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.

FIELD

This relates generally to touch sensitive devices and, more specifically, to styluses for use with touch sensitive devices.

BACKGROUND

Touch sensitive devices have become popular as input devices to computing systems due to their ease and versatility of operation as well as their declining price. A touch sensitive device can include a touch sensor panel, which can be a clear panel with a touch sensitive surface, and a display device, such as a liquid crystal display (LCD), that can be positioned partially or fully behind the panel or integrated with the panel so that the touch sensitive surface can cover at least a portion of the viewable area of the display device. The touch sensitive device can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location often dictated by a user interface (UI) being displayed by the display device. In general, the touch sensitive device can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event.

As touch sensing technology continues to improve, touch sensitive devices are increasingly being used to compose and mark-up electronic documents. In particular, styluses have become popular input devices as they emulate the feel of traditional writing instruments. However, while touch sensing technology has greatly improved over the past few years, little has been done to improve the stylus itself. Most conventional styluses simply include a bulky tip made of a material capable of interacting with the touch sensitive device. As a result, conventional styluses lack the precision and control of traditional writing instruments.

SUMMARY

Styluses capable of receiving stimulation and force signals and 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.

In one example, a touch sensor of a touch sensitive device 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 that a stylus has been detected, a location of the stylus on the touch sensor, and an amount of pressure applied by the stylus to the touch sensitive device. The determinations can be made based on properties of the touch signal caused by the stylus stimulation signal.

Processes for generating and processing stylus stimulation signals are also disclosed.

DETAILED DESCRIPTION

In the following description of example embodiments, reference is made to the accompanying drawings in which it is shown by way of illustration specific embodiments that can be practiced. It is to be understood that other embodiments can be used and structural changes can be made without departing from the scope of the various embodiments.

This relates to styluses capable of receiving stimulation and force signals and generating stylus stimulation signals and touch sensitive devices capable of receiving stylus stimulation signals. 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. A touch sensor of a touch sensitive device 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 that a stylus has been detected, a location of the stylus on the touch sensor, and an amount of pressure applied by the stylus to the touch sensitive device. The determinations can be made based on properties of the touch signal caused by the stylus stimulation signal. Processes for generating and processing stylus stimulation signals are also disclosed.

FIG. 1illustrates touch sensor100that can be used to detect touch events on a touch sensitive device, such as a mobile phone, tablet, touchpad, portable computer, portable media player, or the like. Touch sensor100can include an array of touch regions or nodes105that can be formed at the crossing points between rows of drive lines101(D0-D3) and columns of sense lines103(S0-S4). Each touch region105can have an associated mutual capacitance Csig111formed between the crossing drive lines101and sense lines103when the drive lines are stimulated. The drive lines101can be stimulated by stimulation signals107provided by drive circuitry (not shown) and can include an alternating current (AC) waveform. The sense lines103can transmit touch signals109indicative of a touch at the touch sensor100to sense circuitry (not shown), which can include a sense amplifier for each sense line, or a fewer number of sense amplifiers that can be multiplexed to connect to a larger number of sense lines.

To sense a touch at the touch sensor100, drive lines101can be stimulated by the stimulation signals107to capacitively couple with the crossing sense lines103, thereby forming a capacitive path for coupling charge from the drive lines101to the sense lines103. The crossing sense lines103can output touch signals109, representing the coupled charge or current. When an object, such as a stylus, finger, etc., touches the touch sensor100, the object can cause the capacitance Csig111to reduce by an amount ΔCsig at the touch location. This capacitance change ΔCsig can be caused by charge or current from the stimulated drive line101being shunted through the touching object to ground rather than being coupled to the crossing sense line103at the touch location. The touch signals109representative of the capacitance change ΔCsig can be transmitted by the sense lines103to the sense circuitry for processing. The touch signals109can indicate the touch region where the touch occurred and the amount of touch that occurred at that touch region location.

While the embodiment shown inFIG. 1includes four drive lines101and five sense lines103, it should be appreciated that touch sensor100can include any number of drive lines101and any number of sense lines103to form the desired number and pattern of touch regions105. Additionally, while the drive lines101and sense lines103are shown inFIG. 1in a crossing configuration, it should be appreciated that other configurations are also possible to form the desired touch region pattern. WhileFIG. 1illustrates mutual capacitance touch sensing, other touch sensing technologies may also be used in conjunction with embodiments of the disclosure, such as self-capacitance touch sensing, resistive touch sensing, projection scan touch sensing, and the like. Furthermore, while various embodiments describe a sensed touch, it should be appreciated that the touch sensor100can also sense a hovering object and generate hover signals therefrom.

