Method of waking up and a portable electronic device configured to perform the same

Methods of waking a portable electronic device are disclosed. In one embodiment, the method comprises: causing the portable electronic device to enter a sleep mode in which a touch-sensitive display is deactivated a force sensing transducer measures forces applied to the touch-sensitive display at a reduced rate relative to a rate of a full power mode when in the sleep mode; causing a force sensing transducer to measure forces applied to the touch-sensitive display at the rate of the full power mode in response to detection of an inertial event; causing the touch-sensitive display to be reactivated in response to detection of a force which is greater than a predetermined wake force threshold; and causing the portable electronic device to wake in response to detection of a touch event within a first predetermined duration of the detection of the force which is greater than a predetermined wake force threshold.

TECHNICAL FIELD

The present disclosure relates to portable electronic devices, including but not limited to portable electronic devices having touch screen displays and their control.

BACKGROUND

Electronic devices, including portable electronic devices, have gained widespread use and may provide a variety of functions including, for example, telephonic, electronic messaging and other personal information manager (PIM) application functions. Portable electronic devices include, for example, several types of mobile stations such as simple cellular telephones, smart telephones, wireless personal digital assistants (PDAs), and laptop computers with wireless 802.11 or Bluetooth™ capabilities.

Portable electronic devices such as PDAs or smart telephones are generally intended for handheld use and ease of portability. Smaller devices are generally desirable for portability. A touch-sensitive display, also known as a touchscreen display, is particularly useful on handheld devices, which are small and have limited space for user input and output. The information displayed on the touch-sensitive displays may be modified depending on the functions and operations being performed. The power consumed by touch-sensitive displays is a relatively large portion of the total power draw for the device. Accordingly, improvements which reduce the power consumption of touch-sensitive displays of portable electronic devices are desirable.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The present disclosure provides a wakeup detection circuit, and in particular, a low power wakeup detection circuit, and a portable electronic device having such wakeup detection circuits. Portable electronic devices may have several power modes: a “full power” mode (also referred to as an “on mode” or “normal” mode) in which normal full functionality of the device is provided; a sleep mode (also referred to as a “low power” mode or “standby” mode) in which reduced functionality of the device is provided; and an “off mode” in which the device is powered-off and performs no functions or a minimized set of functions. To exit the sleep mode or off mode, portable electronic devices having a touch-sensitive display typically periodically scan the touch-sensitive display to detect a touch event. When a touch event is detected, the device switches from the sleep mode or off mode to the full power mode. Periodic scanning of the touch-sensitive display consumes scarce power. The present disclosure provides a wakeup detection circuit which does not require periodic scanning of the touch-sensitive display. The present disclosure also provides a method of waking a portable electronic device and a portable electronic device configured to perform the same.

In accordance with one embodiment, there is provided a method of conserving power on a portable electronic device, the portable electronic device having a device housing which comprises a touch-sensitive display, an accelerometer, and a force sensing transducer, the method comprising: causing the portable electronic device to enter a sleep mode in response to a trigger condition, wherein the touch-sensitive display is deactivated in the sleep mode and the force sensing transducer measures forces applied to the touch-sensitive display at a reduced rate relative to a rate of a full power mode when in the sleep mode; detecting an inertial event using the accelerometer; causing the force sensing transducer to measure forces applied to the touch-sensitive display at the rate of the full power mode in response to detection of an inertial event; detecting forces applied to the touch-sensitive display using the force sensing transducer at the rate of the full power mode; causing the touch-sensitive display to be reactivated in response to detection of a force which is greater than a predetermined wake force threshold; detecting touch events on the touch-sensitive display; and causing the portable electronic device to wake from the sleep mode in response to detection of a touch event within a first predetermined duration of the detection of the force which is greater than a predetermined wake force threshold.

In accordance with another embodiment, there is provided a method of conserving power on a portable electronic device, the portable electronic device having a device housing which comprises a touch-sensitive display and a force sensing transducer, the method comprising: causing the portable electronic device to enter a sleep mode in response to a trigger condition, wherein the touch-sensitive display is deactivated in the sleep mode; detecting forces applied to the touch-sensitive display using the force sensing transducer; causing the touch-sensitive display to be reactivated in response to detection of a force which is greater than a predetermined wake force threshold; detecting touch events on the touch-sensitive display; and causing the portable electronic device to wake from the sleep mode in response to detection of a touch event within a first predetermined duration of the detection of the force which is greater than a predetermined wake force threshold.

In accordance with a further embodiment, there is provided a method of conserving power on a portable electronic device, the portable electronic device having a device housing which comprises a touch-sensitive display, an accelerometer, and a force sensing transducer, the method comprising: causing the portable electronic device to enter a sleep mode in response to a trigger condition, wherein the touch-sensitive display is deactivated in the sleep mode and the force sensing transducer measures forces applied to the touch-sensitive display at a reduced rate relative to a rate of a full power mode when in the sleep mode; detecting an inertial event using the accelerometer;

causing the force sensing transducer to measure forces applied to the touch-sensitive display at the rate of the full power mode in response to detection of an inertial event; detecting forces applied to the touch-sensitive display using the force sensing transducer at the rate of the full power mode; and causing the touch-sensitive display to be reactivated and causing the portable electronic device to wake from the sleep mode in response to detection of a touch event within a first predetermined duration of the detection of the force which is greater than a predetermined wake force threshold.

In accordance with a further embodiment, there is provided a method of conserving power on a portable electronic device, the portable electronic device having a device housing which comprises a touch-sensitive display and an accelerometer, the method comprising: causing the portable electronic device to enter a sleep mode in response to a trigger condition, wherein the touch-sensitive display is deactivated in the sleep mode; detecting an inertial event using the accelerometer; causing the touch-sensitive display to be reactivated in response to detection of an inertial event; detecting touch events on the touch-sensitive display; and causing the portable electronic device to wake from the sleep mode in response to detection of a touch event within a first predetermined duration of the detection of inertial event.

In some embodiments, the portable electronic device comprises a plurality of piezoelectric elements resiliently biased and located beneath the back side of the touch-sensitive display opposite to the touch-sensitive overlay of the touch-sensitive display, the movement of the touch-sensitive display being caused by modulating the charge of the piezoelectric elements thereby providing haptic feedback which simulates the collapse of a dome-type switch. In some embodiments, the plurality of piezoelectric elements comprise four piezoelectric disks, each piezoelectric disk being located near a respective corner of the touch-sensitive display.

In some embodiments in which the portable electronic device comprises a force sensing transducer, the force sensing transducer is located beneath a back side of the touch-sensitive display opposite to a touch-sensitive overlay of the touch-sensitive display, the force sensing transducer measuring forces applied to the touch-sensitive overlay of the touch-sensitive display. In some embodiments, the portable electronic device comprises a plurality of force sensing transducers, wherein a sum of force data measured by the force sensing transducers is used to determine whether an applied force is greater than the predetermined wake force threshold. In some embodiments, the force sensing transducers are force sensing resistors. In some embodiments, the force sensing transducers comprise four force sensing resistors, each force sensing resistor being located near a respective corner of the touch-sensitive display.

