Location sensing system and method employing adaptive drive signal adjustment
Systems and methods provide for adaptive drive signal adjustment to improve reception of a stylus signal at a location sensor. A location sensing system includes an untethered stylus comprising circuitry configured to receive a drive signal and transmit a stylus signal. The circuitry is configured to be energized by the received drive signal and includes frequency-sensitive circuitry. A location sensor includes a controller and a sensing array. The location sensor is configured to generate the drive signal and receive the stylus signal. The controller is configured to adjust a parameter of the drive signal that improves receptivity of the stylus signal by the location sensor.
1. A location sensor system, comprising:
an untethered stylus comprising circuitry configured to receive a drive signal and transmit a stylus signal, the circuitry configured to be energized by the received drive signal and comprising frequency-sensitive circuitry; and
a location sensor comprising a controller and sensing array, the location sensor configured to generate the drive signal and receive the stylus signal, the controller configured to adjust a parameter of the drive signal that improves receptivity of the stylus signal by the location sensor; wherein
the controller is configured to:
adjust the frequency of the drive signal to switch back and forth between frequencies higher and lower than an estimated resonance frequency of the frequency-sensitive circuitry;
determine a magnitude of the stylus signal at each of the adjusted drive signal frequencies; and
adjust the drive signal frequency in a manner that increases the stylus signal magnitude.
2. The system of claim 1 , wherein the controller is configured to adjust a parameter of the drive signal that increases a magnitude of the stylus signal.
3. The system of claim 1 , wherein the controller is configured to adjust a parameter of the drive signal that modifies a phase of the stylus signal.
4. The system of claim 1 , wherein the controller is configured to adjust a parameter of the drive signal that increases a signal-to-noise ratio of the stylus signal.
5. The system of claim 1 , wherein the controller is configured to measure a parameter of the stylus signal as the drive signal parameter is adjusted over a range of parameter values.
6. The system of claim 5 , wherein the stylus signal parameter is a magnitude of the stylus signal.
7. The system of claim 5 , wherein the stylus signal parameter is a phase of the stylus signal.
8. The system of claim 1 , wherein the controller is configured to adjust a frequency of the drive signal to match a resonance frequency of the frequency-sensitive circuitry of the stylus.
9. The system of claim 1 , wherein the controller is configured to adjust a frequency of the drive signal to track changes of a resonance frequency of the frequency-sensitive circuitry of the stylus.
10. The system of claim 1 , wherein the controller is configured to:
determine a location of the stylus relative to the sensing array based on absolute values of stylus signal magnitudes at both higher and lower frequencies.
11. The system of claim 1 , wherein the stylus circuitry is configured to modulate the magnitude of the stylus signals at the higher and lower frequencies in a predetermined frequency or code sequence, and the controller further configured to demodulate the predetermined frequency or code sequence as a stylus status indication.
12. The system of claim 1 , wherein a resonance frequency of the frequency-sensitive circuitry of the stylus changes in accordance with a status change of the stylus, and the controller is configured to detect the change in stylus status by measuring a change of the drive signal frequency needed to match the resonance frequency of the frequency-sensitive circuitry.
13. The system of claim 12 , wherein the controller is configured to detect the change in stylus status by measuring a rate of change of the drive signal frequency.
14. The system of claim 1 , wherein the stylus comprises switch circuitry coupled to the frequency-sensitive circuitry and comprising one or more switches actuatable by a user of the stylus, a resonance frequency of the frequency-sensitive circuitry changing in response to actuation of the one or more switches, and the controller configured to adjust a frequency of the drive signal to match the changed resonance frequency of the frequency-sensitive circuitry.
15. The system of claim 14 , wherein the one or more switches correspond to one or more of a user-initiateable function, a mouse function, a stylus pressure measurement, and a stylus tip switch function.
16. The system of claim 1 , wherein the location sensor comprises:
a modulator configured to modulate the drive signal at a drive signal frequency corresponding to a resonance frequency of the frequency-sensitive circuitry of the stylus; and
a demodulator that is synchronized with the drive signal frequency.
17. The system of claim 1 , wherein the controller is configured to coordinate simultaneous transmission of the drive signal and reception of stylus signal.
18. A method of controlling an operating frequency of a location sensor with an untethered stylus, comprising:
receiving, at the stylus, a drive signal generated at the location sensor;
energizing the stylus and producing a signal at the stylus in response to receiving the drive signal;
receiving the stylus signal at the location sensor; and
adjusting a parameter of the drive signal that improves receptivity of the stylus signal at the location sensor; wherein
adjusting the parameter of the drive signal comprises: adjusting the frequency of the drive signal to switch back and forth between frequencies higher and lower than an estimated resonance frequency of frequency-sensitive circuitry of the stylus;
determining a magnitude of the stylus signal at each of the adjusted drive signal frequencies; and
adjusting the drive signal frequency in a manner that increases the stylus signal magnitude.
19. The method of claim 18 , wherein adjusting the parameter of the drive signal increases a magnitude of the stylus signal.
20. The method of claim 18 , wherein adjusting the parameter of the drive signal modifies a phase of the stylus signal.
21. The method of claim 18 , wherein adjusting the parameter of the drive signal increases a signal-to-noise ratio of the stylus signal.
22. The method of claim 18 , further comprising measuring a parameter of the stylus signal as the drive signal parameter is adjusted over a range of parameter values, the stylus signal parameter comprising at least one of a magnitude of the stylus signal and a phase of the stylus signal.
23. The method of claim 18 , wherein adjusting the parameter of the drive signal comprises adjusting a frequency of the drive signal to match a resonance frequency of frequency-sensitive circuitry of the stylus.
24. The method of claim 18 , wherein adjusting the parameter of the drive signal comprises tracking changes of a resonance frequency of frequency-sensitive circuitry of the stylus.
25. The method of claim 18 , wherein adjusting the parameter of the drive signal comprises:
determining a location of the stylus relative to the location sensor based on absolute values of stylus signal magnitudes at both higher and lower frequencies.
26. The method of claim 18 , wherein adjusting the parameter of the drive signal comprises:
modulating the magnitude of the stylus signals at the higher and lower frequencies in a predetermined frequency or code sequence; and
demodulating, at the location sensor, the predetermined frequency or code sequence as a stylus status indication.
27. The method of claim 18 , further comprising:
changing a resonance frequency of frequency-sensitive circuitry of the stylus in accordance with a status change of the stylus; and
detecting, at the location sensor, the change in stylus status by measuring one or both of a change and a rate of change of the drive signal frequency needed to match the resonance frequency of the frequency-sensitive circuitry of the stylus.
28. The method of claim 18 , wherein transmitting the drive signal and receiving the stylus signal at the location sensor are effected simultaneously.