Multi-touch disambiguation
A capacitance sensing method may include performing a first scan of a plurality of sensor elements of a touch-sensing surface to detect a plurality of capacitance values indicating a presence of multiple contacts at the touch sensing surface. Based on the plurality of capacitance values, a plurality of coordinates may be calculated that indicate a plurality of possible contact locations for the multiple contacts. In response to detecting that the plurality of coordinates indicates the presence of the multiple contacts, a resolve scan of at least a first intersection of sensor elements may be performed, where the first intersection corresponds to at least one of the possible contact locations. Based on the resolve scan, at least one of the possible contact locations may be identified as an actual contact location of one of the multiple contacts.
1. A method, comprising:
performing a first scan cycle of a plurality of sensor elements of a touch-sensing surface to detect a plurality of capacitance values indicating a presence of multiple contacts at the touch sensing surface;
based on the plurality of capacitance values, calculating a plurality of coordinates indicating a plurality of possible contact locations for the multiple contacts;
in response to detecting that the plurality of coordinates indicates the presence of the multiple contacts, selecting a first intersection of a pair of sensor elements of the plurality of sensor elements, the pair of sensor elements each having capacitance values affected by the presence of at least one of the multiple contacts, wherein the first intersection corresponds to a first possible contact location of the possible contact locations;
after selecting the first intersection and prior to measuring a capacitance value of any of the plurality of sensor elements having a capacitance value that is unaffected by the presence of the at least one of the multiple contacts, performing a resolve scan cycle of the selected first intersection of sensor elements to measure one or more capacitance values by sensing the selected first intersection; and
determining whether a second possible contact location different from the first contact location is an actual contact location
based on the one or more capacitance values measured from the selected first intersection during the resolve scan cycle, and
prior to sensing an intersection corresponding to the second possible contact location after sensing of the selected first intersection during the resolve scan cycle.
2. The method of claim 1 , wherein the plurality of capacitance values comprises a self-capacitance value for each of the plurality of sensor elements, wherein performing the first scan cycle comprises measuring the self-capacitance value for each of the plurality of sensor elements, and wherein performing the resolve scan cycle comprises measuring a mutual capacitance between the sensor elements intersecting at the first intersection.
3. The method of claim 1 , wherein performing the resolve scan cycle further comprises measuring a capacitance for a second intersection of sensor elements of the plurality of sensor elements, and wherein the second intersection of sensor elements shares one sensor element in common with the first intersection.
4. The method of claim 3 wherein identifying the at least one of the possible contact locations as the actual contact location comprises:
comparing a first capacitance value measured from the first intersection with a second capacitance value measured from the second intersection; and
identifying the actual contact location based on the comparing.
5. The method of claim 4 , wherein identifying the actual contact location based on the comparing further comprises identifying as the actual contact location the possible contact location corresponding the intersection, of the first intersection and the second intersection, having a higher capacitance value.
6. The method of claim 1 , wherein identifying the at least one of the possible contact locations as the actual contact location comprises:
comparing a first capacitance value measured from the first intersection with one or more of the plurality of capacitance values from the first scan cycle; and
identifying the actual contact location based on the comparing.
7. The method of claim 1 , wherein performing the resolve scan cycle further comprises measuring a capacitance for one or more sensor elements adjacent to the first intersection.
8. The method of claim 1 , further comprising:
determining, based on the plurality of capacitance values, that two or more of the possible contact locations are aligned in the same direction as an axis of one or more of the plurality of sensor elements; and
in response to determining that the two or more of the possible contact locations are aligned, identifying each of the two or more possible contact locations as actual contact locations.
9. An apparatus, comprising:
an interface configured to receive signals representative of a plurality of capacitance values measured from a plurality of capacitive sensor elements of a touch-sensing surface, wherein the plurality of capacitance values indicates a presence of multiple contacts at the touch-sensing surface; and
a processing logic coupled with the interface, wherein the processing logic is configured to:
based on the plurality of capacitance values, calculate a plurality of coordinates indicating a plurality of possible contact locations for the multiple contacts;
in response to receiving the plurality of calculated coordinates, select a first intersection a pair of sensor elements of the plurality of sensor elements, the pair of sensor elements each having capacitance values affected by the presence of at least one of the multiple contacts, wherein the first intersection corresponds to a first possible contact location of the possible contact locations;
after selecting the first intersection and prior to measuring a capacitance value of any of the plurality of sensor elements having a capacitance value that is unaffected by the presence of the at least one of the multiple contacts, perform a resolve scan cycle of the selected first intersection of sensor elements to measure one or more capacitance values by sensing the selected first intersection; and
determine whether a second possible contact location different from the first contact location is an actual contact location
based on the one or more capacitance values measured from the selected first intersection during the resolve scan cycle, and
prior to sensing an intersection corresponding to the second possible contact location after sensing of the selected first intersection during the resolve scan cycle.