In accordance with further embodiments, there is provided a portable electronic device having a device housing in which a controller is received and which comprises a touch-sensitive display, and one or both of an accelerometer or force sensing transducer, the controller being configured to perform any one of the methods described herein.

In accordance with one example embodiment, there is provided a portable electronic device, comprising: a housing; a processor received within the housing; a touch-sensitive display connected to the processor and exposed by the housing, the touch-sensitive display having a touch-sensitive overlay detecting touch events; an accelerometer received within the housing connected to the controller and measuring inertial events; at least one force sensing transducer located below the touch-sensitive display on an opposite side to the touch-sensitive overlay, the at least one force sensing transducer being connected to the controller and measuring forces applied to the touch-sensitive display; wherein the controller is configured for: causing the portable electronic device to enter a sleep mode in response to a trigger condition, wherein the touch-sensitive display is deactivated in the sleep mode and the force sensing transducer measures forces applied to the touch-sensitive display at a reduced rate relative to a rate of a full power mode when in the sleep mode; detecting an inertial event using the accelerometer; causing the force sensing transducer to measure forces applied to the touch-sensitive display at the rate of the full power mode in response to detection of an inertial event; detecting forces applied to the touch-sensitive display using the force sensing transducer at the rate of the full power mode; causing the touch-sensitive display to be reactivated in response to detection of a force which is greater than a predetermined wake force threshold; detecting touch events on the touch-sensitive display; and causing the portable electronic device to wake from the sleep mode in response to detection of a touch event within a first predetermined duration of the detection of the force which is greater than a predetermined wake force threshold.

In accordance with a further embodiment, there is provided a control circuit, comprising: a control circuit, comprising: a controller having a full power duty cycle and a slower sleep mode duty cycle, the full power duty cycle and sleep mode duty cycle each having an active portion in which data is read and an inactive portion in which data is not read; a plurality of force sensing transducers for measuring force data which are connected to the controller; a multi-port switch which sums the force data output of the plurality of force sensing transducers, the multi-port switch having a switch for each of the force sensing transducers, a respective switch for each of the force sensing transducers being closed during an active portion of the sleep duty cycle and the respective switch for each of the force sensing transducers being open during the inactive portion of the sleep duty cycle; and a comparator for comparing the summed force data from the multi-port switch to a wakeup force threshold; wherein the controller is configured to wake from a sleep mode and return to a full power mode when the summed force data is greater than the wakeup force threshold.

In accordance with a further embodiment, there is provided a portable electronic device, comprising: a housing; a controller received within the housing; a touch-sensitive display having a touch-sensitive overlay, the touch-sensitive display being mechanically constrained by the housing; at least one force sensing transducer located below the touch-sensitive display on an opposite side to the touch-sensitive overlay, the at least one force sensing transducer being connected to the controller and measuring forces applied to the touch-sensitive display; wherein the controller is configured for: initiating a sleep mode from a full power mode in response to a trigger; when in the sleep mode, reading force data measured by the at least one force sensing transducer at a reduced duty cycle relative to the full power mode, comparing the force data to a wakeup force threshold, and returning to the full power mode from the sleep mode when the force data is greater than the wakeup force threshold.

In accordance with a further embodiment, there is provided a control circuit, comprising: a controller having a full power duty cycle and a slower sleep mode duty cycle, the full power duty cycle and sleep mode duty cycle each having an active portion in which data is read and an inactive portion in which data is not read; at least one force sensing transducer for measuring force data which is connected to the controller; a switch connected to the at least one force sensing transducer which is closed during an active portion of the sleep duty cycle and open during the inactive portion of the sleep duty cycle; and a comparator for comparing the force data from the switch to a wakeup force threshold; wherein the controller is configured to wake from a sleep mode and return to a full power mode when the force data is greater than the wakeup force threshold.

The disclosure generally relates to an electronic device, which is a portable electronic device in the embodiments described herein. Examples of portable electronic devices include mobile, or handheld, wireless communication devices such as pagers, cellular phones, cellular smart-phones, wireless organizers, personal digital assistants, wirelessly enabled notebook computers, and so forth. The portable electronic device may also be a portable electronic device without wireless communication capabilities, such as a handheld electronic game device, digital photograph album, digital camera, or other device.

A block diagram of an example of a portable electronic device100is shown inFIG. 1. The portable electronic device100includes multiple components, such as a processor102that controls the overall operation of the portable electronic device100. Communication functions, including data and voice communications, are performed through a communication subsystem104. Data received by the portable electronic device100is decompressed and decrypted by a decoder106. The communication subsystem104receives messages from and sends messages to a wireless network150. The wireless network150may be any type of wireless network, including, but not limited to, data wireless networks, voice wireless networks, and networks that support both voice and data communications. A power source142, such as one or more rechargeable batteries or a port to an external power supply, powers the portable electronic device100.

The processor102interacts with other components, such as Random Access Memory (RAM)108, memory110, a display screen112(such as a liquid crystal display (LCD)) with a touch-sensitive overlay114operably connected to an electronic controller116that together comprise a touch-sensitive display118, one or more actuators120, one or more force sensors122, one or more auxiliary input/output (I/O) subsystems124, a data port126, a speaker128, a microphone130, short-range communications subsystem132, and other device subsystems134. It will be appreciated that the electronic controller116of the touch-sensitive display118need not be physically integrated with the touch-sensitive overlay114and display screen112. User-interaction with a graphical user interface is performed through the touch-sensitive overlay114. The processor102interacts with the touch-sensitive overlay114via the electronic controller116. Information, such as text, characters, symbols, images, icons, and other items that may be displayed or rendered on a portable electronic device, is displayed on the touch-sensitive display118via the processor102. The processor102may interact with an accelerometer136that may be utilized to detect direction of gravitational forces or gravity-induced reaction forces. Instead of an accelerometer136, another type of inertial sensor could be used in other embodiments.

The portable electronic device100also includes one or more clocks including a system clock (not shown) and sleep clock (not shown). In other embodiments, a single clock can operate as both system clock and sleep clock. The sleep clock is a lower power, lower frequency clock. By way of example, the system clock may comprise a voltage controlled oscillator operating at a frequency of approximately 700 to 800 megahertz (though the speed of the system clock may vary depending on the mode of the portable electronic device100), whereas the sleep clock may comprise a low power oscillator operating at a frequency in the range of 30 kilohertz to 60 kilohertz. In one example embodiment, the sleep clock operates at 32 kilohertz to reduce the power consumption.

The auxiliary I/O subsystems124could include other input devices such as one or more control keys, a keyboard or keypad, navigational tool (input device), or both. The navigational tool could be a clickable/depressible trackball or scroll wheel, or touchpad. The other input devices could be included in addition to, or instead of, the touch-sensitive display118, depending on the embodiment.

To identify a subscriber for network access, the portable electronic device100uses a Subscriber Identity Module or a Removable User Identity Module (SIM/RUIM) card138for communication with a network, such as the wireless network150. Alternatively, user identification information may be programmed into memory110.

The portable electronic device100includes an operating system146and software programs or components148that are executed by the processor102and are typically stored in a persistent, updatable store such as the memory110. Additional applications or programs may be loaded onto the portable electronic device100through the wireless network150, the auxiliary I/O subsystem124, the data port126, the short-range communications subsystem132, or any other suitable subsystem134.

