Touch screen driver for resolving plural contemporaneous touches and methods for use therewith

• US 8,106,892 B2
• Filed: 10/29/2007
• Issued: 01/31/2012
• Est. Priority Date: 10/29/2007
• Status: Expired due to Fees

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: SigmaTel Incorporated (NXP Semiconductors NV)
• Inventors: Felder, Matthew D., May, Marcus W.
• Primary Examiner(s): Lefkowitz, Sumati
• Assistant Examiner(s): Carter, III, Robert E
• Application Number:
  US11/927,289
• Publication Number:
  US 20090109191A1
• Time in Patent Office: 1,555 Days
• Field of Search: 345173-174, 178/18.05
• US Class Current: 345/174
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

A touch screen driver that can be used with a resistive touch screen includes an input/output module that supplies at least one input signal to at least one of a plurality of input/output ports of the touch screen and that generates at least one output signal, in response to the at least one input signal, and in accordance with at least one control signal. A controller module generates the at least one control signal and that generates a position signal representing a resolved position in accordance with a plurality of contemporaneous touches of the resistive touch screen.

Claims

1. A touch screen driver for use with a resistive touch screen, the touch screen driver comprising:

an input/output module, coupled to the resistive touch screen, that supplies at least one input signal to at least one of a plurality of input/output ports of the resistive touch screen and that generates at least one output signal, in response to the at least one input signal, and in accordance with at least one control signal;

a controller module, coupled to the input/output module, that generates the at least one control signal and that generates a position signal representing a resolved position in accordance with a plurality of contemporaneous touches of the resistive touch screen; and

wherein the resolved position includes a position of a first touch of the plurality of contemporaneous touches and a position of a second touch of the plurality of contemporaneous touches, and wherein the controller module generates the resolved position by;

generating a center between the first touch and the second touch;

generating a distance between the first touch and the second touch;

generating the position of the first touch based on the center and the distance and further based on a disambiguation procedure; and

determining the position of the second touch based on the center and the distance and further based on the disambiguation procedure.

2. The touch screen driver of claim 1 wherein the position signal includes an X-position and a Y-position, the plurality of input/output ports includes a plurality of X panel ports and a plurality of Y panel ports, the at least one control signal includes a first control signal and a second control signal, the at least one output signal includes a first plurality of output signals and a second plurality of output signals, and wherein the controller module generates the position signal by:

generating the first control signal that commands the input/output module to drive at least one of the plurality of X panel ports and to generate the first plurality of output signals from the plurality of Y panel ports;

generating the second control signal that commands the input/output module to drive at least one of the plurality of Y panel ports and to generate the second plurality of output signals from the plurality of X panel ports;

generating the X-position based on an average of the first plurality of output signals; and

generating the Y-position based on an average of the second plurality of output signals.

3. The touch screen driver of claim 1 wherein the position signal includes an X-distance and a Y-distance, the plurality of input/output ports includes a plurality of X panel ports and a plurality of Y panel ports, the at least one control signal includes a first control signal and a second control signal, the at least one output signal includes a first output signal and a second output signal, and wherein the controller module generates the position signal by:

generating the first control signal that commands the input/output module to drive at least one of the plurality of X panel ports and to generate the first output signal from at least one of the plurality of X panel ports;

generating the second control signal that commands the input/output module to drive at least one of the plurality of Y panel ports and to generate the second output signal from at least one of the plurality of Y panel ports;

generating the X-distance based on the first output signal; and

generating the Y-distance based on the second output signal.

4. The touch screen driver of claim 3 wherein the first output signal corresponds to an impedance across the plurality of X panel ports, the second output signal corresponds to an impedance across the plurality of Y panel ports, wherein the control module generates the X-distance based on a function of the first output signal and the second output signal ,and wherein the control module generates the Y-distance based on a function of the first output signal and the second output signal.

5. The touch screen driver of claim 1 wherein the plurality of input/output ports includes a plurality of X panel ports and a plurality of Y panel ports, the at least one control signal includes a first control signal and a second control signal, the at least one output signal includes a first output signal and a second output signal, and wherein the disambiguation procedure performed by the controller module includes:

generating the first output signal based on an impedance between a first port of the plurality of X panel ports and a second port of the plurality of Y panel ports;

and further includes at least one of;

generating the second output signal based on an impedance between the first port of the plurality of X panel ports and a third port of the plurality of Y panel ports; and

generating the second output signal based on an impedance between the third port of the plurality of X panel ports and the second port of the plurality of Y panel ports.

6. The touch screen driver of claim 5 wherein the disambiguation procedure performed by the controller module further includes:

generating a first candidate and a second candidate for the position of the first touch;

comparing the first output signal to the second output signal;

choosing the first candidate for the position of the first touch when the first output signal compares unfavorably to the second output signal; and

choosing the second candidate for the position of the first touch when the first output signal compares favorably to the second output signal.

7. The touch screen driver of claim 1 wherein the plurality of input/output ports includes a X+ port a X−

port a Y+ port and a Y−

port, the at least one output signal includes a first output signal, a second output signal, a third output signal and a fourth output signal, and wherein the disambiguation procedure performed by the controller module includes;

generating a first output signal based on an impedance between the X+ port and the Y−

port;

generating a second output signal based on the an impedance between the X−

port and the Y+ port;

generating a third output signal based on an impedance between the X+ port and the Y+ port;

generating a fourth output signal based on the an impedance between the X−

port and the Y−

port;

generating a first sum based on a sum of the first output signal and the second output signal;

generating a second sum based on a sum of the third output signal and the fourth output signal;

generating a first candidate and a second candidate for the position of the first touch;

comparing the first sum to the second sum;

choosing the first candidate for the position of the first touch when the first sum compares unfavorably to the second sum; and

choosing the second candidate for the position of the first touch when the first sum compares favorably to the second sum.

