Fast scanning for mutual capacitance screens
In one embodiment, an apparatus for detecting a touch. The apparatus includes a touch sensor that includes a first plurality of electrode lines and a second plurality of electrode lines. The apparatus also includes a touch sensor controller coupled to the touch sensor. The touch sensor controller is operable to apply a respective voltage pulse simultaneously to each of the first plurality of electrode lines, measure a respective signal at each of the second plurality of electrode lines, and detect a touch based on the measurement of the respective signals.
1. An apparatus for detecting a touch comprising:
a touch sensor comprising a first plurality of electrode lines and a second plurality of electrode lines; and
a touch sensor controller coupled to the touch sensor, the touch sensor controller operable to:
perform, in a first detecting mode, operations comprising:
applying a respective voltage pulse simultaneously to each of the first plurality of electrode lines; and
measuring a respective signal at each of the second plurality of electrode lines;
change, in response to not detecting a touch in the first detecting mode, to a second detecting mode, the touch sensing controller operable to, in the second detecting mode, perform operations comprising:
applying a respective voltage pulse simultaneously to each of the second plurality of electrode lines; and
measuring a respective signal at each of the first plurality of electrode lines;
change, in response to detecting a touch in the first or the second detecting mode, to a third detecting mode, the touch sensing controller operable to, in the third detecting mode, perform operations comprising:
applying a respective voltage pulse to each of the first plurality of electrode lines in a sequence;
measuring a respective signal at each of the second plurality of electrode lines; and
detecting a touch based on the measurement of the respective signals.
2. The apparatus of claim 1 , wherein the touch sensor controller is further operable to apply a respective voltage pulse simultaneously to each of the first plurality of electrode lines by applying:
a respective voltage pulse having a first magnitude and a first polarity to a first portion of the first plurality of electrode lines; and
a respective voltage pulse having a second magnitude and a second polarity opposite to the first polarity to a second portion of the first plurality of electrode lines.
3. The apparatus of claim 2 , wherein:
the first portion of the first plurality of electrode lines comprises a third portion of the first plurality of electrode lines and a fourth portion of the first plurality of electrode lines; and
the third portion of the first plurality of electrode lines is separated from the fourth portion of the first plurality of electrode lines by the second portion of the first plurality of electrode lines.
4. The apparatus of claim 2 , wherein the touch sensor controller is further operable to detect a touch based on either positive or negative signals.
5. The apparatus of claim 1 , wherein the touch sensor controller is further operable to apply a respective voltage pulse simultaneously to each of the first plurality of electrode lines by applying:
a respective voltage pulse having a first magnitude and a first polarity to a first portion of the first plurality of electrode lines, the first portion of the first plurality of electrode lines having a number of electrode lines, wherein the first magnitude is inversely proportional to the number of electrode lines in the first portion of the first plurality of electrode lines; and
a respective voltage pulse having a second magnitude and a second polarity opposite to the first polarity to a second portion of the first plurality of electrode lines, the second portion of the first plurality of electrode lines having a number of electrode lines, wherein the second magnitude is inversely proportional to the number of electrode lines in the second portion of the first plurality of electrode lines.
6. The apparatus of claim 1 , wherein the touch sensor controller is further operable to apply a respective voltage pulse to each of the second plurality of electrode lines in a sequence when a touch has been detected.
7. A method comprising:
performing, in a first detecting mode, operations comprising:
applying a respective voltage pulse simultaneously to each of a first plurality of electrode lines; and
measuring a respective signal at each of a second plurality of electrode lines;
changing, in response to not detecting a touch in the first detecting mode, to a second detecting mode; and
performing, in the second detecting mode, operations comprising:
applying a respective voltage pulse simultaneously to each of the second plurality of electrode lines; and
measuring a respective signal at each of the first plurality of electrode lines;
changing, in response to detecting a touch in the first or the second detecting mode, to a third detecting mode;
in the third detecting mode, perform operations comprising:
applying a respective voltage pulse to each of the first plurality of electrode lines in a sequence;
measuring a respective signal at each of the second plurality of electrode lines; and
detecting a touch based on the measurement of the respective signals.
8. The method of claim 7 , further comprising:
applying a respective voltage pulse having a first magnitude and a first polarity to a first portion of the first plurality of electrode lines; and
applying a respective voltage pulse having a second magnitude and a second polarity opposite to the first polarity to a second portion of the first plurality of electrode lines.