A received signal such as a text message, an e-mail message, or web page download is processed by the communication subsystem104and input to the processor102. The processor102processes the received signal for output to the display screen112and/or to the auxiliary I/O subsystem124. A subscriber may generate data items, for example e-mail messages, which may be transmitted over the wireless network150through the communication subsystem104. For voice communications, the overall operation of the portable electronic device100is similar. The speaker128outputs audible information converted from electrical signals, and the microphone130converts audible information into electrical signals for processing.

FIG. 2shows a front view of an example of a portable electronic device100in portrait orientation. The portable electronic device100includes a housing200that houses internal components including internal components shown inFIG. 1and frames the touch-sensitive display118such that the touch-sensitive display118is exposed for user-interaction therewith when the portable electronic device100is in use. It will be appreciated that the touch-sensitive display118may include any suitable number of user-selectable features rendered thereon, for example, in the form of virtual buttons for user-selection of, for example, applications, options, or keys of a keyboard for user entry of data during operation of the portable electronic device100.

The touch-sensitive display118may be any suitable touch-sensitive display, such as a capacitive, resistive, infrared, surface acoustic wave (SAW) touch-sensitive display, strain gauge, optical imaging, dispersive signal technology, acoustic pulse recognition, and so forth, as known in the art. A capacitive touch-sensitive display includes a capacitive touch-sensitive overlay114. The overlay114may be an assembly of multiple layers in a stack including, for example, a substrate, a ground shield layer, a barrier layer, one or more capacitive touch sensor layers separated by a substrate or other barrier, and a cover. The capacitive touch sensor layers may be any suitable material, such as patterned indium tin oxide (ITO).

One or more touches, also known as touch contacts or touch events, may be detected by the touch-sensitive display118. The processor102may determine attributes of the touch, including a location of a touch. Touch location data may include an area of contact or a single point of contact, such as a point at or near a centre of the area of contact. The location of a detected touch may include x and y components, e.g., horizontal and vertical components, respectively, with respect to one's view of the touch-sensitive display118. For example, the x location component may be determined by a signal generated from one touch sensor, and the y location component may be determined by a signal generated from another touch sensor. A signal is provided to the controller116in response to detection of a touch. A touch may be detected from any suitable object, such as a finger, thumb, appendage, or other items, for example, a stylus, pen, or other pointer, depending on the nature of the touch-sensitive display118. Multiple simultaneous touches may be detected.

The actuators120comprise one or more piezoelectric devices that provide tactile feedback for the touch-sensitive display118. The actuators120may be depressed by applying sufficient force to the touch-sensitive display118to overcome the actuation force of the actuators120. The actuators120may be actuated by pressing anywhere on the touch-sensitive display118. The actuator120may provide input to the processor102when actuated. Contraction of the piezoelectric actuators applies a spring-like force, for example, opposing a force externally applied to the touch-sensitive display118. Each piezoelectric actuator includes a piezoelectric device, such as a piezoelectric (PZT) ceramic disk adhered to a metal substrate. The metal substrate bends when the PZT disk contracts due to build up of charge at the PZT disk or in response to a force, such as an external force applied to the touch-sensitive display118. The charge may be adjusted by varying the applied voltage or current, thereby controlling the force applied by the piezoelectric disks. The charge on the piezoelectric actuator may be removed by a controlled discharge current that causes the PZT disk to expand, releasing the force thereby decreasing the force applied by the piezoelectric disks. The charge may advantageously be removed over a relatively short period of time to provide tactile feedback to the user. Absent an external force and absent a charge on the piezoelectric disk, the piezoelectric disk may be slightly bent due to a mechanical preload.

The housing200can be any suitable housing for the internal components shown inFIG. 1.FIG. 3Ashows a sectional side view of portions of the portable electronic device100andFIG. 3Bshows a side view of a portion of the actuators120. The housing200in the present example includes a back302, a frame304, which frames the touch-sensitive display118and sidewalls306that extend between and generally perpendicular to the back302and the frame304. A base308is spaced from and is generally parallel to the back302. The base308can be any suitable base and can include, for example, a printed circuit board or flexible circuit board supported by a stiff support between the base308and the back302. The back302may include a plate (not shown) that is releasably attached for insertion and removal of, for example, the power source142and the SIM/RUIM card138referred to above. It will be appreciated that the back302, the sidewalls306and the frame304may be injection molded, for example. In the example of the portable electronic device100shown inFIG. 2, the frame304is generally rectangular with rounded corners, although other shapes are possible.

The display screen112and the touch-sensitive overlay114are supported on a support tray310of suitable material such as magnesium for providing mechanical support to the display screen112and touch-sensitive overlay114. A compliant spacer such as a gasket compliant312is located around the perimeter of the frame304, between an upper portion of the support tray310and the frame304to provide a gasket for protecting the components housed in the housing200of the portable electronic device100. A suitable material for the compliant gasket312includes, for example, a cellular urethane foam for providing shock absorption, vibration damping and a suitable fatigue life. In some embodiments, a number of compliant spacers may be used to provide the function of the gasket compliant312.

The actuators120includes four piezoelectric disk actuators314, as shown inFIG. 4, with each piezoelectric disk actuator314located near a respective corner of the touch-sensitive display118. Referring again toFIGS. 3A and 3B, each piezoelectric disk actuator314is supported on a respective support ring316that extends from the base308toward the touch-sensitive display118for supporting the respective piezoelectric disk actuator314while permitting flexing of the piezoelectric disk actuator314. Each piezoelectric disk actuator314includes a piezoelectric disk318such as a PZT ceramic disk adhered to a metal substrate320of larger diameter than the piezoelectric disk318for bending when the piezoelectric disk318contracts as a result of build up of charge at the piezoelectric disk318. Each piezoelectric disk actuator314is supported on the respective support ring316on one side of the base308, near respective corners of the metal substrate320, base308and housing200. The support316ring is sized such that the edge of the metal substrate320contacts the support ring316for supporting the piezoelectric disk actuator314and permitting flexing of the piezoelectric disk actuator314.

A shock-absorbing element322, which in the present example is in the form of a cylindrical shock-absorber of suitable material such as a hard rubber is located between the piezoelectric disk actuator314and the support tray310. A respective force sensor122is located between each shock-absorbing element322and the respective piezoelectric disk actuator314. A suitable force sensor122includes, for example, a puck-shaped force sensing resistor for measuring applied force (or pressure). It will be appreciated that a force can be determined using a force sensing resistor as an increase in pressure on the force sensing resistor results in a decrease in resistance (or increase in conductance). In the portable electronic device100, each piezoelectric disk actuator314is located between the base308and the support tray310and force is applied on each piezoelectric disk actuator314by the touch-sensitive display118, in the direction of the base308, causing bending of the piezoelectric disk actuator314. Thus, absent an external force applied by the user, for example by pressing on the touch-sensitive display118, and absent a charge on the piezoelectric disk actuator314, the piezoelectric disk actuator314undergoes slight bending. An external applied force in the form of a user pressing on the touch-sensitive display118during a touch event, and prior to actuation of the piezoelectric disk actuator314, causes increased bending of the piezoelectric disk actuator314and the piezoelectric disk actuator314applies a spring force against the touch-sensitive display118. When the piezoelectric disk318is charged, the piezoelectric disk318shrinks and causes the metal substrate320and piezoelectric disk318to apply a further force, opposing the external applied force, on the touch-sensitive display118as the piezoelectric actuator314straightens.