8. A touch screen driver for use with a touch screen, the touch screen driver comprising:

an input/output module, coupled to the touch screen, that supplies a plurality of input signals to at least one of a plurality of input/output ports of the touch screen and generates a plurality of output signals, in response to the plurality of input signals, and in accordance with at least one control signal; and

a controller module, coupled to the input/output module, that generates the at least one control signal and that generates a first position signal representing a position of a first touch of the touch screen and a second position signal representing a second touch of the touch screen, wherein the first touch begins before the beginning of the second touch, wherein the first touch continues during at least a portion of the second touch, and wherein the controller module generates the first position signal based on a first output signal of the plurality of output signals generated before the beginning of the second touch, wherein the controller module generates the first position signal and the second signal based upon a center between the first touch and the second touch, a distance between the first touch and the second touch, and a disambiguation procedure.

9. A touch screen driver of claim 8 wherein the controller module generates the second position signal based on a second output signal of the plurality of output signals generated after the beginning of the second touch.

10. A method for use with a resistive touch screen, the method comprising:

generating at least one input signal to at least one of a plurality of input/output ports of the resistive touch screen;

generating at least one output signal, in response to the at least one input signal; and

generating a position signal representing a resolved position in accordance with a plurality of contemporaneous touches of the resistive touch screen, based on the at least one output signal, wherein generating the position signal includes;

generating a center between a first touch and a second touch;

generating a distance between the first touch and the second touch;

generating the position of the first touch based on the center and the distance and further based on a disambiguation procedure; and

determining the position of the second touch based on the center and the distance and further based on the disambiguation procedure.

11. The method of claim 10 wherein the position signal includes an X-position and a V-position, the plurality of input/output ports includes a plurality of X panel ports and a plurality of Y panel ports;

wherein generating the at least one input signal includes generating a first input signal to drive at least one of the plurality of X panel ports and generating at least one output signal includes generating a first plurality of output signals from the plurality of Y panel ports;

wherein generating the at least one input signal further includes generating a second input signal to drive at least one of the plurality of Y panel ports and generating at least one output signal further includes generating a second plurality of output signals from the plurality of X panel ports; and

wherein generating the position signal includes;

generating the X-position based on an average of the first plurality of output signals; and

generating the Y-position based on an average of the second plurality of output signals

12. The method of claim 10 wherein the position signal includes an X-distance and a Y-distance, the plurality of input/output ports includes a plurality of X panel ports and a plurality of Y panel ports;

wherein generating the at least one input signal includes generating a first input signal to drive at least one of the plurality of X panel ports and generating the at least one output signal includes generating a first output signal from at least one of the plurality of X panel ports;

wherein generating the at least one input signal further includes generating a second input signal to drive at least one of the plurality of Y panel ports and generating the at least one output signal includes generating a second output signal from at least one of the plurality of Y panel ports; and

wherein generating the position signal includes;

generating the X-distance based on the first output signal; and

generating the Y-distance based on the second output signal.

13. The method of claim 12 wherein the first output signal corresponds to an impedance across the plurality of X panel ports, the second output signal corresponds to an impedance across the plurality of Y panel ports, wherein generating the X-distance includes generating the X-distance based on a function of the first output signal and the second output signal, and wherein the control module generates the Y-distance based on a function of the first output signal and the second output signal.

14. The method of claim 10 wherein the plurality of input/output ports includes a plurality of X panel ports and a plurality of Y panel ports;

wherein generating the at least, one output signal includes generating a first output signal based on an impedance between a first port of the plurality of X panel ports and a second port of the plurality of Y panel ports;

wherein generating the at least one output signal further includes at least one of;

generating the second output signal based on an impedance between the first port of the plurality of X panel ports and a third port of the plurality of Y panel ports; and

generating the second output signal based on an impedance between a third port of the plurality of X panel ports and the second port of the plurality of Y panel ports.

15. The method of claim 14 wherein the disambiguation procedure includes:

generating a first candidate and a second candidate for the position of the first touch;

comparing the first output signal to the second output signal;

choosing the first candidate for the position of the first touch when the first output signal compares unfavorably to the second output signal; and

choosing the second candidate for the position of the first touch when the first output signal compares favorably to the second output signal.

16. The method of claim 10 wherein the plurality of input/output ports includes a X+ port a X−

port a Y+ port and a Y−

port, the at least one output signal includes a first output signal, a second output signal, a third output signal and a fourth output signal, and wherein the disambiguation procedure includes;

generating the first output signal based on an impedance between the X+ port and the Y−

port;

generating the second output signal based on the an impedance between the X−

port and the Y + port;

generating the third output signal based on an impedance between the X+ port and the Y+ port;

generating the fourth output signal based on the an impedance between the X−

port and the Y−

port;

generating a first sum based on a sum of the first output signal and the second 5 output signal;

generating a second sum based on a sum of the third output signal and the fourth output signal;

generating a first candidate and a second candidate for the position of the first touch;

comparing the first sum to the second sum;

choosing the first candidate for the position of the first touch when the first sum compares unfavorably to the second sum; and

choosing the second candidate for the position of the first touch when the first sum compares favorably to the second sum.