Processing analog to digital converter signals to a touch screen display
View Patent ↗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.
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.