Low-power and low-frequency data transmission for stylus and associated signal processing
In one embodiment, a controller includes one or more computer-readable non-transitory storage media embodying logic that is operable when executed to: initiate an acquisition of a first signal from an electrode of a touch sensor according to an acquisition frequency of the touch sensor, store a first modulated signal which includes a modulated form of the first signal, initiate an acquisition of a second signal from the electrode of the touch sensor according to the acquisition frequency of the touch sensor, reverse a polarity of the second signal to produce a third signal, store a second modulated signal which includes a modulated form of the third signal, generate a signal-timing waveform based on the first and second modulated signals, and retrieve information associated with a stylus from the generated signal-timing waveform.
1. A controller comprising:
one or more computer-readable non-transitory storage media embodying logic that is operable when executed to:
initiate an acquisition of a first signal from an electrode of a touch sensor according to an acquisition frequency of the touch sensor;
store a first modulated signal, wherein the first modulated signal comprises a modulated form of the first signal;
initiate an acquisition of a second signal from the electrode of the touch sensor according to the acquisition frequency of the touch sensor;
reverse a polarity of the second signal, received in response to initiating the acquisition of the second signal from the electrode of the touch sensor according to the acquisition frequency of the touch sensor, to produce a third signal;
store a second modulated signal, wherein the second modulated signal comprises a modulated form of the third signal;
generate a signal-timing waveform based on the first and second modulated signals; and
retrieve, from the generated signal-timing waveform, information associated with a stylus.
2. The controller of claim 1 , wherein:
the first signal is associated with a first transmission from the stylus;
the first modulated signal is stored at an end of the acquisition of the first signal;
the first signal is modulated by one or more third-party signals during the acquisition of the first signal;
the second signal is associated with a second transmission from the stylus;
the second modulated signal is stored at an end of the acquisition of the second signal;
the third signal is modulated by the one or more third-party signals during the acquisition of the second signal;
the signal-timing waveform is generated based on subtracting the second modulated signal from the first modulated signal;
the generated signal-timing waveform substantially suppresses the one or more third-party signals; and
the generated signal-timing waveform is based on the first and second signals.
3. The controller of claim 1 , wherein the stylus is a passive stylus having a signal activator input.
4. The controller of claim 3 , wherein the information associated with the passive stylus comprises a state of the signal activator input.
5. The controller of claim 1 , wherein the information associated with the stylus comprises one or more of:
a proximity of the stylus from the touch sensor; and
a position of the stylus's projection onto the touch sensor.
6. The controller of claim 1 , wherein retrieving information associated with the stylus from the generated signal-timing waveform comprises:
analyzing the generated signal-timing waveform to determine a frequency component of the generated signal-timing waveform; and
determining, from the determined frequency component of the generated signal-timing waveform, the information associated with the stylus.
7. The controller of claim 1 , wherein the electrode of the touch sensor comprises a drive electrode reconfigured to sense signals.
8. A method comprising:
initiating an acquisition of a first signal from an electrode of a touch sensor according to an acquisition frequency of the touch sensor, wherein the first signal is associated with a first transmission from a stylus;
storing a first modulated signal, wherein the first modulated signal comprises a modulated form of the first signal;
initiating an acquisition of a second signal from the electrode of the touch sensor according to the acquisition frequency of the touch sensor, wherein the second signal is associated with a second transmission from the stylus;
reversing, with a controller, a polarity of the second signal, received in response to initiating the acquisition of the second signal from the electrode of the touch sensor according to the acquisition frequency of the touch sensor, to produce a third signal;
storing a second modulated signal, wherein the second modulated signal comprises a modulated form of the third signal;
generating a signal-timing waveform based on the first and second modulated signals; and
retrieving, with the controller, from the generated signal-timing waveform, information associated with the stylus.
9. The method of claim 8 , wherein:
the first modulated signal is stored at an end of the acquisition of the first signal;
the first signal is modulated by one or more third-party signals during the acquisition of the first signal;
the second modulated signal is stored at an end of the acquisition of the second signal;
the third signal is modulated by the one or more third-party signals during the acquisition of the second signal;
the signal-timing waveform is generated based on subtracting the second modulated signal from the first modulated signal;
the generated signal-timing waveform substantially suppresses the one or more third-party signals; and
the generated signal-timing waveform is based on the first and second signals.