FIG. 2illustrates a block diagram of an exemplary stylus200that can be used with a touch sensitive device, such as a mobile phone, touchpad, portable computer, or the like. Stylus200can generally include tip201, ring203, body207, and stylus stimulation signal circuitry205located within body207. As will be described in greater detail below, stylus stimulation signal circuitry205can be used to generate a stimulation signal that can be transmitted to a touch sensitive device through tip201. Tip201can include a material capable of transmitting the stylus stimulation signal from stylus stimulation signal circuitry205to the touch sensitive device, such as a flexible conductor, a metal, a conductor wrapped by a non-conductor, a non-conductor coated with a metal, a transparent conducting material (e.g., indium tin oxide (ITO)) or a transparent non-conductive material (e.g., glass) coated with a transparent (e.g., ITO) (if the tip is also used for projection purposes) or opaque material, or the like. In some examples, tip201can have a diameter of 1 mm or less. Tip201can be coupled to body207by ring203. Ring203can include a conductive material, such as a flexible conductor, a metal, a conductor wrapped by a non-conductor, a non-conductor coated with a metal, a transparent conducting material (e.g., ITO) or a transparent non-conductive material (e.g., glass) coated with a transparent (e.g., ITO if the tip is used for projection purposes) or opaque material, or the like. Ring203can serve other purposes, such as providing an alternative means for transmitting the stylus stimulation signal from the stylus to the touch sensitive device by serving as an antenna for a wireless module (e.g., RFID, Bluetooth, WI-FI, or the like). Similarly, tip201can also be used to sense the touch signal from the touch sensitive device. Both tip201and ring203can be segmented and each segment can be independently controlled according to the description above.

In some examples, stylus200can be a modular stylus, such as that described in U.S. patent application Ser. No. 13/560,960, entitled “Modular Stylus Device”.

FIG. 3illustrates a functional block diagram of an exemplary system300showing the interaction between stylus301, touch sensor321, and touch circuitry341. In this embodiment, a stimulation signal from touch sensor321can be detected at a location where the tip of stylus301contacts or is near touch sensor321(e.g., where the tip contacts or hovers above a screen of a touch sensitive device). A modified stimulation signal can then be transmitted back into touch sensor321at the same frequency in phase or at an arbitrary phase (including quadrature) at the same location. The modified stimulation signal can be transmitted back into touch sensor321through the tip and/or ring of stylus301. It should be appreciated thatFIG. 3is a functional block diagram and that the actual components used to implement the various portions of system300can vary and one of ordinary skill, given the functional diagram, can select known circuit elements to implement the system.

Stylus301is one example of stylus200that can be used as an input device to a touch sensitive device having a touch sensor similar or identical to touch sensor100. Stylus301can be configured to generate a stylus stimulation signal having a greater magnitude than that generated by the touch sensitive device. Thus, when stylus301is used with a touch sensitive device, stylus301can cause the touch sensitive device to measure a “negative” touch. In other words, the charge detected at the stylus' touch location can be greater than the amount of charge detected when no touch is present. This is different than non-stylus touch events, which typically cause the charge detected at the touch location to decrease.

Stylus301can include amplifier305coupled to receive a stimulation signal (e.g., a stimulation signal similar or identical to stimulation signal107) generated by an associated touch sensitive device and transmit a stylus stimulation signal to the associated touch sensitive device. The associated touch sensitive device can include a touch sensitive device in contact with, or in close proximity to, the tip of stylus301. Stylus301can receive the stimulation signal through the touch sensor (e.g., touch sensor321) of the touch sensitive device. Amplifier305can be configured to receive and amplify the stimulation signal by an amount based at least in part on a force detected by force sensor309and a gain vector generated by processor307. In some examples, amplifier305can be configured to amplify the received stimulation signal by an amount representing an increase of capacitance by 0.1 pF or more, depending on the particular configuration. However, it should be appreciated that other amplifications can be used depending on the system design.

Stylus301can further include force sensor309to detect an amount of force applied to the tip of stylus301. Force sensor309can include any type of force sensor, such as a capacitive pressure sensor, semiconductor strain gauge, or the like. The amount of force detected by force sensor309can be used by amplifier305to determine the amount of amplification to be applied to the stimulation signal received from the associated touch sensitive device. In this way, the magnitude of the amplified stimulation signal generated by amplifier305can be adjusted based on how hard the stylus tip is applied to the surface of the associated touch sensitive device. This allows stylus301to convey information associated with the location of its tip on the surface of the touch sensitive device as well as the amount of force being applied to the surface of the touch sensitive device. In response, the touch sensitive device can interpret the location and force information as two different inputs. For example, in a drawing application, a brush stroke can be displayed on the screen of the touch sensitive device corresponding to a location of the tip of stylus301and with a width corresponding to the amount of force being applied to the touch sensitive device by the tip of stylus301.

Stylus301can further include processor307coupled to receive an amplified stimulation signal from amplifier305. Processor307can be configured to generate a signal representative of a gain vector that can be used to modulate the amplified output of amplifier305. The processor can monitor the stimulation signal received from the touch sensor321in order to synchronize the gain vector with the received stimulation sequence. The gain vector signal can be transmitted to mixer306where it, along with the output of force sensor309, can be used to control the amount of amplification applied to the stimulation signal from touch sensor321. The amplified and modulated stimulation signal can be transmitted back into touch sensor321as the stylus stimulation signal.