10. The apparatus of claim 9 , wherein the plurality of capacitance values comprises a self-capacitance value for each of the plurality of sensor elements, wherein the apparatus further comprises a capacitance sensor coupled with the processing logic, and wherein the capacitance sensor is configured to:
perform the first scan cycle by measuring the self-capacitance value for each of the plurality of sensor elements, and
perform the resolve scan cycle by measuring a mutual capacitance between sensor elements intersecting at the first intersection.
11. The apparatus of claim 9 , further comprising a capacitance sensor coupled with the processing logic, wherein the capacitance sensor is configured to perform the resolve scan cycle by measuring a first capacitance value from the first intersection and measuring a second capacitance value from a second intersection of sensor elements of the plurality of sensor elements, wherein the second intersection of sensor elements shares a sensor element in common with the first intersection.
12. The apparatus of claim 11 , wherein the processing logic is further configured to identify the at least one of the possible contact locations as the actual contact location by:
comparing the first capacitance value with the second capacitance value; and
identifying as the actual contact location the possible contact location corresponding the intersection, of the first intersection and the second intersection, having a higher capacitance value.
13. The apparatus of claim 9 , wherein the processing logic is further configured to identify the at least one of the possible contact locations as the actual contact location by:
comparing a first capacitance value measured from the first intersection with one or more of the plurality of capacitance values from the first scan cycle; and
identifying the actual contact location based on the comparing.
14. The apparatus of claim 9 , wherein the processing logic is further configured to perform the resolve scan cycle by additionally measuring a capacitance for one or more sensor elements adjacent to the first intersection.
15. The apparatus of claim 9 , wherein the processing logic is further configured to:
determine, based on the plurality of capacitance values, that two or more of the possible contact locations are aligned in the same direction as an axis of one or more of the plurality of sensor elements; and
in response to determining that the two or more of the possible contact locations are aligned, identify each of the two or more possible contact locations as actual contact locations.
16. A capacitance sensing system, comprising:
a touch-sensing surface comprising a plurality of capacitive sensor elements;
a capacitance sensor coupled with the plurality of capacitive sensor elements, wherein the capacitance sensor is configured to perform a first scan cycle of a plurality of sensor elements of a touch-sensing surface to detect a plurality of capacitance measurements indicating a presence of multiple contacts at the touch sensing surface;
an interface configured to receive signals representative of the plurality of capacitance measurements; and
a processing logic coupled with the interface, wherein the processing logic is configured to:
calculate a plurality of coordinates indicating a plurality of possible contact locations for the multiple contacts;
in response to receiving the plurality of coordinates, select a first intersection of a pair of sensor elements of the plurality of sensor elements, the pair of sensor elements each having capacitance values affected by the presence of at least one of the multiple contacts during the first scan cycle, wherein the first intersection corresponds to a first possible contact location of the plurality of possible contact locations;
after selecting the first intersection and prior to measuring a capacitance value of any of the plurality of sensor elements having a capacitance value that is unaffected by the presence of the at least one of the multiple contacts during the first scan cycle, perform a resolve scan cycle of the selected first intersection of sensor elements to measure one or more capacitance values by sensing the selected first intersection; and
determine whether a second possible contact location different from the first contact location is an actual contact location
based on the one or more capacitance values measured from the selected first intersection during the resolve scan cycle, and
prior to sensing an intersection corresponding to the second possible contact location after sensing of the selected first intersection during the resolve scan cycle.
17. The capacitance sensing system of claim 16 , wherein the plurality of capacitance values comprises a self-capacitance value for each of the plurality of sensor elements, wherein the capacitance sensing system further comprises a capacitance sensor coupled with the processing logic, and wherein the capacitance sensor is configured to:
perform the first scan cycle by measuring the self-capacitance value for each of the plurality of sensor elements, and
perform the resolve scan cycle by measuring a mutual capacitance between sensor elements intersecting at the first intersection.
18. The capacitance sensing system of claim 16 , further comprising a capacitance sensor coupled with the processing logic, wherein the capacitance sensor is configured to perform the resolve scan cycle by measuring a first capacitance value from the first intersection and measuring a second capacitance value from a second intersection of sensor elements of the plurality of sensor elements, wherein the second intersection of sensor elements shares a sensor element in common with the first intersection.
19. The capacitance sensing system of claim 18 , wherein the processing logic is further configured to identify the at least one of the possible contact locations as the actual contact location by:
comparing the first capacitance value with the second capacitance value; and
identifying as the actual contact location the possible contact location corresponding the intersection, of the first intersection and the second intersection, having a higher capacitance value.
20. The capacitance sensing system of claim 16 , wherein the processing logic is further configured to identify the at least one of the possible contact locations as the actual contact location by:
comparing a first capacitance value for the first intersection with one or more of the plurality of capacitance values from the first scan cycle; and
identifying the actual contact location based on the comparing.