Electronic device validating multiple finger touch detection through donut shaped touch islands, and related methods

1. A touch screen controller operable with a touch screen, the touch screen controller comprising:

input circuitry configured to receive touch data from the touch screen; and

processing circuitry configured to:

acquire mutual capacitance touch strength values from the touch screen;

determine when the mutual capacitance touch strength values define a pre-validated donut touch pattern;

read self capacitance touch strength values for lines that are contained within bounds of the pre-validated donut touch pattern;

if the self capacitance touch strength values for lines contained within bounds of the pre-validated donut touch pattern contain a singular peak value, validate the pre-validated donut touch pattern as representing a single touch; and

if the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain multiple peak values:

identify a valley in the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern;

separate the bounds of the pre-validated donut touch pattern into two candidate donut touch patterns separated from one another by the valley;

determine whether the mutual capacitance touch strength values respectively on each of the two candidate donut touch patterns each define a newly pre-validated donut touch pattern; and

if the self capacitance touch strength values that are contained with bounds of either pre-validated donut touch pattern contain a singular peak value, validate that newly pre-validated donut touch pattern as a newly validated donut touch pattern representing a single touch.

2. The touch screen controller of claim 1 , wherein the processing circuitry is further configured to, for each newly validated donut touch pattern:

store the bounds of that newly validated donut touch pattern;

in a next frame, read new mutual capacitance touch strength values from the touch screen that are contained within bounds of the newly validated donut touch pattern; and

if the new mutual capacitance touch strength values do not represent a new pre-validated donut touch pattern:

read new self capacitance touch strength values from the touch screen that are contained within bounds of the newly validated donut touch pattern; and

if the new self capacitance touch strength values that are contained within bounds of the newly validated donut touch pattern contain a singular peak value, consider the new mutual capacitance touch strength values to indicate the newly validated donut touch pattern.

3. A touch screen controller operable with a touch screen, the touch screen controller comprising:

input circuitry configured to receive touch data from the touch screen; and

processing circuitry configured to:

acquire mutual capacitance touch strength values from the touch screen;

determine when the mutual capacitance touch strength values define a pre-validated donut touch pattern;

read self capacitance touch strength values for lines that are contained within bounds of the pre-validated donut touch pattern; and

if the self capacitance touch strength values for lines contained within bounds of the pre-validated donut touch pattern contain a singular peak value, validate the pre-validated donut touch pattern as representing a single touch;

wherein the processing circuitry is further configured to, for each validated donut touch pattern:

store the bounds of that validated donut touch pattern;

in a next frame, read new mutual capacitance touch strength values from the touch screen that are contained within bounds of the validated donut touch pattern; and

if the new mutual capacitance touch strength values do not represent a new pre-validated donut touch pattern:

read new self capacitance touch strength values from the touch screen that are contained within bounds of the validated donut touch pattern; and

if the new self capacitance touch strength values that are contained within bounds of the validated donut touch pattern contain a singular peak value, consider the new mutual capacitance touch strength values to indicate the validated donut touch pattern.

4. The touch screen controller of claim 3 , wherein the processing circuitry is further configured to: read new mutual capacitance touch strength values from the touch screen for the entire touch screen, and if the new mutual capacitance touch strength values indicate a touch outside of the validated donut touch pattern, do not consider the new mutual capacitance touch strength values to indicate the validated donut touch pattern regardless of whether those of the new self capacitance touch strength values that are contained within bounds of the validated donut touch pattern include a singular peak value.

5. The touch screen controller of claim 1 , wherein the processing circuitry is configured to, if the self capacitance touch strength values that are contained within bounds of the pre-validate donut touch pattern contain only a singular peak value and no other peak values, validate the pre-validated donut touch pattern as a validated donut touch pattern representing a single touch.

6. The touch screen controller of claim 1 , wherein the processing circuitry determines whether the self capacitance touch strength values that are contained within bounds of the pre-validate donut touch pattern contain a singular peak value or whether the self capacitance touch strength values that are contained within bounds of the pre-validate donut touch pattern contain a multiple peak values by locating self capacitance touch strength values that are substantially greater in magnitude than neighboring self capacitance touch strength values.

7. The touch screen controller of claim 1 , wherein the processing circuitry determines whether the mutual capacitance touch strength values define a pre-validated donut pattern by:

locating a touch island comprised of lower mutual capacitance touch strength values within adjacent higher mutual capacitance touch strength values; and

pre-validating the touch island to represent a pre-validated donut pattern by determining that each mutual capacitance touch strength value at a corner of bounds of the lower mutual capacitance touch strength values has a horizontal neighbor and a vertical neighbor that is substantially greater in magnitude.

