Processing analog to digital converter signals to a touch screen display

• US 7,202,858 B2
• Filed: 02/17/2004
• Issued: 04/10/2007
• Est. Priority Date: 10/19/2001
• Status: Active Grant

• Current Assignee: Trane International Inc. (Trane Technologies plc)
• Original Assignee: American Standard Companies Incorporated (Ideal Standard International Topco SCA)
• Inventors: DeGroot, Jeffrey J., Krajewski, Thomas G.
• Primary Examiner(s): Shalwala; Bipin
• Assistant Examiner(s): Kovalick; Vincent E.
• Application Number:
  US10/779,926
• Publication Number:
  US 20040160426A1
• Time in Patent Office: 1,148 Days
• Field of Search: 345/90, 345/156, 345/173, 345/204, 178/18.01, 178/18.1, 341/5
• US Class Current: 345/173
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

An enhanced touch-screen display system is disclosed for generating pixel coordinate estimates corresponding to a location on a display screen touched by a user. The system is an analog resistive touch-screen display system having a processor and associated software algorithms to allow for the calibration and validation of pixel coordinate estimates as an integral part of the real-time generation of the pixel coordinate estimates. Multiple calibrated pixel coordinate estimates are generated and processed at a pre-defined sampling rate to determine a valid pixel position to minimize sampling delays due to settling times. The x-axis position is also validated before the system attempts to generate a y-axis position to avoid the wasted time for generating y-axis estimates when x-axis estimates are corrupted. Noisy estimates are inherently reduced in the touch-screen display system by providing shunts across certain drivers in the system that also allow for detection of a “no touch” state.

Claims

1. A method of speeding up the reading of analog to digital converter signals to a touch screen comprising the steps of:

reading a first coordinate of a coordinate pair at a first time;

consecutively reading the same coordinate at a second time;

determining if the absolute value of the difference between the first coordinate and the consecutive coordinate is less than a predetermined value; and

quantifying, responsive to the difference determining step the coordinate position as a function of the first or the consecutive coordinate.

2. The method of claim 1 wherein the consecutive coordinate is used as the coordinate position.

3. The method of claim 2 wherein the steps are repeated for the other desired coordinate position.

4. The method of claim 2 wherein the steps are repeated for the other desired coordinate position.

5. The method of claim 2 wherein the steps are repeated for the other desired coordinate position.

6. The method of claim 1 wherein the consecutive coordinate is used as the coordinate position.

7. The method of claim 1 wherein the consecutive coordinate is used as the coordinate position.

8. Apparatus speeding up the reading of analog to digital converter signals to a touch screen comprising:

means for reading a first coordinate of a coordinate pair at a first time;

means for consecutively reading the same coordinate at a second time;

means for determining if the absolute value of the difference between the first coordinate and the consecutive coordinate is less than a predetermined value; and

means, response to the determining means, for quantifying the coordinate position as a function of the first or the consecutive coordinate.

9. The apparatus of claim 8 wherein the consecutive coordinate is used as the coordinate position.

10. The apparatus of claim 8 wherein the consecutive coordinate is used as the coordinate position.

11. A method of eliminating noise from the reading of analog to digital converter signals to a touch screen comprising the steps of:

reading a first coordinate of a coordinate pair at a first time;

consecutively reading the same coordinate at a second time;

determining if the absolute value of the difference between the first coordinate and the consecutive coordinate is less than a predetermined value; and

quantifying, responsive to the difference determining step the coordinate position as a function of the first or the consecutive coordinate.

12. Apparatus eliminating noise from the reading of analog to digital converter signals to a touch screen comprising:

means for reading a first coordinate of a coordinate pair at a first time;

means for consecutively reading the same coordinate at a second time;

means for determining if the absolute value of the difference between the first coordinate and the consecutive coordinate is less than a predetermined value; and

means, response to the determining means, for quantifying the coordinate position as a function of the first or the consecutive coordinate.

13. In a touch-screen display system for generating pixel coordinate estimates responsive to a user touching a display screen, an apparatus for enabling detection of a “

no touch”

state of said touch-screen display system comprising;

at least one bus bar;

at least one driver electrically connected to said at least one bus bar to selectively switch said at least one bus bar between at least two of a plurality of electrical potentials wherein the at least one driver is selected to have an off state impedance establishing a pre-determined discharge rate.

14. In a touch-screen display system for generating pixel coordinate estimates responsive to a user touching a display screen, an apparatus for enabling detection of a “

no touch”

state of said touch-screen display system comprising;

at least one bus bar;

at least one driver electrically connected to said at least one bus bar to selectively switch said at least one bus bar between at least two of a plurality of electrical potentials wherein the at least one driver is controlled to establish pre-determined discharge rates.

15. A method of determining whether or not a touch screen has been touched comprising the steps of:

providing an analog to digital converter which supplies an analog to digital reading;

reading a maximum bit level;

determining whether the reading is smaller than the maximum bit level; and

determining the absence of a user touch if the modified reading is less than the maximum bit level.

16. The method of claim 15 wherein the reading step includes the use of a pull up resistor.

17. Apparatus determining whether or not a touch screen has been touched comprising:

means for providing an analog to digital reading from an analog to digital converter;

means for reading a maximum bit level;

means for determining whether the reading is smaller than the maximum bit level; and

means for determining the absence of a user touch if the reading is less than a maximum bit level.

18. The apparatus of claim 17 wherein the providing means includes a pull up resistor.