Apparatus and method for preventing false touches in touch screen systems

1. A method comprising:

in a frame period, scanning a touch screen panel from a first corner to a second corner, wherein the touch screen panel comprises a plurality of sensors arranged in rows and columns and the first corner is diagonally opposite to the second corner;

determining whether a sensor is affected by electrical fast transient (EFT) noise;

considering a frame as a noise influenced frame if a total number of sensors affected by EFT noise is greater than a first noise threshold;

discarding the noise influenced frame without further processing;

finding a first noise influenced sensor;

determining whether the first noise influenced sensor is located at a last transmitting/driving line of the touch screen panel;

determining whether a frame is a noise influenced frame by a second noise threshold;

finding all noise influenced sensors in the last transmitting/driving line of the touch screen panel;

calculating a percentage equal to the number of noise influenced sensors divided by the number of samples between the first noise influenced sensor and a last sensor of the last transmitting/driving line of the touch screen panel; and

considering the frame as a noise influenced frame if the percentage is greater than 60%.

2. The method of claim 1 , wherein:

the first corner is an upper left corner; and

the second corner is a bottom right corner.

3. The method of claim 1 , wherein determining whether a sensor is affected by EFT noise further comprises:

setting a first threshold and a first hysteresis band, wherein the first threshold is less than a baseline of the touch screen panel;

comparing a signal generated by the sensor with the first threshold; and

labeling the sensor as a noise influenced sensor if signal strength of the signal exceeds the first threshold.

4. The method of claim 3 , wherein:

the baseline is about 1000;

the first threshold is about 900; and

the first hysteresis band is from 900 to 950.

5. The method of claim 1 , wherein:

the first noise threshold is 40.

6. A method comprising:

during a frame period, finding a first EFT noise influenced sensor of a touch screen panel;

determining whether the first EFT noise influenced sensor is located at a last transmitting/driving line of the touch screen panel;

designating the frame period as a noise influenced frame period using an absolute value threshold if the first EFT noise influenced sensor is not located at the last transmitting/driving line; and

designating the frame period as the noise influenced frame period using a percentage threshold if the first EFT noise influenced sensor is located at the last transmitting/driving line, wherein designating the frame period as the noise influenced frame period using a percentage threshold comprises:

finding a first EFT triggered touch point in a last transmitting/driving line of a touch frame;

calculating a percentage of EFT triggered touch points over a sample from the first EFT triggered touch point to a last touch point of the last transmitting/driving line of the touch frame; and

discarding the touch frame if the percentage of EFT triggered touch points is greater than the percentage threshold.

7. The method of claim 6 , further comprising:

receiving raw signals from the touch screen panel; and

finding a first EFT noise influenced signal based upon a first predetermined threshold.

8. The method of claim 7 , wherein:

the first predetermined threshold is a capacitance variation from a baseline of the touch screen panel.

9. The method of claim 8 , wherein:

the first predetermined threshold is 900 when a baseline of the touch screen panel is 1000.

10. The method of claim 9 , further comprising:

a hysteresis band around the first predetermined threshold.

11. The method of claim 6 , further comprising:

finding a first EFT triggered touch point from a touch frame;

counting a total number of EFT triggered touch points; and

dropping the touch frame if the total number of EFT triggered touch points is greater than the absolute value threshold.

12. The method of claim 6 , wherein:

the percentage threshold is about 60%.

13. The method of claim 6 , wherein designating the frame period as the noise influenced frame period using the percentage threshold further comprises designating the frame period as the noise influenced frame period when 60% or more of a sampled group of sensors are noised influenced.

14. The method of claim 6 , wherein the percentage threshold is 60%.

15. A system comprising:

a touch screen panel comprising a plurality of sensors arranged in rows and columns, wherein each sensor comprises:

a transmit node; and

a receive node, wherein the transmit node and the receive node form a capacitor;

a receiver coupled to the receive node; and

a processor coupled to the receiver, wherein the processor is configured to:

find a first EFT noise influenced sensor of the touch screen panel;

determine whether the first EFT noise influenced sensor is located at a last transmitting/driving line of the touch screen panel;

designate a touch frame as a noise influenced frame using an absolute value threshold if the first EFT noise influenced sensor is not located at the last transmitting/driving line;

designate the touch frame as the noise influenced frame using a percentage threshold if the first EFT noise influenced sensor is located at the last transmitting/driving line; and

calculate a percentage equal to the number of noise influenced sensors divided by the number of samples between a first sensor and a last sensor of the last transmitting/driving line of the touch screen panel and wherein the touch frame is designated as a noise influenced frame when the percentage is greater than 60%.

16. A system comprising:

a touch screen panel comprising a plurality of sensors arranged in rows and columns, wherein each sensor comprises:

a transmit node; and

a receive node, wherein the transmit node and the receive node form a capacitor;

a receiver coupled to the receive node; and

a processor coupled to the receiver, wherein the processor is configured to:

find a first EFT noise influenced sensor of the touch screen panel;

determine whether the first EFT noise influenced sensor is located at a last transmitting/driving line of the touch screen panel;

designate a touch frame as a noise influenced frame using an absolute value threshold if the first EFT noise influenced sensor is not located at the last transmitting/driving line; and

designate the touch frame as the noise influenced frame using a percentage threshold if the first EFT noise influenced sensor is located at the last transmitting/driving line, wherein designating the touch frame as the noise influenced frame using a percentage threshold comprises:

calculating a percentage of EFT noise influenced sensors over a sample from the first EFT noise influenced sensor to a last EFT noise influenced sensor of the last transmitting/driving line of the touch screen panel for the touch frame;

comparing the percentage of EFT noise influenced sensors with the percentage threshold; and

discarding the touch frame if the percentage of EFT noise influenced sensors is greater than the percentage threshold.

17. The system of claim 16 , wherein:

the processor receives raw data from the touch screen panel through the receiver.

18. The system of claim 16 , wherein:

the touch frame is of 12 rows and 20 columns.

19. The system of claim 16 , wherein:

the absolute value threshold is about 40; and

the percentage threshold is about 60%.

20. The system of claim 16 , wherein:

the processor finds the first EFT noise influenced sensor by measuring signal strength of a signal generated by the first EFT noise influenced sensor.