It should be appreciated that amplifier305can be configured to amplify the received stimulation signal based on the amount of force detected by force sensor309and the gain vector of processor307in many ways. In one example, amplifier305can include a regenerative amplifier operable to amplify the received stimulation signal using a feedback loop between the amplifier output and the amplifier input.FIG. 14illustrates a symbolic illustration of one or more capacitive elements1401coupled between the input and output of an amplifier305. The received stimulation signal can be added at the amplifier input in phase. The amplified stimulation signal can be transmitted to touch sensor321, thereby increasing the signal charge locally between drive and sense (negative pixel) as opposed to reducing it in the presence of a touch. In this example, force sensor309can control one or more capacitive elements1401coupled between the input and output of amplifier305. Switches can also be coupled to the capacitive elements to selectively couple the capacitive elements between the input and output of amplifier305. The one or more capacitive elements1401can be configured such that the capacitance of each of the one or more capacitive elements is inversely related to the amount of force applied to the tip of stylus301. Thus, as the force against the tip of stylus300increases, the capacitance of the one or more capacitive elements1401of force sensor309decreases, thereby increasing the overall gain of amplifier305. Conversely, as the force against the tip of stylus300decreases, the capacitance of the one or more capacitive elements1401of force sensor309increases, thereby decreasing the overall gain of amplifier305. In this example, processor307can be configured to cause amplifier305to modulate the stimulation signal using a gain vector by selectively coupling one of the one or more capacitive elements1401(each having a different capacitance value) between the input and output of amplifier305based on the gain vector. Processor307can accomplish this by selectively opening and closing the switches coupled to each capacitive element. In this way, the gain caused by each of the capacitive elements1401can be changed by adjusting the pressure applied to the tip of stylus301while processor307can modulate the amplified signal by selecting between each of the capacitive elements having different capacitance values.

In some examples, amplifier305can be configured to yield a loop gain of less than one to prevent oscillation. In other alternative examples, amplifier305can include a super regenerative amplifier, comprised of an amplifier with a loop gain of greater than 1 and a quench signal generator having a quench rate based on the received stimulation signal from touch sensor321. In these examples, the quench signal generator can apply a quench signal that can cause the gain of the regenerative amplifier to drop substantially below the gain needed for the regenerative amplifier to sustain oscillation, causing the regenerative amplifier to repeatedly go into oscillation at the beginning of each scan step. In yet other examples, amplifier305can add the received stimulation signal at the amplifier input in a different phase (including quadrature).

System300can further include touch sensor321of a touch sensitive device. Touch sensor321can include a touch sensor similar or identical to touch sensor100, described above. As shown inFIG. 3, touch sensor321can include a drive line329coupled to receive a stimulation signal similar or identical to stimulation signal107from touch circuitry341and a sense line331capacitively coupled to drive line329and coupled to transmit a touch signal similar or identical to touch signal109to touch circuitry341. It should be appreciated that touch sensor321is shown with only one drive line and one sense line for illustrative purposes only and that touch sensor321can actually include any number of drive lines and any number of sense lines.

A mutual capacitance Csig327can be formed between the crossing drive line329and sense line331when the drive line is stimulated. Similarly, a mutual capacitance Cts323and Ctd325can be formed between the tip of stylus301and sense line331and drive line329, respectively, when the stylus stimulation signal is generated. As mentioned above, if the tip of stylus301is placed near or at the crossing point between drive line329and sense line331, stylus301can receive the stimulation signal transmitted on drive line329via the capacitive path formed between the stylus tip and drive line329, amplify the received stimulation signal using amplifier305, force sensor309, and processor307, and transmit an amplified stimulation signal in the form of a stylus stimulation signal back into touch sensor321via the capacitive path formed between the stylus tip and sense line331. Thus, the touch signal generated by sense line331can include charges coupled from both drive line329and stylus301. As a result, the amount of charge detected by sense line331can increase when the tip of stylus301is placed on or above the crossing point between drive line329and sense line331. This increase in charge can be used by the touch sensitive device to distinguish a stylus touch event from a non-stylus touch event because, as mentioned above, non-stylus touch events typically cause capacitance Csig327to decrease due to charge or current from the stimulated drive line329being shunted through the non-stylus object to ground rather than being coupled to the crossing sense line331at the touch location. Moreover, the touch sensitive device can determine the location of the stylus touch event because the same stimulation signal being driven on drive line329is being amplified and transmitted back into the touch sensor at the crossing point between drive line329and sense line331.

System300can further include touch circuitry341included in or associated with the touch sensitive device. Touch circuitry341can include multi-stim matrix343stored in a computer-readable storage medium. Multi-stim matrix343can include a matrix containing stimulation phase information for stimulation signals that can be simultaneously applied to the drive lines of touch sensor321, such as that described in U.S. patent Ser. No. 12/208,329, entitled “Multiple Stimulation Phase Determination.” Specifically, each row of the matrix can represent a single step among multiple steps needed to compute values for generating an image of touch, each column of the matrix can represent a drive line of touch sensor panel321to be stimulated, and each cell of the matrix can represent the phase of a stimulation signal to be applied to a particular drive line in a particular step. In one example, multi-stim matrix343can include an additional row and column to support the stylus stimulation signal from stylus301. Specifically, the additional column can represent a drive line that is not driven, or a drive line that does not actually exist on touch sensor panel321. The purpose of the additional column is to detect the stylus stimulation signal. Touch circuitry341can further include inverse multi-stim matrix353stored in a computer-readable storage medium. Inverse multi-stim matrix353can include a matrix representing an inverse of multi-stim matrix343for decoding a touch signal received from a sense line of touch sensor321to generate a touch image representing a touch detected by touch sensor321. These matrices will be described in greater detail below with respect toFIGS. 4-7.

