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. A method of removing keying ambiguity in a keyboard comprising an array of keys, the method comprising repeating the following steps;(a) receiving from each of the keys a respective signal indicative of a degree of coupling between each key and a potential user;(b) comparing the measured signals to determine the key having a maximum signal strength associated therewith;(c) designating the key having the maximum signal strength as the user-selected key; and(d) maintaining the key having the maximum signal strength as the user-selected key until the signal from that key falls below a threshold value, wherein signals from all other keys are suppressed or ignored during the maintaining step.
2. The method of claim 1 wherein each key comprises a capacitive sensor.
3. The method of claim 1 further comprising a step of decrementing a respective counter value uniquely associated with each of the other keys if the key is maintained as the user-selected key; otherwise selecting the key having the maximum signal strength associated therewith and, if the maximum signal strength exceeds a selected signal threshold value, incrementing a respective associated counter value, comparing the incremented counter value with a selected terminal count value and, if the incremented counter value is equal to the terminal count value, determining that the key having the maximum signal strength associated therewith is the user-selected key and decrementing the respective counter value uniquely associated with each of the other keys; and otherwise determining that no key has been touched by the user.
4. The method of claim 3 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.
5. The method of claim 3 wherein a respective counter value is decremented by setting it equal to zero.
6. The method of claim 3 wherein each key comprises a respective capacitive sensor.
7. The method of claim 1 further comprising a step of incrementing a respective counter value uniquely associated with each of the other keys if the key is maintained as the user-selected key; otherwise selecting the key having the maximum signal strength associated therewith and, if the maximum signal strength exceeds a selected signal threshold value, decrementing the respective associated counter value, comparing the decremented counter value with a selected terminal count value and, if the decremented counter value is equal to the terminal count value, determining that the key having the maximum signal strength associated therewith is the user-selected key and incrementing the respective counter value uniquely associated with each of the other keys; and otherwise determining that no key has been touched by the user.
8. The method of claim 7 wherein a respective counter value is incremented by increasing it by one count subject to a condition that the value can not exceed the terminal count.
9. The method of claim 7 wherein a respective counter value is incremented by setting it equal to the terminal count.
10. An apparatus comprising: a keyboard comprising a plurality of keys, each key comprising a respective sensor having a respective output connection for supplying a respective proximity signal representative of a user's coupling to that key; and a controller connected to receive the proximity signals from the keys, the controller having an output for transmitting a selected key output signal, wherein the controller comprises logic for resolving keying ambiguities which, in the event of the controller simultaneously receiving more than one proximity signal, the controller selects the key having the largest proximity signal and maintains that key as the selected key until the proximity signal from that key falls below a threshold value, characterized in that the controller is operable to suppress or ignore signals from all other keys while the selected key is maintained.
11. The apparatus of claim 10 further comprising a plurality of filters, each filter associated with a respective key, wherein each filter is operable to block transit of the respective proximity signal to the controller until the respective proximity signal has exceeded a threshold value for at least a selected period of time.
12. The apparatus of claim 11 wherein the filters are counters and wherein the selected period of time relates to an integral number of count cycles, each counter being configured to increment or decrement after each cycle during which the respective proximity signal continues to exceed the threshold value.
13. The apparatus of claim 10 further comprising a plurality of counters, each counter associated with a respective key, wherein each counter is operable to block transit of the respective proximity signal to the controller until the respective proximity signal has exceeded a threshold value for at least a selected integral number of count cycles.
14. The apparatus of claim 10 wherein the sensors are capacitive sensors.
15. The apparatus of claim 10 wherein the controller is housed in a separate unit from the keyboard.
16. The apparatus of claim 10 wherein the controller is housed in the same unit as the keyboard.
17. The apparatus of claim 10 , further comprising a respective counter associated with each key and arranged to change a counter value when the respective proximity signal exceeds the selected signal threshold value, each counter for supplying the respective associated signal value to the controller when a respective count is equal to a selected terminal count value; the controller for comparing all of the two or more output signals supplied thereto to select that one of the two or more keys used for supplying the unique key output.
18. The apparatus of claim 17 wherein the controller has an output to each of the counters for resetting a selected one of the counters.
19. The apparatus of claim 17 further comprising a computer, wherein the computer hosts the controller and all of the counters, the computer storing the signal threshold value and the terminal count value in memory.
20. The apparatus of claim 17 wherein each key comprises a respective capacitive sensor.