Low-power and low-frequency data transmission for stylus
In one embodiment, a method includes initiating an acquisition of a first signal from an electrode of a touch sensor according to an acquisition frequency of the touch sensor. The method also includes reversing, with a controller, a polarity of the first signal to produce a second signal. The method also includes storing a first modulated signal at an end of the acquisition of the first signal, where the first modulated signal includes the second signal as modulated by one or more third-party signals during the acquisition of the first signal.
1. 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 driven at least in part by one or more objects within proximity of the touch sensor;
reversing, with a controller, a polarity of the first signal to produce a second signal;
storing a first modulated signal at an end of the acquisition of the first signal, wherein the first modulated signal comprises the second signal as modulated by one or more third-party signals during the acquisition of the first signal;
initiating an acquisition of a third signal from the electrode of the touch sensor, wherein:
the acquisition of the third signal precedes the acquisition of the first signal according to the acquisition frequency of the touch sensor; and
the third signal is driven at least in part by the one or more objects within proximity of the touch sensor;
storing a second modulated signal at an end of the acquisition of the third signal, wherein the second modulated signal comprises the third signal as modulated by the one or more third-party signals during the acquisition of the third signal; and
subtracting the first modulated signal from the second modulated signal to:
substantially suppress the one or more third-party signals; and
indicate whether the one or more objects have come within proximity of the touch sensor.
2. The method of claim 1 , wherein each third-party signal is substantially equivalent to a sinusoid signal.
3. The method of claim 2 , wherein the acquisition frequency of the touch sensor is larger than a frequency of each third-party signal.
4. The method of claim 1 , further comprising:
adding the first and second modulated signals to:
substantially suppress the first and third signals; and
compose a signal timing waveform for the electrode of the touch sensor, the signal timing waveform being produced at least in part by the one or more third-party signals.
5. The method of claim 4 , wherein:
adding the first and second modulated signals if and only if one or more objects are detected to be within proximity of the touch sensor.
6. The method of claim 4 , wherein the one or more third-party signals are transmitted by a third-party device and received by the touch sensor, the third-party device comprising a physical controller.
7. The method of claim 6 , wherein the third-party device is a stylus and the physical controller is a button.
8. The method of claim 6 , further comprising:
processing the signal timing waveform to indicate whether the physical controller of the third-party device is activated.
9. A computer-readable non-transitory storage medium embodying logic that is configured 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, wherein the first signal is driven at least in part by one or more objects within proximity of the touch sensor;
reverse a polarity of the first signal to produce a second signal;
store a first modulated signal at an end of the acquisition of the first signal, wherein the first modulated signal comprises the second signal as modulated by one or more third-party signals during the acquisition of the first signal;
initiate an acquisition of a third signal from the electrode of the touch sensor, wherein:
the acquisition of the third signal precedes the acquisition of the first signal according to the acquisition frequency of the touch sensor; and
the third signal is driven at least in part by the one or more objects within proximity of the touch sensor;
store a second modulated signal at an end of the acquisition of the third signal, wherein the second modulated signal comprises the third signal as modulated by the one or more third-party signals during the acquisition of the third signal; and
subtract the first modulated signal from the second modulated signal to:
substantially suppress the one or more third-party signals; and
indicate whether the one or more objects have come within proximity of the touch sensor.
10. The medium of claim 9 , wherein each third-party signal is substantially equivalent to a sinusoid signal.
11. The medium of claim 10 , wherein the acquisition frequency of the touch sensor is larger than a frequency of each third-party signal.
12. The medium of claim 9 , wherein the logic is further configured when executed to:
add the first and second modulated signals to:
substantially suppress the first and third signals; and
compose a signal timing waveform for the electrode of the touch sensor, the signal timing waveform being produced at least in part by the one or more third-party signals.
13. The medium of claim 12 , wherein the one or more third-party signals are transmitted by a third-party device and received by the touch sensor, the third-party device comprising a physical controller.
14. The medium of claim 13 , wherein the third-party device is a stylus and the physical controller is a button.
15. A touch sensor system comprising:
a touch sensor;
a computer-readable non-transitory storage medium coupled to the touch sensor and embodying logic that is configured when executed to:
initiate an acquisition of a first signal from an electrode of the touch sensor according to an acquisition frequency of the touch sensor, wherein the first signal is driven at least in part by one or more objects within proximity of the touch sensor;
reverse a polarity of the first signal to produce a second signal;
store a first modulated signal at an end of the acquisition of the first signal, wherein the first modulated signal comprises the second signal as modulated by one or more third-party signals during the acquisition of the first signal;
initiate an acquisition of a third signal from the electrode of the touch sensor, wherein:
the acquisition of the third signal precedes the acquisition of the first signal according to the acquisition frequency of the touch sensor; and
the third signal is driven at least in part by the one or more objects within proximity of the touch sensor;
store a second modulated signal at an end of the acquisition of the third signal, wherein the second modulated signal comprises the third signal as modulated by the one or more third-party signals during the acquisition of the third signal; and
subtract the first modulated signal from the second modulated signal to:
substantially suppress the one or more third-party signals; and
indicate whether the one or more objects have come within proximity of the touch sensor.
16. The touch sensor system of claim 15 , further comprising an associated stylus, the associated stylus comprising:
a power source;
an oscillator, the oscillator being configured to generate a sinusoid signal, the sinusoid signal having a frequency that is lower than the acquisition frequency of the touch sensor;
a voltage converter, the voltage converter being configured to convert an output of the power source to an input power source for the oscillator;
a stylus tip, the stylus tip being configured to receive the sinusoid signal from the oscillator for transmission to the touch sensor; and
a button, the button being configured to start or stop the transmission of the sinusoid signal to the touch sensor via the stylus tip.