Each of the piezoelectric disk actuators314, shock absorbing elements322and force sensors122are supported on a respective one of the support rings316on one side of the base308. The support rings316can be part of the base308or can be supported on the base308. The base308can be a printed circuit board while the opposing side of the base308provides mechanical support and electrical connection for other components (not shown) of the portable electronic device100. Each piezoelectric disk actuator314is located between the base308and the support tray310such that an external applied force on the touch-sensitive display118resulting from a user pressing the touch-sensitive display118can be measured by the force sensors122and such that the charging of the piezoelectric disk actuator314causes a force on the touch-sensitive display118, away from the base308.

In the present embodiment each piezoelectric disk actuator314is in contact with the support tray310. Thus, depression of the touch-sensitive display118by user application of a force thereto is determined by a change in resistance at the force sensors122and causes further bending of the piezoelectric disk actuators314as shown inFIG. 3A. Further, the charge on the piezoelectric disk actuator314can be modulated to control the force applied by the piezoelectric disk actuator314on the support tray310and the resulting movement of the touch-sensitive display118. The charge can be modulated by modulating the applied voltage or current. For example, a current can be applied to increase the charge on the piezoelectric disk actuator314to cause the piezoelectric disk318to contract and to thereby cause the metal substrate320and the piezoelectric disk318to straighten as referred to above. This charge therefore results in the force on the touch-sensitive display118for opposing the external applied force and movement of the touch-sensitive display118away from the base308. The charge on the piezoelectric disk actuator314can also be removed via a controlled discharge current causing the piezoelectric disk318to expand again, releasing the force caused by the electric charge and thereby decreasing the force on the touch-sensitive display118, permitting the touch-sensitive display118to return to a rest position.

FIG. 5shows a circuit for controlling the actuators120of the portable electronic device100according to one embodiment. As shown, each of the piezoelectric disks318is connected to a controller500such as a microprocessor including a piezoelectric driver502and an amplifier and analog-to-digital converter (ADC)504that is connected to each of the force sensors122and to each of the piezoelectric disks318. In some embodiments, the ADC504could be a 9-channel ADC. The controller500is also in communication with the main processor102of the portable electronic device100. The controller500can provide signals to the main processor102of the portable electronic device100. It will be appreciated that the piezoelectric driver502may be embodied in drive circuitry between the controller500and the piezoelectric disks318.

The mechanical work performed by the piezoelectric disk actuator314can be controlled to provide generally consistent force and movement of the touch-sensitive display118in response to detection of an applied force on the touch-sensitive display118in the form of a touch, for example. Fluctuations in mechanical work performed as a result of, for example, temperature, can be reduced by modulating the current to control the charge.

The controller500controls the piezoelectric driver502for controlling the current to the piezoelectric disks318, thereby controlling the charge. The charge is increased to increase the force on the touch-sensitive display118away from the base308and decreased to decrease the force on the touch-sensitive display118, facilitating movement of the touch-sensitive display118toward the base308. In the present example, each of the piezoelectric disk actuators314are connected to the controller500through the piezoelectric driver502and are all controlled equally and concurrently. Alternatively, the piezoelectric disk actuators314can be controlled separately.

The portable electronic device100is controlled generally by monitoring the touch-sensitive display118for a touch event thereon, and modulating a force on the touch-sensitive display118for causing a first movement of the touch-sensitive display118relative to the base308of the portable electronic device100in response to detection of a touch event. The force is applied by at least one of the piezoelectric disk actuators314, in a single direction on the touch-sensitive input surface of the touch-sensitive display118. In response to determination of a touch event, the charge at each of the piezoelectric disks318is modulated to modulate the force applied by the piezoelectric disk actuators314on the touch-sensitive display118and to thereby cause movement of the touch-sensitive display118for simulating the collapse of a dome-type switch. When the end of the touch event is detected, the charge at each of the piezoelectric disks318is modulated to modulate the force applied by the piezoelectric disk actuators314to the touch-sensitive display118to cause movement of the touch-sensitive display118for simulating release of a dome-type switch.

The touch-sensitive display118is moveable within the housing200as the touch-sensitive display118can be moved away from the base308, thereby compressing the compliant gasket312, for example. Further, the touch-sensitive display118can be moved toward the base308, thereby applying a force to the piezoelectric disk actuators314. By this arrangement, the touch-sensitive display118is mechanically constrained by the housing200and resiliently biased by the compliant gasket compliant312. In at least some embodiments, the touch-sensitive display118is resiliently biased and moveable between at least a first position and a second position in response to externally applied forces wherein the touch-sensitive display118applies a greater force to the force sensors122in the second position than in the first position. The movement of the touch-sensitive display118in response to externally applied forces is detected by the force sensors122.

The analog-to-digital converter504is connected to the piezoelectric disks318. In addition to controlling the charge at the piezoelectric disks318, an output, such as a voltage output, from a charge created at each piezoelectric disk318may be measured based on signals received at the analog to digital converter504. Thus, when a pressure is applied to any one of the piezoelectric disks318causing mechanical deformation, a charge is created. A voltage signal, which is proportional to the charge, is measured to determine the extent of the mechanical deformation. Thus, the piezoelectric disks318also act as sensors for determining mechanical deformation.

FIG. 6shows a block diagram of a circuit600for controlling the force sensors122of the portable electronic device100according to one embodiment of the present disclosure.FIG. 7is schematic diagram of an example circuit according to one embodiment of the present disclosure. The circuit600provides a wakeup detection circuit in some modes including, but not limited to (i) a full power mode in which normal, full functionality of the device100is provided; (ii) a sleep mode in which reduced functionality of the device100is provided; and (iii) an off mode in which the device100is powered-off and performs no functions or a minimized set of functions. As described above, the force sensors122measure the amount of applied force to the touch-sensitive display118(e.g., by the device user's fingers) and the touch-sensitive display118measures the location of touch events. The portable electronic device100described above provides a virtual click or “v-click” touchscreen which uses touch data and force data to generate click or unclick inputs and provide tactile feedback in response to click or unclick inputs using the piezoelectric disks318to actuate the touch-sensitive display118. The touch-sensitive display118is actuated (or moved) up and down in response to the expansion and contraction of the piezoelectric disks318as described above. For convenience, the touch-sensitive display118is sometimes referred to as a touch sensor herein.

The circuit600consists of both analog and digital sections and provides a means of configuring a programmable response of the force sensors122to a user's press against the touch-sensitive display118. In the shown example embodiment, the force sensors122comprise a number of force sensing resistors (FSRs)602for measuring applied force (or pressure). The resistance of the FSRs602change when a force or pressure is applied to them. The change in resistance causes a detectable voltage change. The FSRs602are numbered 1 to n where n is the total number of resistors. As described above in connection withFIG. 3A to 5, in some embodiments four FSRs602are used and located with a piezoelectric disk actuator314near a respective corner of the touch-sensitive display118. The FSRs602may be disk-shaped or puck-shaped and may be located on top of the piezoelectric disks318and below the touch-sensitive display118.

