Keyboard key discrimination employing drive line/sense line combinations and accomodating simultaneous key press conditions
First Claim
1. A keyboard switch matrix for use in keyboard key discrimination, comprising:
- a plurality of drive lines;
a plurality of sense lines; and
a plurality of switches for selectively causing contact between the drive lines and sense lines upon actuation of associated keyboard keys, wherein;
a first set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, a first drive line with a first sense line and a second drive line with a second sense line whereby upon sequentially driving signals on said plurality of drive lines in a cyclical manner and sensing said signals that appear on said plurality of sense lines, an actuated key can be discriminated based upon said signals.
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Accused Products
Abstract
In a conventional 8×17 drive line/sense line keyboard switch matrix, a one-to-one correspondence between keyboard key switches and drive line/sense line pairs, together with a sequential driving of the drive lines, permits discrimination between 8×17=136 keyboard keys with 25 I/O pins. In contrast, the present invention utilizes drive line/sense line combinations to discriminate between keyboard keys with fewer total drive and sense lines, thereby reducing the number of required IC pin connections. In addition to achieving a reduction in the number of required pin connections, particular drive line/sense line contact patterns (e.g., a 2/2 pattern), and an associated subtraction algorithm, allow for efficient layouts of the drive lines and sense lines on respective membrane switch layers, a reduction of detection errors arising from inadvertent illegal simultaneous key presses, and discrimination of “special” simultaneous key press conditions.
45 Citations
15 Claims
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1. A keyboard switch matrix for use in keyboard key discrimination, comprising:
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a plurality of drive lines;
a plurality of sense lines; and
a plurality of switches for selectively causing contact between the drive lines and sense lines upon actuation of associated keyboard keys, wherein;
a first set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, a first drive line with a first sense line and a second drive line with a second sense line whereby upon sequentially driving signals on said plurality of drive lines in a cyclical manner and sensing said signals that appear on said plurality of sense lines, an actuated key can be discriminated based upon said signals. - View Dependent Claims (2, 3, 4, 5, 6)
said first drive line with said second sense line and said second drive line with a third sense line; and
said first sense line with said second drive line and said second sense line with a third drive line.
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3. The keyboard switch matrix of claim 2, wherein a third set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, one of:
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said first drive line with said third sense line and said second drive line with a fourth sense line; and
said first sense line with said third drive line and said second sense line with a fourth drive line.
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4. The keyboard switch matrix of claim 3, wherein a fourth set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, one of:
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said first drive line with said fourth sense line and said second drive line with a fifth sense line; and
said first sense line with said fourth drive line and said second sense line with a fifth drive line.
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5. The keyboard switch matrix of claim 4, wherein a fifth set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, one of:
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said first drive line with said fifth sense line and said second drive line with a sixth sense line; and
said first sense line with said fifth drive line and said second sense line with a sixth drive line.
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6. The keyboard switch matrix of claim 1, wherein a second set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, a single drive line with a single sense line.
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7. A keyboard switch circuit for providing key discrimination among a plurality of keyboard keys, the switch circuit comprising:
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a switch matrix comprising a plurality of drive lines, a plurality of sense lines and a plurality of switches for selectively causing contact between the drive lines and sense lines upon actuation of associated keyboard keys, wherein a first set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, a first drive line with a first sense line and a second drive line with a second sense line; and
an integrated circuit (IC) coupled to the plurality of drive lines and sense lines, the IC comprising logic circuitry for;
sequentially driving signals on said plurality of drive lines in a cyclical manner, and sensing said signals that appear on said plurality of sense lines; and
discriminating an actuated key based upon said signals. - View Dependent Claims (8, 9, 10, 11, 12, 13)
said first drive line with said second sense line and said second drive line with a third sense line; and
said first sense line with said second drive line and said second sense line with a third drive line.
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9. The keyboard switch circuit of claim 8, wherein a third set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, one of:
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said first drive line with said third sense line and said second drive line with a fourth sense line; and
said first sense line with said third drive line and said second sense line with a fourth drive line.
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10. The keyboard switch circuit of claim 9, wherein a fourth set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, one of:
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said first drive line with said fourth sense line and said second drive line with a fifth sense line; and
said first sense line with said fourth drive line and said second sense line with a fifth drive line.
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11. The keyboard switch circuit of claim 10, wherein a fifth set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, one of:
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said first drive line with said fifth sense line and said second drive line with a sixth sense line; and
said first sense line with said fifth drive line and said second sense line with a sixth drive line.
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12. A keyboard switch circuit according to claim 7, wherein a second set of said plurality of switches is arranged to bring into exclusive contact, upon actuation of an associated key, a single drive line with a single sense line.
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13. A keyboard switch circuit according to claim 7, wherein said logic circuitry implements a subtraction algorithm serving to read a new status of the keyboard and compare it to an old status to detect any new key presses or releases.
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14. A method for keyboard key discrimination, comprising:
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sequentially driving signals on a plurality of drive lines of a switch matrix in a cyclical manner;
sensing said signals that appear on a plurality of sense lines of said switch matrix as a result of a first drive line coming into exclusive contact with a first sense line and a second drive line coming into exclusive contact with a second sense line; and
discriminating an actuated key based upon said signals. - View Dependent Claims (15)
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Specification