Referring back toFIG. 3, touch circuitry341can further include transmitter channel345coupled to transmit a stimulation signal to drive line329of touch sensor321. Transmitter channel345can be configured to generate a stimulation signal similar or identical to stimulation signal107to be applied to drive line329based on the phase information contained in multi-stim matrix343. In some examples, the stimulation signal can have a frequency between 80-120 KHz (e.g., 90, 100, or 110 KHz) and an amplitude between 3-5V (e.g., 4V). In other examples, the stimulation signal can have a frequency between 100 KHz to 1 MHz or higher (e.g., between 100-300 KHz or 100-500 KHz). Although not shown, touch circuitry341can include one transmitter channel for each drive line of touch sensor321.

Touch circuitry341can further include receiver circuitry347coupled to receive a touch signal from sense line331of touch sensor321. Receiver circuitry347can include amplifiers, filters, and/or analog to digital converters that one of ordinary skill in the art can select to appropriately process the touch signal received from sense line331. Although not shown, touch circuitry341can include additional receiver circuitry for each sense line of touch sensor321.

Touch circuitry341can further include in-phase (I-phase) demodulation circuitry349configured to demodulate the touch signal received from receiver circuitry347. I-phase demodulation circuitry347can include a demodulation mixer and a demodulation integrator to extract the I-phase component of the touch signal output by sense line331. Although not shown, touch circuitry341can include additional I-phase demodulation circuitry for each sense line of touch sensor321. In some examples, transmitter channel345, receiver circuitry347, and I-phase demodulation circuitry349can include circuitry similar or identical to that described in U.S. patent application Ser. No. 11/818,345, which is incorporated by reference herein in its entirety as if put forth in full below.

Touch circuitry341can further include multi-stim decode circuitry351configured to decode the I-phase component of the touch signal received from I-phase demodulation circuitry341. Multi-stim decode circuitry351can include a mixer coupled to multiply the I-phase component of the touch signal received from I-phase demodulation circuitry341with inverse multi-stim matrix353. Multi-stim decode circuitry351can further include an integrator coupled to receive the output of the mixer and to output touch image355representing a touch detected by sense line331of touch sensor321. Although not shown, touch circuitry341can include additional multi-stim decode circuitry for each sense line of touch sensor3211.

FIG. 4illustrates a functional block diagram of another exemplary system400showing the interaction between stylus401, touch sensor421, and touch circuitry441. In this embodiment, similar to that shown inFIG. 3, stylus401can receive a stimulation signal from touch sensor421at a location where the tip of stylus401contacts or is near touch sensor421(e.g., where the tip contacts or hovers above a screen of a touch sensitive device). A modified stimulation signal can then be transmitted back into touch sensor421at the same frequency in phase or at an arbitrary phase (including quadrature) at the same location. The modified stimulation signal can be transmitted back into touch sensor421through the tip and/or ring of stylus401. It should be appreciated thatFIG. 4is a functional block diagram and that the actual components used to implement the various portions of system400can vary and one of ordinary skill, given the functional diagram, can select known circuit elements to implement the system.

System400can include stylus401, amplifier405, processor407, mixer406, force sensor409, touch sensor421, Cts423, Ctd425, Csig427, drive line429, sense line431, multi-stim matrix443, transmitter channel445, receiver circuitry447, and inverse matrix453similar or identical to stylus301, amplifier305, processor307, mixer306, force sensor309, touch sensor321, Cts323, Ctd325, Csig327, drive line329, sense line331, multi-stim matrix343, transmitter channel345, receiver circuitry347, and inverse matrix353, respectively. However, touch circuitry441can include two demodulation paths. The first demodulation path can include stylus demodulation circuitry449and multi-stim decode circuitry451for demodulating the touch signal received from receiver circuitry447at a first touch phase to generate stylus image456. The second demodulation path can include touch demodulation circuitry457and multi-stim decode circuitry459for demodulating the touch signal received from receiver circuitry447at a second stylus phase to generate touch image455, Including a phase shift between the touch and stylus signals further helps to distinguish the touch and stylus signals in addition to the latter having a positive phase. In some examples, the difference between the first and second phases can be 90 degrees. In other examples, the phase difference between the first and second phases can have a different value.

FIG. 5illustrates an exemplary touch and stylus stimulus combo matrix that can be used in systems300or400. In this embodiment, a touch stimulus matrix may be extended by M columns and M rows to form the modified touch and stylus stimulus combo matrix. The first N columns may be used for touch stimulus and the M columns may be used for stylus magnitude. Each column vector can correspond to a different channel. In order for the stimulus matrix to be invertible, the matrix should be a square matrix and therefore can be extended by M rows.FIG. 6illustrates M exemplary stylus stimulus vectors. Each stylus stimulus vector represents a copy of one of the M column vectors from the touch and stylus stimulus combo matrix shown inFIG. 5. Using the touch and stylus stimulus combo matrix, the system can support a total of N styluses.