The FSRs602are each controlled by a digitally controlled switch. In the shown embodiment, the FSRs602are connected to an n-port switch604(also known as a multi-port switch) which comprises n single-pole, single-throw (SPST) switches. In embodiments in which four FSRs602are used, the n-port switch604comprises four SPST switches, one for each FSR602. The n-port switch604controls which, if any, of the FSRs602report force data to host processor102(directly or indirectly). The n-port switch604and SPST switches are controlled by the controller500ofFIG. 5.

The n-port switch604generates an output signal which is sent to a signal conditioning circuit or module606of the circuit600. The signal conditioning module606can be used to offset (or bias) the FSRs602at various levels under the control of the controller500. The signal conditioning module606can also be used to vary the sensitivity of the FSR response by varying the gain provided by the signal conditioning module606. The controller500controls the variable offset and gain of the signal conditioning module606. In at least some embodiments, the signal conditioning module606comprises digital potentiometers which are controlled by the controller500and utilized for adjusting and calibrating the response of the FSRs602and an operational amplifier (Op-Amp), while in other embodiments, analog potentiometers could be used. In other embodiments, the signal conditioning module606could be omitted depending on the configuration of the FSRs602or other force sensor122used in the circuit600.

Typically, the FSRs602are pre-loaded with an amount of force as a result of the mechanical forces applied by the housing200and touch-sensitive display118. The amount of pre-loading may vary between embodiments. The bias and gain of the FSRs602can be calibrated to account for the pre-loading and FSR sensitivity differences using the signal conditioning module606, for example, using potentiometers. In the shown embodiment, the circuit600can be used to calibrate each FSR602individually by closing the respective switch in the n-port switch604.

In other embodiments, rather than summing all of the FSRs602via the n-port switch604groups of FSRs602may be summed and evaluated independently. For example, when four FSRs602are used near the respective corners of the touch-sensitive display108, the top pair of FSRs602and bottom pair of FSRs602could be summed and evaluated independently (e.g., groups of two FSRs602could be evaluated). These groupings could shift depending on whether the portable electronic device is in a portrait or landscape orientation. Alternatively, the left side and right sight FSRs602could be summed and evaluated independently. In yet other embodiments, individual FSRs602could be read/scanned and evaluated independently. A force event could be triggered (e.g. for a wakeup event) if all, any group or pair, or any one of the FSRs602measured a force which exceeds the predetermined wake force/pressure threshold. In other embodiments, other force sensing transducers comprising a force sensor such as a strain gauge or pressure sensor could be used to detect a force event (e.g. an applied force against the touch-sensitive display which exceeds the predetermined wake force/pressure threshold) instead of FSRs602. Alternatively, the piezoelectric disk actuators314could be used to detect a force event.

The controller500, in the shown embodiment ofFIG. 6, includes a General Purpose Input/Output (GPIO). A GPIO is an interface which can act as input to read digital signals from other parts of the circuit600such as the signal conditioning module606, or output digital signals to other parts of the circuit. The GPIO may be provided by a GPIO port having a number of individual GPIOs configurable as either input or outputs, and may be configurable to produce interrupts to the host processor102. The controller500also includes an ADC504(FIG. 5) with a corresponding interface as described above. Alternatively, the controller500or signal conditioning block606could incorporate an analog comparator with a programmable reference for achieving the same. In some example embodiments, the controller500could be the electronic controller116of the touch-sensitive display118or the processor102.

The portable electronic device100has several power modes: (i) a full power mode in which normal, full functionality of the device100is provided; (ii) a sleep mode in which reduced functionality of the device100is provided; and (iii) an off mode in which the device100is powered-off and performs no functions or a minimized set of functions. The sleep mode may be triggered by any one of a number of possible trigger conditions. The portable electronic device100monitors for one or more predetermined trigger conditions for entering the sleep mode. The one or more trigger conditions may be include any one or more of a selection of a sleep/standby option or device lock option via corresponding input, user inactivity for a predetermined duration, lack of wireless network coverage for a predetermined duration, a holstering or closing of the portable electronic device100, or other suitable trigger condition. In response to detection of a trigger condition, the processor102initiates the sleep mode and notifies the controller500to initiate a sleep mode for the circuit600. The controller500then proceeds to read (scan) the FSRs602for a wakeup event until either a wakeup force/pressure threshold is met, or the processor102signals the controller500to cease reading/scanning the FSRs602. When the wakeup force threshold is exceeded, the controller500can signal an interrupt back to the processor102waking it from the sleep mode (or standby state).

In some embodiments, when in the sleep mode, power consumption is conserved by powering off the high frequency system clock and switching the controller500from the system clock to the sleep clock. This reduces the power consumption of the circuit600. In the sleep mode, the sleep clock is used by the controller500and the host processor102is idle.

The controller500uses a sleep clock to schedule “on” and “off” time of the circuit600accordance with a predetermined duty cycle. The duty cycle is programmable and controls the balance between power consumption and response latency. In some embodiments, the n-port switch604is closed and the FSRs602are powered “on” for approximately 1 millisecond every 100 milliseconds. During this time, the controller500reads the FSRs602to detect force events, that is, to determine if a force greater than a predetermined amount of applied force (i.e., a force threshold) is read by one or more of the FSRs602. After being powered-on for approximately 1 millisecond during the “on” time, the FSRs602are powered-off for 99 milliseconds by re-opening the n-port switch604for “off” time or inactive portion of the duty cycle. The FSRs602are powered-off for the remainder of the duty cycle.

The duration of the duty cycle may be selected to configure the duration of a force applied to the touch-sensitive display118(e.g., screen press) required to trigger a force event. For example, in some embodiments the duration of time which the FSRs602are read is configured to detect a “push and hold” or “press and hold” action caused by the device user pressing a finger against the touch-sensitive display118and holding it against the touch-sensitive display118for a predetermined duration such as, for example, approximately 100 milliseconds. The predetermined duration for a press and hold may be programmable/configurable, for example, to tune the wakeup function to the device user's habits or preferences and to filter out small ambient vibrations from normal movements, such as the device user walking with the device100. For example, an inertial event caused by a tap event would occur and be over within a few milliseconds, e.g. approximately 20-25 milliseconds or less. The predetermined duration for a press and hold action is set to be longer than that of a typical tap event such as, for example, approximately 100 milliseconds. However, the predetermined duration could be more or less than 100 milliseconds and would typically be less than one second, and possibly less than 500 milliseconds. This means that any inertial event would have ended when the predetermined duration for detecting a press and hold event is reached. The touch-sensitive display118should also detect a tap event of the predetermined duration at the same time. Due to latency issues the forces measured by the force sensors122and the touches measures by the touch-sensitive display118may not be reported at the same time, however, these events can be synchronized or matched with each other.