9. The method of claim 8 , wherein:
the first portion of the first plurality of electrode lines comprises a third portion of the first plurality of electrode lines and a fourth portion of the first plurality of electrode lines; and
the third portion of the first plurality of electrode lines is separated from the fourth portion of the first plurality of electrode lines by the second portion of the first plurality of electrode lines.
10. The method of claim 8 , further comprising detecting a touch based on either positive or negative signals.
11. The method of claim 7 , further comprising:
applying a respective voltage pulse having a first magnitude and a first polarity to a first portion of the first plurality of electrode lines, the first portion of the first plurality of electrode lines having a number of electrode lines, wherein the first magnitude is inversely proportional to the number of electrode lines in the first portion of the first plurality of electrode lines; and
applying a respective voltage pulse having a second magnitude and a second polarity opposite to the first polarity to a second portion of the first plurality of electrode lines, the second portion of the first plurality of electrode lines having a number of electrode lines, wherein the second magnitude is inversely proportional to the number of electrode lines in the second portion of the first plurality of electrode lines.
12. The method of claim 7 , further comprising applying a respective voltage pulse to each of the second plurality of electrode lines in a sequence when a touch has been detected.
13. A non-transitory computer readable medium comprising logic, the logic operable to, when executed by one or more processors, cause the one or more processors to:
perform, in a first detecting mode, operations comprising:
causing the application of a respective voltage pulse simultaneously to each of a first plurality of electrode lines; and
measuring a respective signal at each of a second plurality of electrode lines;
change, in response to not detecting a touch in the first detecting mode, to a second detecting mode, the logic, when executed by a processor, operable to, in the second detecting mode, perform operations comprising:
causing the application of a respective voltage pulse simultaneously to each of the second plurality of electrode lines; and
measuring a respective signal at each of the first plurality of electrode lines;
change, in response to detecting a touch in the first or the second detecting mode, to a third detecting mode, the logic, when executed by a processor, operable to, in the third detecting mode, perform operations comprising:
applying a respective voltage pulse to each of the first plurality of electrode lines in a sequence;
measuring a respective signal at each of the second plurality of electrode lines; and
detecting a touch based on the measurement of the respective signals.
14. The non-transitory computer readable medium of claim 13 , wherein the logic is operable to, when executed by the one or more processors, cause the one or more processors to cause the application of a respective voltage pulse simultaneously to each of the first plurality of electrode lines by causing the application of:
a respective voltage pulse having a first magnitude and a first polarity to a first portion of the first plurality of electrode lines; and
a respective voltage pulse having a second magnitude and a second polarity opposite to the first polarity to a second portion of the first plurality of electrode lines.
15. The non-transitory computer readable medium of claim 14 , wherein:
the first portion of the first plurality of electrode lines comprises a third portion of the first plurality of electrode lines and a fourth portion of the first plurality of electrode lines; and
the third portion of the first plurality of electrode lines is separated from the fourth portion of the first plurality of electrode lines by the second portion of the first plurality of electrode lines.
16. The non-transitory computer readable medium of claim 14 , wherein the logic is operable to, when executed by the one or more processors, cause the one or more processors to detect a touch based on either positive or negative signals.
17. The non-transitory computer readable medium of claim 13 , wherein the logic is operable to, when executed by the one or more processors, cause the one or more processors to cause the application of a respective voltage pulse simultaneously to each of the first plurality of electrode lines by causing the application of:
a respective voltage pulse having a first magnitude and a first polarity to a first portion of the first plurality of electrode lines, the first portion of the first plurality of electrode lines having a number of electrode lines, wherein the first magnitude is inversely proportional to the number of electrode lines in the first portion of the first plurality of electrode lines; and
a respective voltage pulse having a second magnitude and a second polarity opposite to the first polarity to a second portion of the first plurality of electrode lines, the second portion of the first plurality of electrode lines having a number of electrode lines, wherein the second magnitude is inversely proportional to the number of electrode lines in the second portion of the first plurality of electrode lines.
18. The non-transitory computer readable medium of claim 13 , wherein the logic is operable to, when executed by the one or more processors, cause the one or more processors to apply a respective voltage pulse to each of the second plurality of electrode lines in a sequence when a touch has been detected.