FIG. 7illustrates a simplified view of a touch/stylus combo system that utilizes separate channels to encode stylus magnitude. The touch and stylus stimulus combo matrix is extended by N columns and N rows, where N is the number of stylus or devices for which to encode magnitude information. In this example, the touch controller can drive the M drive lines for which touch and stylus location need to be resolved. M touch pixels can be modulated along the M touch pixels along a sense line by touch and up to N stylus devices. The N stylus devices may potentially modulate different touch pixels along a sense line. Each stylus device can have its own stylus stimulus vector, which represents a copy of one of the M column vectors from the touch and stylus stimulus combo matrix. The stylus can modulate the gain of the amplifier (e.g., amplifier305or405) as a function of the stylus stimulus vector or can add its own stimulus signal directly to a given touch pixel (e.g., through the stylus ring). The stimuli from the N styluses can be synchronized in the stylus device by the respective stylus device monitoring the stimulus signal at a given touch panel location and then synchronizing its own stimulus with the received stimulus signal at that touch panel location. For example, synchronization can occur at the first scan step, representing the first row vector in the touch and stylus stimulus combo matrix. In some embodiments, all elements in the first row vector may be 1 (i.e., all M stimulus signals can be driven in positive phase), if the touch and stylus stimulus combo matrix is a hadamard matrix. The stylus device can use this first step to synchronize its own stimulus. The composite signal at the sense line can be vector demodulated with a decode matrix, which represents the inverse of the touch and stylus stimulus combo matrix. The touch and stylus locations can be stored in the touch and stylus result vector, which is comprised of M entries containing M elements indicating the location/magnitude of touch and styluses and N dedicated stylus magnitudes.

In some examples, some or all of the functional blocks of touch circuitry341or441can be implemented by ASIC processor, ARM processor, other electrical components, or combinations thereof.

FIG. 8illustrates a functional block diagram of another exemplary system800showing the interaction between stylus801, touch sensor821, and touch circuitry841. It should be appreciated thatFIG. 8is a functional diagram and that the actual components used to implement the various portions of system800can vary and one of ordinary skill, given the functional diagram, can select known circuit elements to implement the system

Stylus801is one example of stylus200that can be used as an input device to a touch sensitive device having a touch sensor similar or identical to touch sensor100. Stylus801can be configured to generate a stylus stimulation signal having a frequency that is different than a frequency of a stimulation signal generated by the touch sensitive device. In some examples, the stylus stimulation frequency can be between 40-60 KHz (e.g., about 50 Khz) greater than or less than the frequency of a stimulation signal from a touch sensor. Thus, when stylus801is used with a touch sensitive device, stylus801can cause the touch sensitive device to generate a touch signal containing signals having two or more different frequencies.

Stylus801can optionally include sense amplifier805coupled to receive a stimulation signal (e.g., a stimulation signal similar or identical to stimulation signal107) generated by an associated touch sensitive device and transmit a stylus stimulation signal to the associated touch sensitive device. The associated touch sensitive device can include a touch sensitive device in contact with, or in close proximity to, the tip of stylus801. Sense amplifier805can be used to amplify the received stimulation signal to a level sufficient to be used by stylus801to generate a stylus stimulation signal, which is described in greater detail below. However, if the strength of the received stimulation signal is sufficiently high, sense amplifier805can be omitted from stylus801.

Stylus801can further include force sensor809for detecting the amount of force applied to the tip of stylus801. Force sensor809can be similar or identical to force sensor309, described above. For example, force sensor809can include any type of force sensor, such as a capacitive pressure sensor, semiconductor strain gauge, or the like, operable to detect the amount of force applied to the tip of stylus801. The amount of force detected by force sensor809can be used to modulate an oscillating signal generated by oscillator813. In this way, the magnitude of the oscillating signal generated by oscillator813can be adjusted based on how hard the stylus tip is applied to the surface of the associated touch sensitive device. As described above, this allows stylus801to convey information associated with the location of its tip on the surface of the touch sensitive device as well as the amount of force being applied to the surface of the touch sensitive device.

Stylus801can further include comparator811coupled to receive the output of force sensor809and a threshold voltage Vth. Comparator811can be configured to compare the output of force sensor809to the threshold voltage Vth and output a force detection signal based on the comparison. For example, the force detection signal can be driven high (or low, depending on the circuit design) when the output of force sensor809is greater than threshold voltage Vth and can be drive low (or high, depending on the circuit design) when the output of force sensor809is less than threshold voltage Vth.

Stylus801can further include processor803coupled to receive the force detection signal output by comparator811. Processor803can be configured to generate a power control signal based on the received force detection signal. For example, if the force detection signal is at a level indicating that the force detected by force sensor809is greater than a threshold amount (represented by threshold voltage Vth), processor803can drive the power control signal to a high level (or low, depending on the circuit design) to cause oscillator813to generate a signal. The force detection signal and the power control signal can be used to control the power state of some or all components within stylus801to improve battery life. For example, if the force is below the set force threshold, the device can be in an idle state and the device can remain in a low power state, thereby conserving battery power. When the force is above the force detection threshold, the device can transitions into an active mode. This way battery power can be conserved when the stylus is not actively being used.

Stylus801can further include oscillator813configured to generate an oscillating signal having frequency Foff. Oscillator813can include any type of oscillator, such as a tuned LC oscillator (e.g, a colpitts-oscillator), crystal oscillator, MEMS based oscillator, voltage controlled oscillator, RC oscillator, ring oscillator, or the like. In one example, oscillator813can be configured to generate a sinusoidal signal having an amplitude between 8-12V (e.g., 9, 10, or 11V) and a frequency Foffbetween 80-120 KHz (e.g., 90, 100, or 110 KHz). In other examples, the stimulation signal can have a frequency between 100 KHz to 1 MHz or higher (e.g., between 100-300 KHz or 100-500 KHz). The signal generated by oscillator813can have the same phase as the stimulation signal received from touch sensor821.

