Multi-stage stylus detection
A system comprises a processing device and a capacitive sense array that includes a plurality of electrodes. The system receives a first signal from a first scan of electrodes in a capacitive sense array. The system processes the first signal using a first set of sequences to detect a stylus. The system receives a second scan from a second scan of electrodes in a capacitive sense array. The system processes the second signal using a second set of sequences to detect the stylus.
1. An apparatus comprising:
a sense array comprising a plurality of electrodes;
an analog-to-digital converter (ADC) coupled to the sense array and configured to receive signals from the sense array in a first mode and in a second mode; and
a processing device coupled to the sense array and to the ADC, the processing device configured at least to:
set the ADC to a first sampling frequency in the first mode;
and set the ADC to a second sampling frequency in the second mode.
2. The apparatus of claim 1 , wherein the processing device is configured to detect a stylus proximate to the sense array in the first mode.
3. The apparatus of claim 1 , wherein the processing device is configured to detect a touch object proximate to the sense array in the second mode.
4. The apparatus of claim 1 , wherein the processing device is configured to detect a stylus in the first mode concurrently with detecting a touch object in the second mode.
5. The apparatus of claim 1 , wherein the processing device is further configured to switch to the first mode in response to detecting a stylus proximate to the sense array, wherein the first mode comprises stylus only sensing.
6. The apparatus of claim 1 , wherein the processing device is further configured to switch to the second mode to detect a touch object proximate to the sense array.
7. The apparatus of claim 1 , wherein the processing device further comprises:
a first processing stream to process a first in-phase component of a first signal and a second in-phase component of a second signal; and
a second processing stream to process a first quadrature component of the first signal and a second quadrature component of the second signal.
8. The apparatus of claim 7 , wherein the first signal is received from a first scan of the sense array and the second signal is received from a second scan of the sense array.
9. The apparatus of claim 8 , wherein the first scan of the sense array and the second scan of the sense array are used in the first mode to detect a stylus proximate to the sense array.
10. The apparatus of claim 8 , wherein the first scan of the sense array and the second scan of the sense array are used in the second mode to detect a touch object proximate to the sense array.
11. A method comprising:
setting an analog-to-digital converter (ADC) to a first sampling frequency in a first mode, wherein the ADC is coupled to a sense array that comprises a plurality of electrodes;
receiving a first plurality of signals from the sense array in the first mode;
setting the ADC to a second sampling frequency in a second mode; and
receiving a second plurality of signals from the sense array in the second mode.
12. The method of claim 11 , further comprising detecting a stylus proximate to the sense array in the first mode based on the first plurality of signals.
13. The method of claim 11 , further comprising detecting a touch object proximate to the sense array in the second mode based on the second plurality of signals.
14. The method of claim 11 , further comprising detecting a stylus in the first mode concurrently with detecting a touch object in the second mode.
15. The method of claim 11 , further comprising switching to the first mode in response to detecting a stylus proximate to the sense array, wherein the first mode comprises stylus only sensing.
16. The method of claim 11 , further comprising switching to the second mode to detect a touch object proximate to the sense array.
17. The method of claim 11 , further comprising:
processing, in a first stream, a first in-phase component of a first signal and a second in-phase component of a second signal; and
processing, in a second stream, a first quadrature component of the first signal and a second quadrature component of the second signal.
18. The method of claim 17 , wherein the first signal is received from a first scan of the sense array and the second signal is received from a second scan of the sense array.
19. The method of claim 18 , further comprising using, in the first mode, the first scan of the sense array and the second scan of the sense array to detect a stylus proximate to the sense array.
20. The method of claim 18 , further comprising using, in the second mode, the first scan of the sense array and the second scan of the sense array to detect a touch object proximate to the sense array.
21. An apparatus comprising:
an analog-to-digital converter (ADC) coupled to a sense array comprising a plurality of electrodes and configured to receive signals from the sense array in a first mode and in a second mode; and
a processing device coupled to the sense array and to the ADC, the processing device configured at least to:
set the ADC to a first sampling frequency in the first mode; and
set the ADC to a second sampling frequency in the second mode,
wherein the processing device is configured to conduct switching between the first mode and the second mode, each mode relating to a frequency of a transmission signal transmitted from a stylus detected through the sense array.
22. An method comprising:
setting an analog-to-digital converter (ADC) to a first sampling frequency in a first mode, wherein the ADC is coupled to a sense array that comprises a plurality of electrodes;
receiving a first plurality of signals from the sense array in the first mode;
setting the ADC to a second sampling frequency in a second mode;
receiving a second plurality of signals from the sense array in the second mode; and
switching between the first mode and the second mode, wherein the switching between the first mode and the second mode corresponds to a frequency of a transmission signal transmitted from a stylus detected through the sense array.