal 72 of the first charge storage circuit 54. The first charge storage circuit 54 includes a capacitor, and the first end 80 of the series resistor circuit is connected in series to form an RC circuit. The second terminal 82 of the resistor circuit is coupled to the charge and discharge terminal 74 of the second charge storage circuit 56. The second charge storage circuit 56 also includes a capacitor in series with the second terminal 82 of the series resistor circuit to form another RC circuit. The first ends of the plurality of switches 78 are respectively coupled to the junctions of the two resistors 76, and the second ends of the plurality of switches 78 are coupled to the control terminals 60 of the control unit 52.

In the control unit 52. The control terminal 60 can control the jump between the grounded or floating state. The voltage sensors 68, 70 are respectively connected to the first end 80 and the second end 82 of the series resistance circuit for measuring the discharge voltages of the first end 80 and the second end 82 of the series resistance circuit. The processor 66 includes a first conversion table 84 for storing a discharge time comparison value of the resistance between the adjacent contacts 76 and the first terminal 80 of the series resistance circuit, and a second conversion table 86. The memory has a discharge time comparison value of the resistance between the adjacent points of the adjacent resistors 76 to the second end 82 of the series resistor circuit.

When a button 44 is pressed, a corresponding switch 78 is actuated to be pressed against one of the adjacent resistors 76, and then the control terminal 60 is grounded (the processor 66 controls the control terminal 60). Will jump between the ground and the floating, and the processor 66 starts counting when the control terminal 60 starts to ground), at this time, the charge stored in the first charge storage circuit 54 starts to discharge, and the phase contact to the series resistance circuit The value of the resistance between one end 80 determines the discharge time of the RC circuit. The voltage drops when discharging, and when the voltage of the first terminal 80 of the series resistance circuit drops below a predetermined voltage value, the voltage sensor 68 is turned on, and the first detecting end 62 is raised by the low level. To the high level, as detected by the processor 66, the processor 66 calculates the length of time from when the RC circuit begins to discharge until the voltage sensor 68 is turned on (correctly, the control terminal 60 begins to ground to the detect The measuring terminal 62 detects the length of the high level on time. Finally, the processor 66 determines the corresponding position of the activated switch 78 according to the first conversion table 84 according to the length of time, and outputs a correct button signal.

Similarly, when the control terminal 60 is grounded, the charge stored in the second charge storage circuit 56 also begins to discharge, and the resistance value of the pressed contact point to the second end 82 of the series resistance circuit determines the value. Discharge time of the RC circuit. The voltage drops when discharging, and when the voltage of the second end 82 of the series resistance circuit drops below a predetermined voltage value, the voltage sensor 70 is turned on, and the second detecting end 64 is detected. To the high level, similarly, the processor 66 calculates the length of time that the RC circuit begins to discharge until the voltage sensor 70 is turned on (correctly, when the control terminal 60 starts to ground until the detection terminal 64 is detected high). According to the length of time, the final processor 66 determines the corresponding position of the activated switch 78 according to the second conversion table 86, and outputs a correct button signal.

When the control terminal 60 is floating, the first charge storage circuit 54 and the second charge storage circuit 56 re-store the charge.

Therefore, when a button 44 is pressed, that is, when a switch 78 is turned on, the first detecting end 62 and the second detecting end 64 are detected to change the level, so that the first and second conversion tables are respectively performed. 84, 86 get the same button signal. When two buttons 44 are pressed at the same time, two switches 78 are turned on, and the two buttons 44 are detected by the first and second detecting ends 62, 64, respectively, and then according to the first and second. The conversion tables 84, 86 get two button signals. When a plurality of buttons 44 are pressed, the button signals of the two buttons 44 on the button circuit 50 closest to the first end 80 and the second end 82 of the series resistor circuit are obtained.