Stylus801can further include mixer807coupled to receive the output of force sensor809, the signal having frequency Foffoutput by oscillator813, and the amplified stimulation signal from sense amplifier805. Mixer807can be configured to modulate the amplitude of the signal having frequency Foffoutput by oscillator813by an amount corresponding to the force detected by force sensor809to generate a modulated oscillating signal. Mixer807can be further configured to mix the modulated oscillating signal with the amplified signal received from sense amplifier805to generate a stylus stimulation signal. The resultant composite stimulation signal can have a frequency equal to the frequency of the stimulation signal received from touch sensor821plus or minus the offset frequency Foffamplitude modulated by the force signal.

Stylus801can further include transmission amplifier815coupled to receive the stylus stimulation signal output by mixer807. Amplifier815can be configured to amplify the composite stimulation signal by an amount sufficient to be received by touch sensor821.

System800can further include touch sensor821of a touch sensitive device. Touch sensor821can include a touch sensor similar or identical to touch sensor100, described above. As shown inFIG. 8, touch sensor821can include a drive line829coupled to receive a stimulation signal similar or identical to stimulation signal107from touch circuitry841and a sense line831capacitively coupled to drive line829and coupled to transmit a touch signal similar or identical to touch signal109to touch circuitry841. It should be appreciated that touch sensor821is shown with only one drive line and one sense line for illustrative purposes only and that touch sensor821can actually include any number of drive lines and any number of sense lines.

A mutual capacitance Csig827can be formed between the crossing drive line829and sense line831when the drive line is stimulated. Similarly, a mutual capacitance Cts823and Ctd825can be formed between the tip of stylus801and sense line831and drive line829, respectively, when the stylus stimulation signal is generated. A mutual capacitance Crs833and Crd835can also be formed between the ring of stylus801and sense line831and drive line829, respectively, when the composite stylus stimulation signal is generated. As mentioned above, if the tip of stylus801is placed at the crossing point between drive line829and sense line831, stylus801can receive the stimulation signal transmitted on drive line829via the capacitive path formed between the stylus tip and drive line829, amplify the received stimulation signal using sense amplifier805, mix the amplified stimulation signal with a modulated oscillating signal generated by modulating a signal having frequency Foffby an amount corresponding to a force detected by force sensor809, and transmit the stylus stimulation signal back into touch sensor821via the capacitive path formed between the stylus ring and sense line831. Thus, the touch signal generated by sense line831can include charge coupled from both drive line829and stylus801.

System800can further include touch circuitry841included in or associated with the touch sensitive device. Touch circuitry841can be similar to touch circuitry341, described above, except that touch demodulation circuitry849and multi-stim decode circuitry851can be configured to demodulate the touch component of the signal output by receiver circuitry847and post the result in a touch image memory855. Touch circuitry841can further include stylus demodulation circuitry857and multi-stim decode circuitry859to demodulate the stylus component of the signal output by receiver circuitry847and post the result to stylus image memory861. In the illustrated example, stylus demodulation can occur at FSTM+/−FOFF, since the received signal on the stylus device can be FSTM and modulated with FOFF to generate the stylus signal. The touch demodulation can be performed at FSTM. Multi-stim matrix843, transmitter channel845, receiver circuitry847, and inverse matrix853can be similar or identical to multi-stim matrix343, transmitter channel345, receiver circuitry347, and inverse matrix353of touch circuitry341, respectively. However, multi-stim matrix843and inverse matrix853may not include an extra row and step like that contained in multi-stim matrix343and inverse matrix353. The differences between touch circuitry341and touch circuitry841will now be described in more detail.

Touch circuitry841can include separate demodulation and decode circuitry for handling stylus touch events and non-stylus touch events. Specifically, touch circuitry841can include touch demodulation circuitry849and multi-stim decode circuitry851to process non-stylus touch events and can include stylus demodulation circuitry857and multi-stim decode circuitry859to process stylus touch events.

Touch demodulation circuitry849can be configured to demodulate the portion of the touch signal received from receiver circuitry847having a frequency corresponding to the frequency of the stimulation signal generated by transmitter channel845. Touch demodulation circuitry849can include a demodulation mixer and a demodulation integrator to extract the touch component of the signal output by sense line831having the frequency corresponding to the frequency of the stimulation signal generated by transmitter channel845.

Multi-stim decode circuitry851can be configured to decode the touch component of the signal received from touch demodulation circuitry849. Multi-stim decode circuitry851can include a mixer coupled to multiply the touch component of the signal received from touch demodulation circuitry849with inverse multi-stim matrix853. Multi-stim decode circuitry851can further include an integrator coupled to receive the output of the mixer and to post the result in a touch image memory855, representing a non-stylus touch detected by sense line831of touch sensor821.

Stylus demodulation circuitry857can be configured to demodulate the portion of the touch signal received from receiver circuitry847having a frequency corresponding to the frequency of the stimulation signal generated by transmitter channel845plus or minus the offset frequency Foff. Stylus demodulation circuitry857can include a demodulation mixer and a demodulation integrator to extract the stylus component of the signal output by sense line831having the frequency corresponding to the frequency of the stimulation signal generated by transmitter channel845plus or minus the offset frequency Foff.

