Multi-touch integrity sensing for capacitive touch screen
A method for multi-touch integrity sensing for a multi-touch capacitive touch screen is disclosed. By determining the integrity of touches, a distinction is identified between wanted touches, such as via a finger or stylus, and unwanted touches such as via foreign matter, errors, and the like.
1. A method, comprising:
identifying mutual touch islands, wherein each mutual touch island contains certain mutual capacitance nodes of a capacitive sensing panel;
identifying self-capacitance touched nodes of the capacitive sensing panel along a first axis of the capacitive sensing panel;
identifying self-capacitance touched nodes of the capacitive sensing panel along a second axis of the capacitive sensing panel; and
confirming integrity of the mutual touch islands if:
a) a maximum number of the identified self-capacitance touched nodes along the first or second axes is less than or equal to a count of the identified mutual touch islands; and
b) the count of the identified mutual touch islands is less than or equal to a peak area, wherein the peak area is equal to the number of the identified self-capacitance touched nodes along the first axis multiplied by the number of the identified self-capacitance touched nodes along the second axis.
2. The method of claim 1 , further comprising, if integrity of the mutual touch islands is not confirmed, then:
for each mutual touch island, summing mutual capacitance strength values for said certain mutual capacitance nodes included in the mutual touch island;
determining if the sum of the mutual capacitance strength values exceeds a threshold;
if yes, confirming integrity of that mutual touch island.
3. The method of claim 2 , further comprising identifying a range for a number of detected mutual touch islands that is greater than or equal to the maximum number of the identified self-capacitance touched nodes along the first or second axes but less than or equal to the peak area.
4. A method, comprising:
identifying touch islands detected using a mutual capacitance sensing operation;
identifying first touch nodes detected using a self-capacitance sensing operation along a first sensing axis;
identifying second touch nodes detected using the self-capacitance sensing operation along a second sensing axis; and
confirming integrity of the identified touch islands if:
a) a count of the identified mutual touch islands is greater than or equal to a maximum of the number of identified first or second touch nodes; and
b) the count of the identified mutual touch islands is less than or equal to a peak area, wherein the peak area is equal to the product of the number of first touch nodes and second touch nodes.
5. The method of claim 4 , further comprising, if integrity of the touch islands is not confirmed, the confirming the integrity of each touch island if strength of the touch island exceeds a threshold.
6. The method of claim 5 , further comprising identifying a range for a number of detected touch islands that is greater than or equal to maximum of the number of identified first or second touch nodes but less than or equal to the peak area.