8. A method, comprising:

reading mutual capacitance touch strength values from a touch screen, in a mutual capacitance sensing mode;

determining when the mutual capacitance touch strength values define a pre-validated donut touch pattern;

reading self capacitance touch strength values from the touch screen that are contained within bounds of the pre-validated donut touch pattern, in a self capacitance sensing mode;

if the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain a singular peak value, validate the pre-validated donut touch pattern as a validated donut touch pattern representing a single touch;

if the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain multiple peak values:

identifying a valley in the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern;

separating the bounds of the pre-validated donut touch pattern into two candidate donut touch patterns separated from one another by the valley;

determining whether the mutual capacitance touch strength values respectively on each of the two candidate donut touch patterns each define a newly pre-validated donut touch pattern; and

if the self capacitance touch strength values that are contained with bounds of either pre-validated donut touch pattern contain a singular peak value, validating that newly pre-validated donut touch pattern as a newly validated donut touch pattern representing a single touch.

9. The method of claim 8 , wherein, for each newly validated donut touch pattern, the method includes:

storing the bounds of that newly validated donut touch pattern;

in a next frame, reading new mutual capacitance touch strength values from the touch screen that are contained within bounds of the newly validated donut touch pattern, in the mutual capacitance sensing mode;

if the new mutual capacitance touch strength values do not represent a new pre-validated donut touch pattern:

reading new self capacitance touch strength values from the touch screen that are contained within bounds of the newly validated donut touch pattern, in the self capacitance sensing mode;

if the new self capacitance touch strength values that are contained within bounds of the newly validated donut touch pattern contain a singular peak value, considering the new mutual capacitance touch strength values to indicate the newly validated donut touch pattern.

10. A method comprising:

reading mutual capacitance touch strength values from a touch screen, in a mutual capacitance sensing mode;

determining when the mutual capacitance touch strength values define a pre-validated donut touch pattern;

reading self capacitance touch strength values from the touch screen that are contained within bounds of the pre-validated donut touch pattern, in a self capacitance sensing mode; and

if the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain a singular peak value, validate the pre-validated donut touch pattern as a validated donut touch pattern representing a single touch;

wherein, for each validated donut touch pattern, the method also includes:

storing the bounds of that validated donut touch pattern;

in a next frame, reading new mutual capacitance touch strength values from the touch screen that are contained within bounds of the validated donut touch pattern, in the mutual capacitance sensing mode; and

if the new mutual capacitance touch strength values do not represent a new pre-validated donut touch pattern:

reading new self capacitance touch strength values from the touch screen that are contained within bounds of the validated donut touch pattern, in the self capacitance sensing mode; and

if the new self capacitance touch strength values that are contained within bounds of the validated donut touch pattern contain a singular peak value, considering the new mutual capacitance touch strength values to indicate the validated donut touch pattern.

11. The method of claim 10 , wherein, if the new mutual capacitance touch strength values indicate a touch outside of the validated donut touch pattern, do not consider the new mutual capacitance touch strength values to indicate the validated donut touch pattern regardless of whether those of the new self capacitance touch strength values that are contained within bounds of the validated donut touch pattern contain a singular peak value.

12. The method of claim 8 , wherein if the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain only a singular peak value and no other peak values, the method includes validating the pre-validated donut touch pattern as a validated donut touch pattern representing a single touch.

13. The method of claim 8 , wherein the method determines whether the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain a singular peak value or whether the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain a multiple peak values by locating self capacitance touch strength values that are substantially greater in magnitude than their neighbors.

14. A method comprising:

reading mutual capacitance touch strength values from a touch screen, in a mutual capacitance sensing mode;

determining whether the mutual capacitance touch strength values define a pre-validated donut pattern by:

locating a touch island comprised of lower mutual capacitance touch strength values within adjacent higher mutual capacitance touch strength values, wherein the lower mutual capacitance touch strength values are below a given threshold and wherein the higher mutual capacitance touch strength values are above the given threshold; and

pre-validating the touch island to represent a pre-validated donut pattern by determining that each mutual capacitance touch strength value at a corner of bounds of the lower mutual capacitance touch strength values has a horizontal neighbor and a vertical neighbor that are both above the given threshold

reading self capacitance touch strength values from the touch screen that are contained within bounds of the pre-validated donut touch pattern, in a self capacitance sensing mode; and

if the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain a singular peak value, validating the pre-validated donut touch pattern as a validated donut touch pattern representing a single touch.

15. The method of claim 14 , wherein the method determines whether the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain a singular peak value or whether the self capacitance touch strength values that are contained within bounds of the pre-validated donut touch pattern contain a multiple peak values by locating self capacitance touch strength values that are substantially greater in magnitude than their neighbors.