In the shown example embodiment, the controller500configures the n-port switch604to sum the measurement of all of the FSRs602by closing each of the 4 SPST switches of the n-port switch604which are normally open, thereby connecting the FSRs602in parallel. The resultant output signal of the n-port switch604is then fed as input into the signal conditioning module606. The variable offset and gain provided by the signal conditioning module606allows for a programmable response from the FSRs602, thereby controlling the predetermined amount of applied force (i.e., force threshold) which is needed to trigger a force event.

As a result of summing of the readings of the FSRs602and a properly set force threshold, it is possible to trigger a force event when a device user presses on the touch-sensitive display118at any location. This occurs because a screen press under these conditions causes a force greater than or equal to the predetermined amount of applied force (i.e., the force threshold) to be detected on at least one of the FSRs602. The force event will typically be detected by the FSR602closest to the location of the applied force on the touch-sensitive display118and possibly one or more of the other FSRs602.

Force events are defined by applied forces greater than the force threshold. Force events can be detected using either analog or digital threshold comparator depending on the embodiment. In some embodiments, the analog signal output by the signal conditioning module606can be digitized by an ADC and then evaluated with a digital threshold comparator which can be implemented either in hardware or in software. For example, in some embodiments, force events could be detected by the controller's internal ADC504detecting that the analog signal has exceeded the force threshold. In other embodiments, force events could be detected by an analog comparator circuit (not shown) which triggers an interrupt to the controller500when the analog signal output by the signal conditioning module606exceeds the force threshold. The analog comparator can detect and signal a high/low output to the processor102. When a force event is detected, the controller500sends a signal to the host processor102of the device100that an interrupt event was detected, and brings the portable electronic device100out of the sleep mode and into the full power mode. Wakeup events are defined by applied forces greater than a predetermined wakeup force threshold.

The described method of wakeup uses a relatively small amount of power while still allowing wakeup events to be detected. This functionality also reproduces the wakeup of a portable electronic device100caused by the collapse of a dome-type switch disposed between the touch-sensitive display118and housing200when the device user presses any where on the touch-sensitive display118.

FIG. 8shows a flowchart illustrating a method800of providing a sleep mode on the portable electronic device100and waking up the device100from the sleep mode in accordance with one example embodiment. The steps ofFIG. 8may be carried out by routines or subroutines of software executed by, for example, the processor102. The coding of software for carrying out such steps is well within the scope of a person of ordinary skill in the art given the present disclosure. For example, the sleep mode may be implemented by a sleep process which operates in the background as part of the operating system146.

In the first step802, the processor102monitors for one or more predetermined trigger conditions for entering the sleep mode. The one or more trigger conditions may be include any one or more of a selection of a sleep/standby option via corresponding input or possibly a device lock option via corresponding input, user inactivity for a predetermined duration, lack of wireless network coverage for a predetermined duration, a holstering or closing of the portable electronic device100, or other suitable trigger condition.

When one of the trigger conditions for entering the sleep mode is detected, the processor102initiates the sleep mode (step804). The sleep mode may comprise the processor102switching from the system clock to the sleep clock and deactivating (e.g., powering off) the touch-sensitive display118. When deactivated, the touch-sensitive display118does not measure touch data or detect touch events and its backlight is deactivated/disabled. In the sleep mode, the force sensors122continue to detect and measure forces applied to the touch-sensitive display118. In at least some embodiments, the processor102instructs the controller500to initiate a sleep mode for the force sensor circuit600when one of the trigger conditions for entering the sleep mode is detected. In the sleep mode, the force sensors122operate at a reduced duty cycle relative to the full power mode and/or sample at a lower sampling rate relative to the full power mode to consume less power.

A locked mode may also be initiated in response to detecting one of the trigger conditions for entering a sleep mode when the sleep mode is itself triggered by a locking process, depending on the configuration of the locking process. In the locked mode, restrictions limiting interaction with the portable electronic device100are enforced. The restrictions typically affect at least some of its input interfaces/devices (e.g., overlay114, auxiliary I/O124, accelerometer136) and at least some of its output interfaces/devices (e.g., display screen112, speaker128).

To reduce the power and resources consumed by the force sensor circuit600, touch-sensitive display118and the host processor102, the force sensors122and touch-sensitive display118can be put in a low reporting mode in which data is provided to the processor102only when a change in state of the respective sensor occurs. The low reporting mode can be contrasted with a full reporting mode in which the force sensors122and touch-sensitive display118provide data at regular scanning cycles irrespective of the state of the respective sensor. For the touch sensor118, a change in the location of a touch event greater than a predetermined threshold or a change number of touches will trigger a change of state. For the force sensors122, a change in state occurs when a force greater than a predetermined force threshold is detected by the force sensor controller500on all, any group or pair, or any one of the force sensors122. A force greater than the predetermined force threshold is assumed to be a user finger applied to the touch-sensitive display118. The predetermined force threshold for trigger a change in state is different from, and less than, the predetermined wake force threshold mentioned above.

In some embodiments, the sleep mode comprises changing the sampling of the force sensors122from the full reporting mode to the low reporting mode to consume less power. However, in other embodiments, the low reporting mode may be used by the force sensor122and possibly the touch-sensitive display118in both the full power mode and the sleep mode.

Next, in step806the force sensor controller500reads the force data output by the force sensors122and detects any wakeup force. The wakeup force is a force greater than the predetermined wake force threshold. This can be performed using analog or digital means as described above. When a wakeup force is detected, the force sensors122(e.g., and the circuit600) wakeup from the sleep mode and return to the normal duty cycle and/or normal sampling rate of the full power mode, and touch-sensitive display118is reactivated (powered-up) so that touch data can be read/sampled for a predetermined duration (step808). In other embodiments, the force sensors122could be maintained at the lower sampling rate of the sleep mode to consume less power when the touch-sensitive display118is reactivated. The force data and touch data are then read and it is determined whether a screen press or “click” has occurred or is in progress.

The backlight of the touch-sensitive display118may or may not be reactivated during the scanning/reading of the touch-sensitive display118which occurs in response to detection of a wakeup force, depending on the embodiment. For example, in some embodiments the backlight of the touch-sensitive display118is not activated until the wakeup event is confirmed by touch data read by the touch-sensitive display118to conserve power.

When the force data read by the forces sensors122and the touch data read by the touch-sensitive display118indicates a screen press or “click” has occurred or is in progress (step810), the processor102wakes up from the sleep mode and returns to full power mode (step812). If the processor102was switched from the system clock to the sleep clock during the sleep mode, the processor102switches back to the system clock. Other changes made when entering the sleep mode are also reversed. In at least some embodiments, the charge at each of the piezoelectric disks318is then be modulated to modulate the force applied by the piezoelectric disk actuators314on the touch-sensitive display118and to thereby cause movement of the touch-sensitive display118for simulating the collapse of a dome-type switch. This provides tactile or haptic feedback to the device user so that they know a screen press or “click” was registered by the device100.

If a screen press or “click” is not detected, the touch-sensitive display118is deactivated again until being reactivated by the detection of another wakeup force, and the force sensors122are returned to the lower duty cycle and/or lower sampling rate of the sleep mode.

