Key input apparatus interface
First Claim
1. An interface for a key input apparatus to an electronic device, comprising:
- a resistive element having a ground point for connection to a ground potential, and three or more contact points such that the resistive element includes a plurality of pairs of first and second contact points in which the first and second contact points are adjacent to each other;
a plurality of key switches connected to an input point which is, in turn, connected to a voltage source, wherein each of the plurality of key switches is disposed with respect to a corresponding one of the plurality of contact points such that when one of the plurality of key switches is asserted to contact the corresponding contact point, an electrical path is formed from the input point to the ground point through the asserted key switch and at least a portion of the resistive element;
a sampling point on the electrical path for providing a sampling voltage to a decoder of the electronic device when one of the plurality of key switches is asserted; and
means for producing substantially equal sampling voltage differences for each of the plurality of pairs of first and second adjacent contact points, wherein a sampling voltage difference for a pair of first and second contact points is a difference between the magnitude of a first sampling voltage produced when the first contact point of the pair is contacted by a corresponding first key switch and the magnitude of a second sampling voltage produced when the second contact point of the pair is contacted by a corresponding second key switch.
5 Assignments
0 Petitions
Accused Products
Abstract
A compact key input apparatus interface includes a resistive element and a number of key contacts on the resistive element. The keys of a key input apparatus are disposed to provide electrical contact between a voltage source and the resistive element at a particular contact point when a corresponding key is depressed, such that a path from the voltage source to ground is made through the resistive element. The keys are arranged along the length of the resistive element so that the depression of any key provides a different conductive path to ground and therefore a different magnitude of current through the conductive path. A corresponding sense voltage measured at a sampling point provides a single-line input to a key decoder, which determines which key is depressed based on the level of the sense voltage.
28 Citations
24 Claims
-
1. An interface for a key input apparatus to an electronic device, comprising:
-
a resistive element having a ground point for connection to a ground potential, and three or more contact points such that the resistive element includes a plurality of pairs of first and second contact points in which the first and second contact points are adjacent to each other;
a plurality of key switches connected to an input point which is, in turn, connected to a voltage source, wherein each of the plurality of key switches is disposed with respect to a corresponding one of the plurality of contact points such that when one of the plurality of key switches is asserted to contact the corresponding contact point, an electrical path is formed from the input point to the ground point through the asserted key switch and at least a portion of the resistive element;
a sampling point on the electrical path for providing a sampling voltage to a decoder of the electronic device when one of the plurality of key switches is asserted; and
means for producing substantially equal sampling voltage differences for each of the plurality of pairs of first and second adjacent contact points, wherein a sampling voltage difference for a pair of first and second contact points is a difference between the magnitude of a first sampling voltage produced when the first contact point of the pair is contacted by a corresponding first key switch and the magnitude of a second sampling voltage produced when the second contact point of the pair is contacted by a corresponding second key switch. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. An interface for a key input apparatus to an electronic device, comprising:
-
a resistive element having a plurality of contact points and a ground point for connection to a ground potential, wherein the resistive element has a first portion over which all of the plurality of contact points are spaced and a second portion, adjacent to the first portion, having a resistance that is at least as great as a resistance of the first portion;
a plurality of key switches connected to an input point which is, in turn, connected to a voltage source, wherein each of the plurality of key switches is disposed with respect to a corresponding one of the plurality of contact points such that when one of the plurality of key switches is asserted, electrical connection is made between the corresponding contact point and the input point, forming an electrical path from the input point to the ground point through the asserted key switch and at least a portion of the resistive element; and
a sampling point on the electrical path for providing a sampling voltage to a decoder of the electronic device when one of the plurality of key switches is asserted. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
-
-
24. An interface for a key input apparatus to an electronic device, comprising:
-
a resistive element having a plurality of contact points and a ground point for connection to a ground potential, wherein the resistive element is integrally formed with a printed circuit board;
a plurality of key switches connected to an input point which is, in turn, connected to a voltage source, wherein each of the plurality of key switches is disposed with respect to a corresponding one of the plurality of contact points such that when one of the plurality of key switches is asserted, electrical connection is made between the corresponding contact point and the input point, forming an electrical path from the input point to the ground point through the asserted key switch and at least a portion of the resistive element; and
a sampling point on the electrical path for providing a sampling voltage to a decoder of the electronic device when one of the plurality of key switches is asserted.
-
Specification