Transmitter axis projection construction for capacitive sensing

1. A processing system comprising:

sensor circuitry configured to be coupled to a plurality of transmitter electrodes and a plurality of receiver electrodes associated with a sensing region, the sensor circuitry configured to:

drive the plurality of transmitter electrodes with first transmitter signals and receive first resulting signals from the plurality of receiver electrodes,

wherein the plurality of transmitter electrodes comprises a first transmitter electrode and a second transmitter electrode, and

drive only a first subset of the plurality of receiver electrodes with second transmitter signals and receive second resulting signals with the plurality of transmitter electrodes,

wherein the first subset comprises a first receiver electrode and a second receiver electrode; and

processing circuitry connected to the sensor circuitry and configured to:

generate a capacitive image of the sensing region from the first resulting signals,

partition, using the capacitive image, the plurality of receiver electrodes into the first subset of receiver electrodes and a second subset of receiver electrodes, and

generate a transmitter axis projection from the second resulting signals by:

determining a single value for the first transmitter electrode based on transcapacitive values between the first transmitter electrode and both the first receiver electrode and the second receiver electrode; and

determining a single value for the second transmitter electrode based on transcapacitive values between the second transmitter electrode and both the first receiver electrode and the second receiver electrode.

2. The processing system of claim 1 , wherein each of the first subset of the plurality of receiver electrodes is driven with the same transmitter signal concurrently, and wherein the first receiver electrode is adjacent to the second receiver electrode.

3. The processing system of claim 1 , wherein the processing circuitry is further configured to:

determine positional information from the transmitter axis projection, and

report the positional information.

4. The processing system of claim 3 , wherein determining positional information comprises using the transmitter axis projection to mitigate for effects of moisture on an input surface of the sensing region.

5. The processing system of claim 3 , wherein determining positional information comprises using the transmitter axis projection to mitigate for effects of interference.

6. A method comprising:

driving a plurality of transmitter electrodes with first transmitter signals and receive first resulting signals from a plurality of receiver electrodes,

wherein the plurality of transmitter electrodes comprises a first transmitter electrode and a second transmitter electrode, and

wherein the plurality of transmitter electrodes and the plurality of receiver electrodes are associated with a sensing region;

generate a capacitive image of the sensing region from the first resulting signals;

partitioning, using the capacitive image, the plurality of receiver electrodes into a first subset of receiver electrodes and a second subset of receiver electrodes,

wherein the first subset comprises a first receiver electrode and a second receiver electrode;

driving only the first subset of the plurality of receiver electrodes with second transmitter signals and receive second resulting signals with the plurality of transmitter electrodes; and

generating a transmitter axis projection from the second resulting signals by:

determining a single value for the first transmitter electrode based on transcapacitive values between the first transmitter electrode and both the first receiver electrode and the second receiver electrode; and

determining a single value for the second transmitter electrode based on transcapacitive values between the second transmitter electrode and both the first receiver electrode and the second receiver electrode.

7. The method of claim 6 , wherein each of the first subset of the plurality of receiver electrodes is driven with the same transmitter signal concurrently, and wherein the first receiver electrode is adjacent to the second receiver electrode.

8. The method of claim 6 , further comprising:

determining positional information from the transmitter axis projection, and

reporting the positional information.

9. The method of claim 8 , wherein determining positional information comprises using the transmitter axis projection to mitigate for effects of moisture on an input surface of the sensing region.

10. The method of claim 8 , wherein determining positional information comprises using the transmitter axis projection to mitigate for effects of interference.

11. An input device comprising:

a plurality of transmitter electrodes associated with a sensing region and comprising a first transmitter electrode and a second transmitter electrode;

a plurality of receiver electrodes associated with sensing region; and

processing system comprising circuitry for:

driving the plurality of transmitter electrodes with first transmitter signals and receive first resulting signals from the plurality of receiver electrodes;

generating a capacitive image of the sensing region from the first resulting signals;

partitioning, using the capacitive image, the plurality of receiver electrodes into a first subset of receiver electrodes and a second subset of receiver electrodes,

wherein the first subset comprises a first receiver electrode and a second receiver electrode;

driving only the first subset of the plurality of receiver electrodes with second transmitter signals and receive second resulting signals with the plurality of transmitter electrodes; and

generating a transmitter axis projection from the second resulting signals by:

determining a single value for the first transmitter electrode based on transcapacitive values between the first transmitter electrode and both the first receiver electrode and the second receiver electrode; and

determining a single value for the second transmitter electrode based on transcapacitive values between the second transmitter electrode and both the first receiver electrode and the second receiver electrode.

12. The input device of claim 11 , wherein each of the first subset of the plurality of receiver electrodes is driven with the same transmitter signal concurrently, and wherein the first receiver electrode is adjacent to the second receiver electrode.

13. The input device of claim 11 , the circuitry further for:

determining positional information from the transmitter axis projection, and

reporting the positional information.

14. The input device of claim 13 , wherein determining positional information comprises using the transmitter axis projection to mitigate for effects of moisture on an input surface of the sensing region.

15. The processing system of claim 1 , wherein:

determining the single value for the first transmitter electrode comprises:

obtaining a first transcapacitive value between the first receiver electrode and the first transmitter electrode,

obtaining a second transcapacitive value between the second receiver electrode and the first transmitter electrode, and

calculating a first sum based on the first transcapacitive value and the second transcapacitive value, and

determining the single value for the second transmitter electrode comprises:

obtaining a third transcapacitive value between the first receiver electrode and the second transmitter electrode,

obtaining a fourth transcapacitive value between the second receiver electrode and the second transmitter electrode, and

calculating a second sum based on the third transcapacitive value and the fourth transcapacitive value.

16. The processing system of claim 1 , wherein driving only the first subset comprises driving the first receiver electrode and the second receiver electrode concurrently using code division multiplexing.

17. The method of claim 6 , wherein:

determining the single value for the first transmitter electrode comprises:

obtaining a first transcapacitive value between the first receiver electrode and the first transmitter electrode,

obtaining a second transcapacitive value between the second receiver electrode and the first transmitter electrode, and

calculating a first sum based on the first transcapacitive value and the second transcapacitive value, and

determining the single value for the second transmitter electrode comprises:

obtaining a third transcapacitive value between the first receiver electrode and the second transmitter electrode,

obtaining a fourth transcapacitive value between the second receiver electrode and the second transmitter electrode, and

calculating a second sum based on the third transcapacitive value and the fourth transcapacitive value.