Keyboard with reduced keying ambiguity
View Patent ↗When an array of proximity sensors is used as a keyboard, it can provide an ambiguous output if a user's finger overlaps several keys or if liquid is spilled on the keyboard. This ambiguity is reduced by an iterative method that repeatedly measures a detected signal strength associated with each key, compares all the measured signal strengths to find a maximum, determines that the key having the maximum signal strength is the unique user-selected key and then suppresses or ignores signals from all other keys as long as the signal from the selected key remains above some nominal threshold value.
1. An iterative method for controlling an array of non-bistable keys to uniquely determine which one, if any, key of the array thereof has been is being touched by a user, wherein each of the keys provides a respective signal output representative of the a respective coupling of the user thereto, the method comprising the iterated steps of:
comparing the respective signals from all the keys and;
only if a previous iteration determined that the one of the keys had been touched by the user, comparing die respective signal from the previously touched one of the keys with a selected signal threshold value; and if the signal from the previously touched one of the keys exceeds the selected signal threshold value, confirming the previously touched one of the keys to be the key being touched and decrementing a respective counter value uniquely associated with each of the other keys and otherwise;
selecting the key having the highest signal output associated therewith and, if the highest signal output exceeds a the selected signal threshold value, incrementing the respective associated counter value, comparing the incremented counter value with a selected terminal count value and, if the incremented counter value exceeds the terminal count value, determining that the key having the highest signal associated therewith is the touched key being touched and decrementing the respective counter value uniquely associated with each of the other keys; and
otherwise determining that no key has been is being touched by the user.
2. The method of claim 1 wherein a respective counter value is decremented by reducing it by one count subject to a condition that the value can not be reduced below zero.
3. The method of claim 1 wherein a respective counter value is decremented by setting it equal to zero.
4. The method of claim 1 wherein a respective counter value is decremented by setting it equal to a selected non-zero value.
5. The method of claim 1 wherein each key comprises a respective capacitive proximity sensor.
6. A keyboard for supplying a unique key output when a user is proximate two or more keys of a plurality thereof, the keyboard comprising:
a respective sensor uniquely associated with each of the two or more keys, each of the sensors connected to supply a respective output signal representative of the user's coupling thereto to both a controller and to a respective counter;
each counter arranged to count towards a terminal count when the respective proximity signal exceeds a selected signal threshold value and to supply the respective count value to the controller;
the controller for comparing arranged to compare all of the two or more output signals supplied thereto and to select as the key for supplying the unique key output that one of the two or more keys having a maximum of the count values used for supplying the unique key output.
7. The apparatus of claim 6 wherein the controller has an output to each of the counters for initializing a selected one of the counters.
8. The apparatus of claim 6 wherein a computer comprises the controller and all of the counters, the computer storing the signal threshold value and the terminal count value in memory.
9. The apparatus of claim 6 wherein each key comprises a respective capacitive proximity sensor.
10. In a keyboard comprising a plurality of touch responsive keys, wherein each of the keys has a respective signal output responsive to an extent of coupling to a user who touches the keyboard, an iterative method of determining a unique output, subsequent to the touch, the method comprising the steps of:
comparing the respective signal outputs from all the keys with each other and with a selected signal threshold value; and
if a previously selected key has a respective signal output in excess of the signal threshold value, confirming the previous selection of the one of the keys to supply the unique output while suppressing signals from all other keys;
if no key was selected in a previous iteration and at least one of the keys has a respective signal output in excess of the signal threshold value, selecting that one of the at least one of the keys baying the highest signal output value to supply the unique output; and
if no key has a respective signal output in excess of the signal threshold value, supplying a null output indicating that the user is no longer touching any of the keys.
11. The method of claim 10 wherein each of the keys comprises a respective capacitive proximity sensor.