As will be appreciated by persons skilled in the art, sampling forces and touches applied to the touch-sensitive display118consumes scarce device power. During normal operation, this sampling occurs at a high rate to keep up with user interaction with the touch-sensitive display118. However, when the portable electronic device100is idle a high sampling rate needlessly consumes power resulting in a shorter life for the power source142. The present disclosure provides a method and portable electronic device100which aims to minimize, or at least reduce, the power consumed when the portable electronic device100while still clicking in response to forces.

To reduce the power and processing resources consumed, the present disclosure provides a sleep mode which deactivates the touch-sensitive display118when the device100is idle and uses the force sensors122to sample force data at a lower sampling rate to detect a potential wakeup when a force greater than the predetermined wakeup force threshold is detected. The sleep mode described in the present disclosure aims to minimize, or at least reduce, the power consumed when the portable electronic device100is idle while also registering screen presses or “clicks” in response to applied forces and optionally providing tactile/haptic feedback by modulating the charge at each of the piezoelectric disks318to modulate the force applied by the piezoelectric disk actuators314.

Moreover, the predetermined wakeup force threshold may be set so as to filter out small applied forces such as ambient forces resulting from normal movements of the portable electronic device100(such as those applied to the device100while in a user's pocket while walking), while still detecting a finger pressing against touch-sensitive display118. This avoids unnecessary wakeup event checks by limiting the applied forces which will be detected as potential wakeup events.

FIG. 9shows a flowchart illustrating a method900of providing a sleep mode on the portable electronic device100and waking up the device100from the sleep mode in accordance with another example embodiment. The steps ofFIG. 9may be carried out by routines or subroutines of software executed by, for example, the processor102. The coding of software for carrying out such steps is well within the scope of a person of ordinary skill in the art given the present disclosure. For example, the sleep mode may be implemented by a sleep process which operates in the background as part of the operating system146.

In steps802and804, the processor102monitors for one or more trigger conditions for enter a sleep mode, and enters a sleep mode in response to detection of one of the trigger conditions as described above. In the sleep mode of the embodiment shown inFIG. 9, the forces sensors122are not read by the controller500. As a result, the force sensors122or the entire circuit600may be powered-off to consume less power. In some embodiments, the circuit600has a non-power cycled current draw of approximately 80 μA which can be reduced by powering down the forces sensors122. In other embodiments, the force sensors122could be operated at a reduced/slower duty cycle relative to the full power mode and/or sample at a lower sampling rate relative to the full power mode to consume less power as in the method800ofFIG. 8.

Next, in step902the accelerometer136is used to detect an inertial event. The inertial event could be a tap on the touch-sensitive display118, a movement of the device100causing a change in acceleration which exceeds a predetermined threshold, or possible a predetermined movement or gesture performed by moving the device100in a predetermined manner (this motion being detected by the accelerometer136).

A gesture is a predetermined motion performed by moving the device100in a predetermined manner such as a predetermined direction or series of directions. Gestures are identified by comparing the accelerations measured by the accelerometer136to reference data for the predetermined motions to determine whether the detected motion is characteristic of one of the predetermined motions. This is typically performed by the host processor102using acceleration data provided by the accelerometer136, but could be performed via a built-in electronic controller of the accelerometer136. The predetermined inputs could be a forward movement, backward movement, up movement, down movement, left movement, right movement, tilt left movement, tilt right movement, swing left movement, swing right movement or any other predetermined movement such as a movement which approximate a letter, number of symbol, or a series of such movements. In some embodiments, a horizontal tilt or swing movement (i.e., a left or right horizontal tilt or swing movement) and vertical tilt or swing movement (i.e., an up or down tilt or swing movement). Alternatively, a left tilt or swing movement, right tilt or swing movement, up tilt or swing movement and down tilt or swing movement could each be distinct predetermined inputs.

In some example embodiments, the inertial event could be a tap on the touch-sensitive display118and the accelerometer136is a digital accelerometer having a built-in tap detection function which may be used to detect a tap on the touch-sensitive display118. Many commercially available digital accelerometers have a built-in tap detection function. Any digital accelerometer having a built-in tap detection function could be used. The tap detect threshold used by the built-in tap detection function may be programmable/configurable and set so as to filter out small ambient vibrations from normal movements, such as the device user walking with the device100.

Alternatively, rather than a digital accelerometer an analog accelerometer with an analog comparator circuit (not shown) with a programmable/configurable reference could be used. The programmable reference acts as a predetermined acceleration threshold for an inertial event. The analog comparator circuit sends an interrupt to the controller500when the analog output signal of the analog accelerometer exceeds the programmable reference.

The accelerometer136may also be power-cycled to lower the sampling rate and conserve power when the device100is idle, for example, when the acceleration reading has not changed by more than a predetermined amount for a predetermined duration. Power-cycling of the accelerometer136may occur automatically as part of entering the sleep mode. When the acceleration exceeds this amount, the accelerometer136returns to the higher sampling rate to reduce latency in detection acceleration. In some example embodiments, the accelerometer136could have autonomous power cycling that can reduce current consumption to approximately 25 μA or less.

When an inertial event is detected, an interrupt is sent from the accelerometer136or a comparator circuit for the accelerometer136to the controller500to wake the force sensors122(step904). As noted above, waking the force sensors122may comprise powering on the force sensors122, increasing from a lower sampling rate of the sleep mode to a higher sampling rate (e.g., normal sampling rate of the full power mode), depending on the configuration of the sleep mode. Alternatively, the interrupt could be sent to the host processor102, or to both the controller500and processor102.

Next, in step806the force data output by the force sensors122is read by the force sensor controller500of the circuit600which detects any wakeup force. This can be done via analog or digital means as described above. In some embodiments in which sleeping and waking the force sensors122comprises powering down and powering up the force sensors, the process of powering up the force sensors122and taking a measurement may take approximately 1 millisecond or less depending on the design of the signal conditioning module606. This amount of time is sufficiently short that a wakeup force caused by an inertial event should, in at least most circumstances, still be present when the force sensors122wake. If no wakeup force is present when the force sensors122wake, the inertial event is considered to be erroneous and caused by something other than a screen press or “click”.

When a wakeup force is detected, the touch-sensitive display118is reactivated/powered-up and the processor102wakes up from the sleep mode and returns to full power mode (step812). If the processor102was switched from the system clock to the sleep clock during the sleep mode, the processor102switches back to the system clock. Other changes made to when entering the sleep mode are also reversed. In at least some embodiments, the charge at each of the piezoelectric disks318is modulated to modulate the force applied by the piezoelectric disk actuators314on the touch-sensitive display118and to thereby cause movement of the touch-sensitive display118for simulating the collapse of a dome-type switch. This provides tactile or haptic feedback to the device user so that they know a screen press or “click” was registered by the device100.

If a wakeup force is not detected, the force sensors122are deactivated/powered-off again and returned to the sleep mode until being reactivated by the detection of another inertial event.