Multi-stim decode circuitry859can be configured to decode the stylus component of the signal received from stylus demodulation circuitry857. Multi-stim decode circuitry859can include a mixer coupled to multiply the stylus component of the touch signal received from stylus demodulation circuitry857with inverse multi-stim matrix853. Multi-stim decode circuitry859can further include an integrator coupled to receive the output of the mixer and to post the result in a touch image memory861, representing a stylus touch detected by sense line831of touch sensor821.

In some examples, the functional blocks of touch circuitry841can be implemented by ASIC processor, ARM processor, other electrical components, or combinations thereof.

While system800is shown and described above as using one signal having an offset frequency Foff, it should be appreciated that any number of these signals can be used. For example, stylus801can include any number of additional oscillators to generate additional signals to be modulated by an amount corresponding to the force detected by force sensor809. These additional signals can have varying frequencies and can each be mixed with the amplified stimulation signal received from sense amplifier805(or non-amplified stimulation signal received from touch sensor821if no sense amplifier805is used) to generate the stylus stimulation signal. In this example, touch circuitry841can also include additional circuitry to process the additional signals generated by stylus801. For example, touch circuitry can include additional I-phase demodulations circuits and multi-stim decoder circuits for each additional signal to be demodulated.

FIG. 9illustrates an exemplary process900for generating and transmitting a stylus stimulation signal. At block901, a stimulation signal can be received by a stylus from a touch sensitive device. The stimulation signal can be received by capacitively coupling a portion of the stylus to the touch sensitive device. In one example, a stimulation signal similar or identical to stimulation signal107can be generated by a touch sensitive device similar or identical to those shown inFIGS. 3,4, and8. The stimulation signal can be generated by a transmitter channel similar or identical to transmitter channels345,445, or845using a multi-stim matrix similar or identical to multi-stim matrix343,443, or843. The stimulation signal can be sent through a drive line similar or identical to drive lines329,429, or829of a touch sensor similar or identical to touch sensors321,421, or821. A stylus similar or identical to stylus200,301,401, or801having a tip similar or identical to tip201can receive the stimulation signal via a capacitive path formed between the drive line and the tip of the stylus when the stylus tip is placed on or near the touch sensitive surface of the touch sensitive device.

At block903, a stylus stimulation signal can be generated by changing a characteristic of the received stimulation signal. For example, one or more of a frequency or amplitude of the received stimulation signal can be changed to generate the stylus stimulation signal.

In one example, an amplifier similar or identical to amplifier305or405including a regenerative amplifier can be used to amplify the received stimulation signal. The amplification can be based on an amount of force detected by a force sensor similar or identical to force sensor309or409and a gain vector generated by processor similar or identical to processor307or407. The force sensor can detect the amount of force being applied to the tip of the stylus. In this way, the magnitude of the stylus stimulation signal can be varied by adjusting the amount of force being applied between the stylus tip and the surface of the touch sensitive device.

In another example, an oscillator and mixer similar or identical to oscillator813and mixer807can be used to change a frequency of the received stimulation signal. In this example, the oscillator can be configured to generate an oscillating signal (e.g., a sinusoidal signal) having a frequency that is different from that of the received stimulation signal. In some examples, the oscillator can be configured to turn on in response to a sufficient force being applied to the tip of the stylus as detected by a force sensor similar or identical to force sensor809. The stylus signal generated by the oscillator can modulated at a mixer similar or identical to mixer807by an output of the force sensor such that the amplitude of the amplitude modulated stylus stimulation signal corresponds to an amount of force detected by the force sensor. The amplitude modulated oscillating signal can be mixed with the received stimulation signal by a mixer similar or identical to mixer807to generate a stylus stimulation signal. In some examples, prior to mixing with the amplitude modulated stylus stimulation signal, the received stimulation signal can be amplified using an amplifier to increase the signal strength to a desirable amount. For example, an amplifier similar or identical to sense amplifier805can be used to amplify the received stimulation signal.

At block905, the stylus stimulation signal can be transmitted to the touch sensitive device. For example, the stylus stimulation signal generated at block903can be transmitted to the touch sensitive device via a capacitive path formed between the stylus device and the touch sensor of the device.

In one example, an amplitude-modulated stylus stimulation signal generated by a stylus similar or identical to stylus301or401can be transmitted to a touch sensor similar or identical to touch sensor321or421of a touch sensitive device via a capacitive path formed between the stylus device and the touch sensor of the device.

In another example, a frequency-shifted composite stylus stimulation signal generated by a stylus similar or identical to stylus801can be transmitted to a touch sensor similar or identical to touch sensor821of a touch sensitive device via a capacitive path formed between the stylus device and the touch sensor of the device. The frequency-shifted composite stylus stimulation signal can be amplified prior to transmission using a transmission amplifier similar or identical to transmission amplifier815.