10. The method of claim 8 , wherein the stylus is a passive stylus having a signal activator input.
11. The method of claim 10 , wherein the information associated with the passive stylus comprises a state of the signal activator input.
12. The method of claim 8 , wherein the information associated with the stylus comprises one or more of:
a proximity of the stylus from the touch sensor; and
a position of the stylus's projection onto the touch sensor.
13. The method of claim 8 , wherein retrieving information associated with the stylus from the generated signal-timing waveform comprises:
analyzing, with the controller, the generated signal-timing waveform to determine a frequency component of the generated signal-timing waveform; and
determining, with the controller, from the determined frequency component of the generated signal-timing waveform, the information associated with the stylus.
14. The method of claim 8 , wherein retrieving information associated with the stylus from the generated signal-timing waveform comprises:
determining, with the controller, a signal strength profile of the generated signal-timing waveform across a X axis and a Y axis of the touch sensor; and
determining, with the controller, from the determined signal strength profile of the generated signal-timing waveform, the information associated with the stylus.
15. The method of claim 8 , wherein the electrode of the touch sensor comprises a drive electrode reconfigured to sense signals.
16. A system comprising:
a stylus configured to transmit a stylus signal;
a touch sensor configured to receive the stylus signal from the stylus, the touch sensor comprising an electrode; and
a controller comprising one or more computer-readable non-transitory storage media embodying logic that is operable when executed to:
initiate an acquisition of a first stylus signal from the electrode of the touch sensor according to an acquisition frequency of the touch sensor, wherein the first stylus signal is associated with a first transmission from the stylus;
store a first modulated signal, wherein the first modulated signal comprises a modulated form of the first stylus signal;
initiate an acquisition of a second stylus signal from the electrode of the touch sensor according to the acquisition frequency of the touch sensor, wherein the second stylus signal is associated with a second transmission from the stylus;
reverse a polarity of the second stylus signal to produce a third signal;
store a second modulated signal, wherein the second modulated signal comprises a modulated form of the third signal;
generate a signal-timing waveform based on:
adding the first modulated signal and the second modulated signal; or
calculating a difference between the first modulated signal and the second modulated signal; and
retrieve, from the generated signal-timing waveform, information associated with the stylus.
17. The system of claim 16 , wherein the stylus comprises:
an electrically conductive stylus tip;
a signal generator coupled to the stylus tip; and
a signal activator input configured to initiate:
a coupling, in response to an actuation of the signal activator input, of a power source to the signal generator to thereby cause the signal generator to generate the stylus signal;
an application of the stylus signal to the stylus tip to thereby cause the stylus signal to be emitted by the stylus tip such that the emitted stylus signal is detectable by the touch sensor; and
a decoupling, in response to an end of the actuation, of the power source from the signal generator to thereby disable generation of the stylus signal by the signal generator.
18. The system of claim 17 , wherein:
the stylus further comprises a timer; and
the signal activator input is further configured to initiate a coupling, in response to the actuation of the signal activator input, of the power source to the timer to thereby activate the timer, wherein:
the signal generator generates the stylus signal if the activated timer has not expired; and
the generation of the stylus signal by the signal generator is disabled if the activated timer expires prior to the end of the actuation.
19. The system of claim 17 , wherein the signal activator input comprises one or more of:
a mechanical element located on an exterior surface of the stylus; and
a touch sensitive surface located on the exterior surface of the stylus.
20. The system of claim 17 , wherein the signal activator input comprises a mechanical element located on an exterior surface of the stylus, the mechanical element comprising one or more of:
a mechanical button;
a mechanical switch; and
a mechanical slider.
21. The system of claim 17 , wherein the signal generator comprises an oscillator.
22. The system of claim 17 , wherein:
a GND of the signal generator is coupled to a barrel of the stylus, wherein the barrel is electrically conductive; and
the coupling of the GND of the signal generator to the barrel of the stylus allows the GND of the signal generator to be electrically coupled to a user of the stylus.
23. The system of claim 17 , wherein a capacitive load of the stylus tip of the stylus is above a pre-determined threshold when the signal activator input is not actuated.
24. The system of claim 16 , wherein the stylus signal is a sinusoidal signal having:
a voltage amplitude of approximately 20V to approximately 30V; and
a frequency of approximately 14 kHz to approximately 16 kHz.