The method900provides a wakeup solution which uses inertial events to trigger a device wakeup and a force event to verify this trigger. The inertial event could be a movement of the device100or a tap on the touch-sensitive display118. For example, in some embodiments the device could be configured to use a “press and hold” event as a wakeup event. In a press and hold event, the user presses or taps on the touch-sensitive display118with a finger to create an inertial event and presses on the touch-sensitive display118for a predetermined duration to create a force event. The touch-sensitive display118should also detect a tap event of the predetermined duration at the same time. Due to latency issues the forces measured by the force sensors122and the touches measures by the touch-sensitive display118may not be reported at the same time, however, these events can be synchronized or matched with each other. The inertial event will have ended when the predetermined duration for detecting a press and hold event is reached. The press and hold event will trigger a wakeup as described above.

In an alternate embodiment, the force sensors122are not affected by the sleep mode. In the sleep mode, the touch-sensitive display118and host processor102are put to sleep as described above and the accelerometer136is used to monitor for inertial events which, when detected, trigger an increase in the duty cycle and/or sampling rate of the force sensors122in order to reduce the latency in detecting wakeup events in the form of force events.

FIG. 10shows a flowchart illustrating a method920of providing a sleep mode on the portable electronic device100and waking up the device100from the sleep mode in accordance with a further example embodiment. The steps ofFIG. 10may be carried out by routines or subroutines of software executed by, for example, the processor102. The coding of software for carrying out such steps is well within the scope of a person of ordinary skill in the art given the present disclosure. For example, the sleep mode may be implemented by a sleep process which operates in the background as part of the operating system146.

The method920comprises the steps802,804,902,904and806described above in connection with the method900ofFIG. 9. However, the force sensors122measure force at a reduced rate in the sleep mode as in the method800ofFIG. 8. When a wakeup force is detected, the force sensors122(e.g., and the circuit600) wakeup from the sleep mode and return from a reduced duty cycle of the sleep mode to the normal duty cycle and/or normal sampling rate of the full power mode, and touch-sensitive display118is reactivated (powered-up) so that touch data can be read/sampled for a predetermined duration (step808).

When the force data read by the forces sensors122and the touch data read by the touch-sensitive display118indicates a screen press or “click” has occurred or is in progress (810), the processor102wakes up from the sleep mode and returns to full power mode (step812). If the processor102was switched from the system clock to the sleep clock during the sleep mode, the processor102switches back to the system clock. Other changes made when entering the sleep mode are also reversed. In at least some embodiments, the charge at each of the piezoelectric disks318is then be modulated to modulate the force applied by the piezoelectric disk actuators314on the touch-sensitive display118and to thereby cause movement of the touch-sensitive display118for simulating the collapse of a dome-type switch. This provides tactile or haptic feedback to the device user so that they know a screen press or “click” was registered by the device100.

If a screen press or “click” is not detected, the touch-sensitive display118is deactivated again until being reactivated by the detection of another wakeup force, and the force sensors122are returned to the lower duty cycle and/or lower sampling rate of the sleep mode.

The method920is similar to the method800ofFIG. 8but adds inertial event detection using the accelerometer136from the method900ofFIG. 9to verify potential wakeup events which an aim to reduce the false “wakeups” which may result, for example, from a finger moving across the touch-sensitive display118.

In an alternate embodiment, the force sensors122are not affected by the sleep mode. In the sleep mode, the touch-sensitive display118is deactivated and host processor102is idled as described above and the accelerometer136is used to monitor for inertial events which, when detected, trigger an increase in the duty cycle and/or sampling rate of the force sensors122in order to reduce the latency in detecting wakeup events in the form of force events. In another alternate embodiment, detection of the inertial event could wake both the force sensors122and touch-sensitive display118at the same time.

In some embodiments, the detection of an inertial event could cause the duty cycle and/or the sampling rate of the touch-sensitive display118to be increased to reduce the latency in wakeup event detection caused by the relatively long scan cycle of the touch-sensitive display118.

FIG. 11shows a flowchart illustrating a method940of providing a sleep mode on the portable electronic device100and waking up the device100from the sleep mode in accordance with a further example embodiment. The steps ofFIG. 11may be carried out by routines or subroutines of software executed by, for example, the processor102. The coding of software for carrying out such steps is well within the scope of a person of ordinary skill in the art given the present disclosure. For example, the sleep mode may be implemented by a sleep process which operates in the background as part of the operating system146.

The method940comprises the steps802,804and902as described above. However, the detection of an inertial event is used to reactivate (power-up) the touch-sensitive display118so that touch data can be read/sampled for a predetermined duration (step808) rather than waking up force sensors122. The force sensors122are not used in the process940and could be omitted from a device100which implements this method. When the touch data read by the touch-sensitive display118indicates a touch event has occurred or is in progress (step910), the processor102wakes up from the sleep mode and returns to full power mode (step812). If the processor102was switched from the system clock to the sleep clock during the sleep mode, the processor102switches back to the system clock. Other changes made when entering the sleep mode are also reversed. The charge of the piezoelectric disks318is not modulated and no tactile or haptic feedback is provided to the device user. In such embodiments, the force sensors122and actuators120(e.g. piezoelectric disk actuators314) could be omitted.

If a touch event is not detected (step810), the touch-sensitive display118is deactivated again until being reactivated by the detection of another inertial event.

The method940is similar to the method900ofFIG. 9but does not use the force sensors122to detect wakeup events. Instead, the inertial event detection function provided by the accelerometer136is used to wake the touch-sensitive display118, and the touch data measured by the touch-sensitive display118is used verify potential wakeup events which an aim to reduce the false “wakeups” which may result from using only the inertial event detection function as a wakeup event. That is, a touch event must be detected within a predetermined duration of when the touch-sensitive display118wakes up. The charge of the piezoelectric disks318is not modulated and no tactile or haptic feedback is provided to the device user.

The present disclosure teaches a method and portable electronic device which combines measurements from two or more independent sensors to confirm the detection of a wakeup event for a portable electronic device100, thereby reducing false-positives. In some embodiments, such as the method800, force data provided by force sensors122is combined with touch data provided by a touch-sensitive display118to verify potential wakeup events with an aim to reduce the false “wakeups”.

In some embodiments, such as the method900and920, inertial event detection provided by the accelerometer136is combined with force data provided by the force sensors122to verify potential wakeup events which an aim to reduce the false “wakeups” which may result from a finger moving across the touch-sensitive display118. The time correlation of the interrupt signal from the threshold crossing event of accelerometer136and the interrupt signal from the threshold crossing event of force sensors122may be used to reliably detect a device wakeup event at relatively low power and complexity.

In some embodiments, such as the method900and920, the power draw of the sleep mode may be reduced by powering off both the touch-sensitive display18and force sensors122while powering only the accelerometer136. In some embodiments, further power savings may be realized by power cycling the accelerometer136.

The various embodiments presented above are merely examples and are in no way meant to limit the scope of this disclosure. Variations of the innovations described herein will be apparent to persons of ordinary skill in the art, such variations being within the intended scope of the present application. In particular, features from one or more of the above-described embodiments may be selected to create alternative embodiments comprised of a sub-combination of features which may not be explicitly described above. In addition, features from one or more of the above-described embodiments may be selected and combined to create alternative embodiments comprised of a combination of features which may not be explicitly described above. Features suitable for such combinations and sub-combinations would be readily apparent to persons skilled in the art upon review of the present application as a whole. The subject matter described herein and in the recited claims intends to cover and embrace all suitable changes in technology.