Please refer to FIG. 4, which is a schematic diagram of the relationship between the pressing time of the button and the charging and discharging time. In this embodiment, each of the resistance values of the series resistors between the different keys is 50 Ω, the capacitance value of the capacitor is 1 μF, and then the voltage value of the voltage Vcc is 5 V, and the relationship of the discharge time of the capacitor is applied.<img file="TW439366B_D0001.tif" />, you get, the unit is μs, very short. The charging time is determined by the capacitance value and the resistance value between the voltage terminals. Here, the resistance value is 100KΩ, so the charging time is about 500μs. The processor 66 controls the control terminal 60 to have a key scan period between ground and floating for about 2 ms. Of course, each floating time is greater than 500 μs to allow the charging to be full. Because the present invention begins to calculate the RC circuit discharge time when the control terminal 60 starts to ground, the first button signal may be wrong, and it may be obtained that the control terminal 60 has been grounded and the button is pressed after the calculation time is started. Therefore, the grounding time is not the same as the time when the RC circuit starts to discharge. Therefore, the incorrect RC circuit discharge time is obtained, and the wrong button signal is obtained, but according to the experiment, each button is pressed for the fastest time, 100 ms, during this period, according to In the design of this embodiment, the processor 66 can actually scan the button many times, so although the first signal can be wrong, but because there will still be a lot of correct button signal output, the correct output can be taken later. Or averaging to reduce the error, that is, designing the processor 66 to receive the output of several key signals to actually display a key signal. So in fact, it is not a problem to quickly press and press.

The first charge storage circuit 54 and the second charge storage circuit 56 are simultaneously disposed at both ends of the series resistance circuit, so that the two buttons can be detected at the same time, and if only one button is pressed at a time, In this case, only one of the first charge storage circuit 54 and the second charge storage circuit 56 may be disposed at one end of the series resistance circuit. And the resistor 76 shown therein may, of course, be printed directly on the thin film circuit board and the equivalent resistance of the printed material.

Please refer to Figure 5 and Figure 6. Figure 5 is a view of a computer keyboard 90. Figure 6 is a diagram of a key circuit 100 in accordance with another embodiment of the present invention. The computer keyboard 90 includes a housing 92 and three sets of buttons 94, 96, 98 that are pressably disposed on the housing 92. The button circuit 100 of the present invention is used, and each set of buttons 94, 96, 98 is provided. There is a button matrix circuit 110, 120, 130 and two charge storage circuits 112, 114, 122, 124, 132, 134. Each group of buttons can accept the pressing of two buttons at a time, so that a total of six buttons can be detected at a time, which can handle most occasions where multiple buttons need to be pressed at the same time, for example, hot boot The key should press the three keys ctrl, alt and del at the same time. At this time, the ctrl key and the alt key can be placed in the same group of buttons, for example, the button group 94, and then the de1 button is placed in another group button, for example, the button group. 98. You can use the hot power button. Each button group requires only three turns of the processor 140, so the keyboard 100 requires only nine turns in total.

In summary, the key circuits 50 and 100 of the present invention do not have the problem of generating a false word, a "ghost key", and require fewer processors than the conventional circuit 10. Conventional keyboard circuit 10 requires a set of m*n matrix keys to require m+n port. Now, no matter how many keys, you can use only three port, or more into several groups, for example, three groups are used and then nine port are used. .

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be covered by the present invention.

<p>52 control unit 54 first charge storage circuit</p><p>56 second charge storage circuit 58 button matrix circuit</p><p>60 control terminal 62, 64 detection terminal</p><p>66 processor 68 , 70 voltage sensor</p><p>72, 74 charge and discharge end 76 resistor</p><p>78 switch 80 series resistance circuit first end</p><p>82 series resistance circuit second end 84 first conversion table</p><p>86 second conversion table</p>

The first figure is a schematic diagram of a conventional button circuit.

The second picture is a view of the keypad of the remote control.

The third figure is a schematic diagram of the button circuit of the present invention.

The fourth figure is a schematic diagram of the relationship between the pressing time of the button and the charging and discharging time.

The fifth picture is a view of a computer keyboard.

The sixth figure is another embodiment of the button circuit of the present invention.