Enhanced mutual capacitance touch screen display with shape detection and methods for use therewith
A capacitive touch screen display operates by: receiving a plurality of sensed signals indicating variations in mutual capacitance associated with a plurality of cross points formed by a plurality of electrodes; generating capacitance image data associated with the plurality of cross points that includes positive capacitance variation data corresponding to positive variations of the capacitance image data from a nominal value and negative capacitance variation data corresponding to negative variations of the capacitance image data from the nominal value; and processing the positive capacitive data and the negative capacitance data to determine a shape of an object on the touch screen display.
1. A touch screen display comprises:
a display configured to render frames of data into visible images;
a plurality of electrodes integrated into the display to facilitate touch sense functionality based on electrode signals having a drive signal component and a receive signal component, wherein the plurality of electrodes includes a plurality of row electrodes and a plurality of column electrodes, wherein the plurality of row electrodes is separated from the plurality of column electrodes by a dielectric material and wherein the plurality of row electrodes and the plurality of row electrodes form a plurality of cross points;
a plurality of drive-sense circuits coupled to at least some of the plurality of electrodes to generate a plurality of sensed signals, wherein each the plurality of drive-sense circuits includes a first conversion circuit and a second conversion circuit, and wherein, when a drive-sense circuit of the plurality of drive-sense circuits is enabled to monitor a corresponding electrode of the plurality of electrodes, the first conversion circuit is configured to convert the receive signal component into a sensed signal of the plurality of sensed signals and the second conversion circuit is configured to generate the drive signal component from the sensed signal of the plurality of sensed signals;
a processing module that includes at least one memory that stores operational instructions and at least one processing circuit that executes the operational instructions to perform operations that include:
receiving the plurality of sensed signals, wherein the sensed signals indicate variations in mutual capacitance associated with the plurality of cross points;
generating based on the plurality of sensed signals, capacitance image data associated with the plurality of cross points that includes positive capacitance variation data corresponding to positive variations of the capacitance image data from a nominal value and negative capacitance variation data corresponding to negative variations of the capacitance image data from the nominal value; and
processing the positive capacitance variation data and the negative capacitance variation data to determine a shape of an object on the touch screen display.
2. The touch screen display of claim 1 , wherein the operations further include:
identifying noise in the capacitance image data based on the positive capacitance variation data, and the negative capacitance variation data;
determining, based on the noise in the capacitance image data, an upper threshold and a lower threshold;
generating compensated capacitance image data, based on the upper threshold and the lower threshold, to compensate for the noise in the capacitance image data; and
wherein processing the positive capacitive data and the negative capacitance data to determine a shape of an object on the touch screen display is based on the compensated capacitance image data.
3. The touch screen display of claim 2 , wherein a region between the upper threshold and the lower threshold corresponds to a noise zone, and wherein generating the compensated capacitance image data includes ignoring portions of the capacitance image data within the noise zone.
4. The touch screen display of claim 2 , wherein a region between the upper threshold and the lower threshold corresponds to a noise zone, and wherein generating the compensated capacitance image data includes removing portions of the capacitance image data within the noise zone.
5. The touch screen display of claim 2 , wherein a region between the upper threshold and the lower threshold corresponds to a noise zone, and wherein generating the compensated capacitance image data includes subtracting portions of the capacitance image data within the noise zone.
6. The touch screen display of claim 1 , wherein the operations further include:
identifying a proximal touch condition of the touch screen display based on the positive capacitance variation data.
7. The touch screen display of claim 6 , wherein identifying the proximal touch condition includes a proximal touch of the touch screen display by a finger.
8. The touch screen display of claim 1 , wherein the variations in mutual capacitance associated the plurality of cross points vary positively and negatively from a nominal mutual capacitance.
9. The touch screen display of claim 8 , wherein the nominal mutual capacitance corresponds to an average mutual capacitance of the plurality of cross points in a non-touch condition of the touch screen display.
10. The touch screen display of claim 1 , wherein the sensed signals indicate an impedance of the plurality of cross points.
11. The touch screen display of claim 1 , wherein the nominal value is proportional to a nominal impedance corresponding to each of the cross points of the plurality of cross points in a non-touch condition of the touch screen display.
12. The touch screen display of claim 1 ,
wherein the first conversion circuit includes:
a comparator to compare the electrode signal to an analog reference signal to produce an analog comparison signal; and
an analog to digital converter operable to convert the analog comparison signal into the sensed signal; and
wherein the second conversion circuit includes:
a digital to analog converter operable to convert the sensed signal into an analog feedback signal;
a signal source circuit operable to generate a regulated source signal based on the analog feedback signal; and
a driver operable to increase power of the regulated source signal to produce the drive signal component.
13. The touch screen display of claim 1 , wherein the first conversion circuit is configured to generate the receive signal component from the sensed signal via an analog error signal that is based on a difference between a reference signal and a first analog signal, and wherein the second conversion circuit is configured to generate the drive signal component from the sensed signal via a second analog signal based on the analog error signal.
14. A method for use in a touch screen display comprises:
providing a display configured to render frames of data into visible images;
providing a plurality of electrodes integrated into the display to facilitate touch sense functionality based on electrode signals having a drive signal component and a receive signal component, wherein the plurality of electrodes includes a plurality of row electrodes and a plurality of column electrodes, wherein the plurality of row electrodes is separated from the plurality of column electrodes by a dielectric material and wherein the plurality of row electrodes and the plurality of row electrodes form a plurality of cross points;
generating, via a plurality of drive-sense circuits coupled to at least some of the plurality of electrodes, a plurality of sensed signals, wherein each the plurality of drive-sense circuits includes a first conversion circuit and a second conversion circuit, and wherein, when a drive-sense circuit of the plurality of drive-sense circuits is enabled to monitor a corresponding electrode of the plurality of electrodes, the first conversion circuit is configured to convert the receive signal component into a sensed signal of the plurality of sensed signals and the second conversion circuit is configured to generate the drive signal component from the sensed signal of the plurality of sensed signals;
receiving, at a processing module that includes at least one memory and at least one processing circuit, the plurality of sensed signals, wherein the sensed signals indicate variations in mutual capacitance associated with the plurality of cross points;
generating, via the processing module and based on the plurality of sensed signals, capacitance image data associated with the plurality of cross points that includes positive capacitance variation data corresponding to positive variations of the capacitance image data from a nominal value and negative capacitance variation data corresponding to negative variations of the capacitance image data from the nominal value;
processing the positive capacitance variation data and the negative capacitance variation data to determine a shape of an object on the touch screen display.
15. The method of claim 14 , further comprising:
identifying a proximal touch condition of the touch screen display based on the positive capacitance variation data.
16. The method of claim 15 , wherein identifying the proximal touch condition includes a proximal touch of the touch screen display by a finger.
17. The method of claim 14 , wherein the variations in mutual capacitance associated the plurality of cross points vary positively and negatively from a nominal mutual capacitance.
18. The method of claim 17 , wherein the nominal mutual capacitance corresponds to an average mutual capacitance of the plurality of cross points in a non-touch condition of the touch screen display.
19. The method of claim 14 , wherein the sensed signals indicate an impedance of the plurality of cross points.
20. The method of claim 14 , wherein the nominal value is proportional to a nominal impedance corresponding to each of the cross points of the plurality of cross points in a non-touch condition of the touch screen display.