Key activity detection system and method thereof

1. A key activity detection method applied in an electronic device having at least a first key and a digital input/output (I/O) pin, comprising:

switching the digital I/O pin to a first operation mode, so that a voltage of the digital I/O pin is decreased to a ground voltage;

switching the digital I/O pin to a second operation mode, so that the voltage of the digital I/O pin is increased;

measuring a first charge period of the voltage of the digital I/O pin;

a first counting step of counting a first number of times the first charge period occurs; and

judging whether the first key is stably activated according to the first counted number.

2. The method according to claim 1 , wherein, during the first charge period, the voltage of the digital I/O pin is increased to a level exceeding a voltage threshold from the ground voltage.

3. The method according to claim 1 , wherein, the first counting step comprises:

accumulating the counted first number if a duration of the first charge period does not change; and

resetting the counted first number if the duration of the first charge period changes.

4. The method according to claim 1 , further comprising:

judging that the first key is stably activated if the counted first number is larger than or equal to a count threshold.

5. The method according to claim 1 , wherein, the electronic device further comprises a second key.

6. The method according to claim 5 , further comprising:

judging the first key or the second key is stably activated according to a duration of the first charge period if the counted first number is larger than or equal to a count threshold.

7. The method according to claim 5 , further comprising:

counting a difference between the first charge period and the second charge period if the first charge period is not equal to a second charge period, wherein, the counted first number of times and a counted second number of times the second charge period occurs are both larger than or equal to the count threshold;

judging the first key and/or the second key is stably activated according to the difference between the first charge period and the second charge period;

judging the first key and/or the second key is released if the first charge period is longer than the second charge period; and

judging the first key and/or the second key is pressed if the first charge period is shorter than the second charge period.

8. A key activity detection system, comprising:

at least a first key;

a first capacitor coupled to the first key;

a digital I/O pin coupled to the first key; and

a controller coupled to the digital I/O pin and the first key;

wherein during mode switching, a voltage of the digital I/O pin is increased/decreased, the controller measures a first charge period of the voltage of the digital I/O pin, and determines that the first key is stably activated if a first number of times the first charge period occurs exceeds a count threshold.

9. The key activity detection system according to claim 8 , wherein,

under the control of the controller, the digital I/O pin is switched to a first operation mode, so that the voltage of the digital I/O pin is decreased to a ground voltage;

under the control of the controller, the digital I/O pin is switched to a second operation mode;

the controller measures that the voltage of the digital I/O pin is increased to a level exceeding a voltage threshold from the ground voltage during the first charge period;

the controller counts the first number.

10. The key activity detection system according to claim 9 , wherein,

the controller accumulates the counted first number if a duration of the first charge period does not change; and

the controller resets the counted first number if the duration of the first charge period changes.

11. The key activity detection system according to claim 10 , wherein the electronic device further comprises a second key.

12. The key activity detection system according to claim 11 , wherein the controller judges the first key or the second key is stably activated according to a duration of the first charge period if the counted first number is larger than or equal to a count threshold.

13. The key activity detection system according to claim 11 , wherein,

if the first charge period is not equal to a second charge period, the controller calculates a difference between the first charge period and the second charge period wherein the first number, and a second appearance times of number of times the second charge period occurs are both larger than or equal to the count threshold;

the controller judges the first key and/or the second key is stably activated according to the difference between the first charge period and the second charge period;

the controller determines that the first key and/or the second key is released if the first charge period is longer than the second charge period; and

the controller determines that the first key and/or the second key is pressed if the first charge period is shorter than the second charge period.