Keypad
OwnerAndrew R Jamieson, David J McGregorinventors
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Abstract
A keypad is disclosed which has a plurality of keys (12) for the input of information. Each key has a first switch (80) and a second switch (90). The first switches (80) are all connected to a common electrical interconnection (120) and the second switches (90) are connected into a matrix electrical interconnection (62, 100). The microprocessor (66) detects a global signal on the common interconnection (120) and supplies scan signals to the matrix interconnection (62, 100) to enable detection of a particular key. The processor (66) may also selectively change the state of lines (62, 100) of the matrix and also maintain particular lines in a predetermined state by open drain ports of the processor to which the lines of the matrix are connected.
Claims22
A keypad comprising:
- a plurality of keys, wherein each key in the plurality of keys is coupled to a first switch, the first switch being coupled to a common electrical interconnection, and a second switch, the second switch being coupled to a matrix electrical interconnection, wherein the matrix electrical interconnection includes one or more row lines and one or more column lines;
- and
- a controller configured to detect a signal on the common electrical interconnection and configured to provide a scan signal to the matrix electrical interconnection,
- wherein, responsive to detecting a change of state in the signal on the common electrical interconnection indicating that a first key in the plurality of keys has been depressed, the controller is further configured to:
- direct the scan signal to a corresponding column line in the one or more column lines,
- direct dummy signals to at least one row line, and
- read the one or more row lines associated with the corresponding column line to detect the first key in the plurality of keys.
A method comprising:
- detecting a change of state in a signal on a common electrical interconnection in response to a key in a plurality of keys being depressed;
- directing a scan signal to a corresponding column line in one or more column lines and dummy signals being substantially equivalent to the scan signal to at least one row line of one or more row lines based on detecting a change of state in the signal on the common electrical interconnection, wherein the dummy signals are directed after the detection of the change of state in the signal on the common electrical interconnection;
- and
- reading the one or more row lines to detect the depressed key.
Dependencies are inferred from the claim text.