Stylus device
Styluses capable of generating stylus stimulation signals and touch sensitive devices capable of receiving stylus stimulation signals are disclosed. In one example, a stylus can receive a stimulation signal from a touch sensor of a touch sensitive device and generate a stylus stimulation signal by changing an amplitude or frequency of the received stimulation signal. The stylus can transmit the stylus stimulation signal back into the touch sensor of the touch sensitive device. The touch sensor can generate a touch signal based on the device's own stimulation signals and the stylus stimulation signal. The touch sensitive device can process the touch signal to determine a location of the stylus on the touch sensor. The stylus can include a force sensor to detect an amount of force applied to a tip of the stylus. The stylus stimulation signal can be modulated based on the force detected by the force sensor.
1. A stylus comprising:
a stylus tip capable of receiving a stimulation signal from a touch sensitive device and further capable of transmitting a stylus stimulation signal to the touch sensitive device;
a force sensor circuit capable of detecting a force applied to the stylus tip;
an amplification circuit coupled to receive the stimulation signal from the stylus tip, the amplification circuit comprising a processor and an amplifier, the processor coupled to receive an output signal from the amplifier and capable of generating a gain signal, wherein the amplification circuit is capable of modulating the received stimulation signal to generate the stylus stimulation signal based on the gain signal and the force detected by the force sensor circuit; and
a mixer circuit coupled to receive the gain signal and an output from the force sensor circuit and capable of controlling the amount of amplification applied to the received stimulation signal based on the output from the force sensor circuit and the gain signal.
2. The stylus of claim 1 , wherein a phase and a frequency of the stylus stimulation signal are at least substantially equal to a phase and a frequency of the stimulation signal from the touch sensitive device.
3. The stylus of claim 1 , wherein the amplification circuit comprises a regenerative or super regenerative amplifier, and wherein a quench rate of the super regenerative amplifier is synchronous to at least a portion of the received stimulation signal and a gain of the super regenerative amplifier is based on the received stimulation signal.
4. The stylus of claim 1 , wherein the amplification circuit further comprises a plurality of capacitive elements switchably coupled between an input and an output of the amplifier and the gain signal selectively couples one or more of the plurality of capacitive elements to modulate an amplitude of the received stimulation signal.
5. The stylus of claim 1 , wherein the amplification circuit further comprises a plurality of capacitive elements switchably coupled between an input and an output of the amplifier and the force sensor circuit is capable of adjusting the capacitance of one or more of the plurality of capacitive elements based on the amount of force applied to the stylus tip.
6. A method comprising:
receiving a stimulation signal from a touch-sensitive device;
generating a stylus stimulation signal based on the received stimulation signal and a force detected by a force sensor, wherein generating the stylus stimulation signal comprises
generating a gain vector using a processor receiving an amplified version of the received stimulation signal,
modulating an amplitude of the received stimulation signal based at least in part on the output of a mixer circuit, wherein the mixer is coupled to receive the gain vector and an output from the force sensor; and
transmitting the generated stylus stimulation signal to the touch-sensitive device.
7. The method of claim 6 , wherein generating the stylus stimulation signal further comprises selectively coupling one or more capacitive elements between the input and output of an amplifier based on the gain vector to modulate the amplitude of the received stimulation signal.
8. The method of claim 6 , wherein generating the stylus stimulation signal comprises modulating the amplitude of the received stimulation signal using a regenerative amplifier.