Key scanning method of key scanning hardware circuit based on carbon film wiring
A scanning method and a technology of carbon film wiring, applied in the field of button scanning circuits, can solve problems such as inapplicability, large resistance value, and large interference of wiring state, so as to reduce production costs, solve the influence of parasitic capacitance, and save silver resources Effect
Active Publication Date: 2016-04-13
SINO WEALTH ELECTRONICS
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Problems solved by technology
[0002] In the existing button scanning circuit, compared with the silver film wiring, the carbon film wiring is cheap but the resistance value is larger (10k ~ 500k)
And because of its large resistance value, a large trace capacitance (5-7pF) is formed between the carbon film traces, so that the state interference between the traces is relatively large
Therefore, the original button scanning method is not applicable to the carbon film wiring button scanning circuit
Method used
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[0061] figure 1 It is a schematic diagram of a key scanning circuit in the prior art. like figure 1 As shown, its status line can be multiple, figure 1 Take 8 items as an example. R00~R07 is the status line, S00~Smn is the scan line, k0~km'n' is the button, R0~R7 is the equivalent pull-up resistor when the output of the status line R00~R07 is high, about 50k ohms, Ri0 ~Ri7 is the equivalent resistance value when the state lines R00~R07 are in the input high-impedance state, not less than 10M ohms. Originally, when scanning a button, set the status lines R00-R07 to output high, sequentially set the output of the scanning lines S00-Smn to low, and keep the output of the other scanning lines high, and read the status of the status lines R00-R07.
[0062] like figure 1 The middle line is a silver film material with a small resistance value. When scanning such as the scanning line S00, the scanning line S00 outputs a low level, and the other scanning lines are configured to ou...
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The invention provides a carbon film routing-based key scanning hardware circuit key scanning method. The method comprises a step of reading states of state lines. More particularly, when initialization is carried out, the state lines are configured to be in high output states; time delay is carried out; before the state lines are read, the state lines are configured to be in input modes and an equivalent pull-up resistor with an M level is used to obtain weak driving; a first stat line is individually configured to be in a high output state; time delay is carried out; the first state line is individually set into an input mode and the equivalent pull-up resistor is at the M level; time delay is carried out; the state of the first state line is read; a second state line is individually configured to be in a high output state; time delay is carried out; the second state line is individually set into an input mode and the equivalent pull-up resistor is at the M level; time delay is carried out; the state of the second state line is read; and then state of the rest of state lines are read successively in this way. According to the invention, a mode in which voltage supply is firstly carried out and then scanning is carried out is employed; and on the condition that no higher requirement on the hardware circuit structure is made, the influence on the scanning result by the routing capacitor is eliminated.
Description
technical field [0001] The present invention relates to the technical field of key scanning circuits. Specifically, the present invention relates to a key scanning method based on a carbon film wiring key scanning hardware circuit. Background technique [0002] In the existing key scanning circuit, the carbon film wiring is cheaper than the silver film wiring, but the resistance value is larger (10k-500k). And just because of its large resistance value, a large trace capacitance (5-7pF) is formed between the carbon film traces, so that the state interference between the traces is relatively large. Therefore, the original button scanning method is not applicable to the carbon film wiring button scanning circuit. Contents of the invention [0003] The technical problem to be solved by the present invention is to provide a key scanning method based on the key scanning hardware circuit of the carbon film wiring, which can overcome the influence of the wiring capacitance on th...
Claims
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IPC IPC(8): H03M11/20
Inventor 赵雄鹰林蔚
Owner SINO WEALTH ELECTRONICS