System and method for verifying entry of keystrokes received from a capacitive keypad

1. A method of data entry for an appliance comprising:

receiving a key code from a key decoder that corresponds to a first capacitive key of a capacitive keypad;

detecting a ghosting condition for a second capacitive key that does not correspond to the received key code; and

resetting a key decoder in response to the ghosting condition being detected.

2. The method of claim 1 further comprising:

activating a ghosting condition timer in response to the detection of the ghosting condition;

monitoring the second capacitive key for the detected ghosting condition as the ghosting condition timer is counting; and

resetting the key decoder in response to the ghosting condition existing for the second capacitive key upon expiration of the ghosting condition timer.

3. The method of claim 1 , the ghosting condition detection further comprising:

coupling a signal from the second capacitive key to a ghost condition comparator; and

comparing the coupled signal to a ghosting threshold to detect the ghosting condition.

4. The method of claim 3 , the ghosting condition detection further comprising:

receiving an invalid key code for the first capacitive key; and

terminating ghosting condition detection in response to the invalid key code being received.

5. The method of claim 4 , the ghosting condition detection further comprising:

receiving a key code that identifies the first capacitive key as a safety-related key; and

terminating ghosting condition detection in response to the safety-related key code being received.

6. The method of claim 1 , the monitoring of the ghosting condition comprising:

coupling a signal from at least three capacitive keys in the plurality of capacitive keys, none of the at least three capacitive keys corresponding to the first capacitive key;

comparing the signal from each of the at least three capacitive keys to a ghosting threshold to detect the ghosting condition; and

terminating detection of the ghosting condition in response to each of the signals from the at least three capacitive keys being equal to or greater than the ghosting threshold.

7. The method of claim 1 , the monitoring of the ghosting condition comprising:

coupling a signal from each capacitive key in the plurality of capacitive keys not corresponding to the first capacitive key;

comparing the signal from each capacitive key in the plurality of capacitive keys to a ghosting threshold to detect the ghosting condition; and

terminating detection of the ghosting condition in response to every signal from each capacitive key in the plurality of capacitive keys being equal to or greater than the ghosting threshold.

8. A data entry system for use in an appliance, comprising:

a key decoder coupled to a plurality of capacitive keys, the key decoder generates a code corresponding to a capacitive key transitioning to a capacitance indicative of a key being touched;

a key selector coupled to the key decoder, the key selector for selecting a signal from at least one key in the plurality of capacitive keys that does not correspond to the key code received from the key decoder;

a ghost condition detector being coupled to the signal selected by the key selector and being configured to detect a ghosting condition with reference to a ghosting threshold coupled to the ghost condition detector.

9. The data entry system of claim 8 , the ghost condition detector further comprising:

a ghost condition comparator having an input coupled to the signal selected by the key selector and another input coupled to the ghosting threshold, the ghost condition comparator generating a ghost condition active signal in response to the selected signal being equal to or greater than the ghosting threshold; and

the key decoder being coupled to the ghost condition comparator so the key decoder is reset in response to the ghost condition active signal being generated by the ghost condition comparator.

10. The data entry system of claim 8 further comprising:

a ghost condition timer coupled to the ghost condition comparator, the ghost condition timer being activated in response to the ghost condition comparator generating a ghost condition active signal; and

the key decoder being reset in response to the ghost condition timer expiring and the ghost condition active signal continuing to be generated by the ghost condition comparator at expiration of the ghost condition timer.

11. The data entry system of claim 10 , the key selector not selecting a signal from a capacitive key in response to the key decoder generating a safety-related key code.

12. The data entry system of claim 11 , the key selector not selecting a signal from a capacitive key in response to the key decoder generating an invalid key code.

13. The data entry system of claim 8 , the key selector selecting signals from more than one key in the plurality of capacitive keys, each selected signal corresponding to a key other than the key corresponding to the key code generated by the key decoder; and

each selected signal being coupled to the ghost condition detector and the ghost condition detector being further configured to detect a ghosting condition with reference to each selected signal and the ghosting threshold.

14. The data entry system of claim 13 , the ghost condition detector further comprising:

a plurality of ghost condition comparators, each comparator having an input coupled to one of the selected signals and another input coupled to the ghosting threshold, each ghost condition comparator generating a ghost condition active signal in response to the selected signal on the comparator's input being equal to or greater than the ghosting threshold.

15. The data entry system of claim 14 , the outputs of the ghost condition comparators being coupled to a logical OR circuit and a ghost condition active signal is generated by the OR circuit in response to one of the selected signals being equal to or greater than the ghosting threshold.

16. The data entry system of claim 14 , the outputs of the ghost condition comparators being coupled to a logical AND circuit and a ghost condition active signal is generated by the AND circuit in response to all of the selected signals being equal to or greater than the ghosting threshold.

17. The data entry system of claim 14 , the outputs of the ghost condition comparators being coupled to a majority circuit and a ghost condition active signal is generated by the majority circuit in response to one half or more of the selected signals being equal to or greater than the ghosting threshold.

18. The data entry system of claim 14 further comprising:

a ghost condition timer coupled to each ghost condition comparator, the ghost condition timer being activated in response to one ghost condition comparator generating a ghost condition active signal; and

the key decoder being reset in response to the ghost condition timer expiring and the ghost condition active signal continuing to be generated by the ghost condition comparator at expiration of the ghost condition timer.

19. The data entry system of claim 16 further comprising:

a ghost condition timer coupled to the AND circuit, the ghost condition timer being activated in response to the ghost condition active signal being generated by the AND circuit; and

the key decoder being reset in response to the ghost condition timer expiring and the ghost condition active signal continuing to be generated by the AND circuit at expiration of the ghost condition timer.

20. The data entry system of claim 17 further comprising:

a ghost condition timer coupled to the majority circuit, the ghost condition timer being activated in response to the ghost condition active signal being generated by the majority circuit; and

the key decoder being reset in response to the ghost condition timer expiring and the ghost condition active signal continuing to be generated by the majority circuit at expiration of the ghost condition timer.