FIG. 10illustrates an exemplary process1000for receiving and processing a touch signal having a stylus stimulation signal. At block1001, a stimulation signal can be generated by a touch sensitive device. The stimulation signal can be transmitted to drive lines of a touch sensor. In one example, a stimulation signal similar or identical to stimulation signal107can be generated by a touch sensitive device similar or identical to those shown inFIGS. 3,4, and8. The stimulation signal can be generated by a transmitter channel similar or identical to transmitter channels345,445, or845using a multi-stim matrix similar or identical to multi-stim matrices343,443, or843. The stimulation signal can be sent through a drive line similar or identical to drive lines329,429, or829of a touch sensor similar or identical to touch sensors321,421, or821.

At block1003, a touch signal having a stylus stimulation signal can be received by the touch sensitive device. The touch signal can represent a detected touch event on a touch sensitive surface of the touch sensitive device. In one example, a touch signal similar or identical to touch signal109can be received from a sense line similar or identical to sense line331,431, or831of a touch sensor similar or identical to touch sensor321,421, or821. The touch signal can contain a stylus stimulation signal generated by a stylus similar or identical to stylus301,401, or801. The stylus stimulation signal can be an amplitude-modulated and/or frequency-shifted version of the stimulation signal.

At block1005, the received sense signal can be processed. For example, the received sense signal can be filtered, converted from an analog to a digital signal, amplified, or combinations thereof. The signal can further be demodulated and decoded to generate a touch image representing a touch event detected by the touch sensor. In one example, a receiver circuitry similar or identical to receiver circuitry347,447, or847can be used to filter, convert the signal from an analog to a digital signal, amplify, or combinations thereof, the received sense signal.

In one example, the signal output by the receiver circuitry, such as receiver circuitry347, can be sent through demodulation circuitry similar or identical to demodulation circuitry349to extract the I-phase component of the touch signal. The demodulated signal can be transmitted to decode circuitry similar or identical to multi-stim decode circuitry351to generate a touch image similar or identical to touch image355. In another example, the signal output by the receiver circuitry, such as receiver circuitry447, can be sent through demodulation circuitry similar or identical to touch demodulation circuitry457and stylus demodulation circuitry449to extract the touch and stylus components of the touch signal. The demodulated signals can be transmitted to decode circuitry similar or identical to multi-stim decode circuitry451and459to generate a stylus image similar or identical to stylus image456and a touch image similar or identical to touch image455.

In another example, the signal output by receiver circuitry, such as receiver circuitry847, can be sent through two or more sets of demodulation circuitry similar or identical to touch and stylus demodulation circuitry849and857to extract the touch and stylus components of the touch signal. The touch demodulation circuitry849can be configured to demodulate the signal output by the receiver circuitry at a frequency corresponding to the frequency of the signal transmitted at block1001. The stylus demodulation circuitry857can be configured to demodulate the signal output by the receiver circuitry at the frequency corresponding to the frequency of the signal transmitted at block1001plus or minus an offset frequency corresponding to a frequency of an oscillating signal generated by the stylus device. If the stylus is configured to generate more than one oscillating signal, additional demodulation circuits can be used to demodulate the signal output by the receiver circuitry at frequencies corresponding to the frequency of the signal transmitted at block1001plus or minus offset frequencies corresponding to frequencies of the additional oscillating signals. The demodulated signal can be transmitted to decode circuitry similar or identical to multi-stim decode circuitry851or859. Additional decode circuitry can be included if additional demodulation circuits are used. The multi-stim decode circuitry can be used to generate touch images similar or identical to touch and stylus images855and861.

Using styluses301,401, and801or processes900or1000, a stylus device can be used to input both positional data and pressure into a touch sensitive device. These inputs can be used to improve a user experience in various applications. For example, in a drawing application, a user can use the stylus as a paintbrush, with the stylus' motion and pressure being detected by the touch sensitive device. As the user increases the pressure of the stylus against the touch sensitive device, the thickness of the brushstrokes can be increased. As the user reduces the pressure of the stylus against the touch sensitive device, the thickness of the brushstrokes can similarly decrease. In another example, when drawing with a line rather than a brush, the line thickness can change as a function of pressure. Similarly, when using the stylus as an eraser, the eraser width can vary as a function of pressure.

One or more of the functions relating to the generation or processing of a stylus stimulation signal described above can be performed by a system similar or identical to system1100shown inFIG. 11. System1100can include instructions stored in a non-transitory computer readable storage medium, such as memory1103or storage device1101, and executed by processor1105. The instructions can also be stored and/or transported within any non-transitory computer readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “non-transitory computer readable storage medium” can be any medium that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The non-transitory computer readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, a portable computer diskette (magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), an erasable programmable read-only memory (EPROM) (magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory such as compact flash cards, secured digital cards, USB memory devices, memory sticks, and the like.

The system1100shown inFIG. 11can be used in either the stylus to generate a stylus stimulation signal as described above with respect toFIGS. 3,4,8, and9, or the touch sensitive device to receive and process a touch signal as described above with respect toFIGS. 3,4,8, and10.

It is to be understood that the system is not limited to the components and configuration ofFIG. 11, but can include other or additional components in multiple configurations according to various embodiments. Additionally, the components of system1100can be included within a single device, or can be distributed between multiple devices.

FIG. 12illustrates an exemplary personal device1200, such as a tablet, that can be used with a stylus according to various embodiments.

FIG. 13illustrates another exemplary personal device1300, such as a mobile phone, that can be used with a stylus according to various embodiments.

Although embodiments have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the various embodiments as defined by the appended claims.