U.S. patent application number 14/035240 was filed with the patent office on 2014-07-10 for stylus and related human interface devices with dynamic power control circuits.
This patent application is currently assigned to CYPRESS SEMICONDUCTOR CORPORATION. The applicant listed for this patent is CYPRESS SEMICONDUCTOR CORPORATION. Invention is credited to Victor Kremin, Andriy Ryshtun, David G. Wright.
Application Number | 20140192030 14/035240 |
Document ID | / |
Family ID | 51031787 |
Filed Date | 2014-07-10 |
United States Patent
Application |
20140192030 |
Kind Code |
A1 |
Ryshtun; Andriy ; et
al. |
July 10, 2014 |
STYLUS AND RELATED HUMAN INTERFACE DEVICES WITH DYNAMIC POWER
CONTROL CIRCUITS
Abstract
A device comprising a body comprising an elongated housing with
at least a first conductive tip formed at a distal end and at least
one sense electrode on the body; a capacitance sense circuit
disposed within the housing and configured to sense a capacitance
of the sense electrode to generate a proximity result in response
to contact with a human body; and a signal generator circuit
disposed within the housing and configured to activate a position
signal in response to the proximity result, the position signal
being driven at the tip of the device
Inventors: |
Ryshtun; Andriy; (Lviv,
UA) ; Kremin; Victor; (Lviv, UA) ; Wright;
David G.; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CYPRESS SEMICONDUCTOR CORPORATION |
San Jose |
CA |
US |
|
|
Assignee: |
CYPRESS SEMICONDUCTOR
CORPORATION
San Jose
CA
|
Family ID: |
51031787 |
Appl. No.: |
14/035240 |
Filed: |
September 24, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61751146 |
Jan 10, 2013 |
|
|
|
Current U.S.
Class: |
345/179 |
Current CPC
Class: |
G06F 3/038 20130101;
G06F 3/03545 20130101; G06F 1/325 20130101; G06F 1/3206 20130101;
H03K 17/955 20130101 |
Class at
Publication: |
345/179 |
International
Class: |
G06F 3/0354 20060101
G06F003/0354 |
Claims
1. A device, comprising: a body comprising an elongated housing
with at least a first conductive tip formed at a distal end and at
least one sense electrode on the body; a capacitance sense circuit
disposed within the housing and configured to sense a capacitance
of the sense electrode to generate a proximity result in response
to contact with a human body; and a signal generator circuit
disposed within the housing and configured to activate a first
position signal in response to the proximity result and a second
position signal, different from the first position signal, in
response to sensing a force at the tip, the first and second
position signals being driven at the tip of the device, and the
first position signal having a greater magnitude than the second
position signal.
2. The device of claim 1, wherein: the body comprises a single
structure that includes the sense electrode.
3. The device of claim 1, wherein: the body comprises a
non-conductive material and the sense electrode comprises a
conductive material formed on the non-conductive material.
4. The device of claim 3, wherein: the sense electrode comprises a
conductive polymer.
5. The device of claim 1, wherein: the capacitance sense circuit
comprises an integrator circuit that integrates a sense signal;
wherein the sense signal and first and second position signals are
time varying signals.
6. The device of claim 5, wherein: the sense signal is selected
from the first or second position signals.
7. The device of claim 5, wherein: the sense signal has a lower
frequency than the first and second position signal in at least one
mode.
8. A device, comprising: a body comprising an elongated housing
with at least a first conductive tip formed at a distal end and at
least one sense electrode on the body; a sense circuit disposed
within the housing and configured to detect a human body in
proximity to the sense electrode to generate a proximity result;
and a controller configured to switch the device between a low
power mode and an active mode in response to at least the proximity
result; a signal generator circuit configured to drive the tip with
a first position signal or a second position signal, the second
position signal being driven in response to a force applied at the
tip of the device; wherein the device consumes less power in the
low power mode as compared to the active mode, and the first
position signal has a greater magnitude than the second position
signal.
9. The device of claim 8, further including: the signal generator
circuit is further configured to drive the first position signal at
the tip of the device in the active mode, and to disable the first
position signal at the tip in the low power mode.
10. The device of claim 9, further including: a modulator circuit
configured to modulate at least the first position signal according
to data values in the active mode, the modulator circuit being
disabled in the low power mode.
11. The device of claim 8, further including: a force measurement
circuit configured to generate a force value according to a
mechanical force applied at the tip of the device in the active
mode, the force measurement circuit being disabled in the low power
mode.
12. The device of claim 11, further including: the first and second
position signals are time varying signals.
13. The device of claim 11, further including: a shield electrode
formed on the housing adjacent to the tip; and the signal generator
circuit drives the shield electrode and tip with the second
position signal when a force is detected at the tip, and drives the
tip with the first position signal and grounds the shield electrode
when the force is not detected at the tip.
14. The device of claim 8, further including: the signal generator
circuit is further configured to drive the sense electrode and the
tip with the first position signal in the active mode, and in the
low power mode, drive the sense electrode with a sense signal and
not drive the tip with the first position signal.
15. The device of claim 8, further including: at least one button;
and the controller is configured to switch the device between the
low power mode and the active mode in response to at least an
activation of the button.
16. A method, comprising: capacitance sensing a proximity of at
least a portion of a human body with a sense electrode formed on a
surface of an input device, the input device having an elongated,
hollow body and at least one distal tip; selectively generating a
position signal at the tip with circuits within the body; switching
between a lower power mode and an active mode in response to the
capacitance sensing of the sense electrode with circuits within the
body; and switching from a generating a first position signal at
the tip to generating a second position signal at the tip in
response to sensing a force at the tip; wherein the device consumes
less power in the low power mode as compared to the active mode,
and the first position signal has a greater magnitude than the
second position signal.
17. The method of claim 16, further including: generating the
position signal at the tip in the active mode and not generating
the position signal at the tip in the low power mode.
18. (canceled)
19. The method of claim 16, further including: in the active mode,
sensing a force applied at the tip; in response to one type of
sensed force, generating the first position signal at the tip and
at a shield electrode, the shield electrode being different than
the sense electrode; and in response to another type of sensed
force, generating the second position signal at the tip and
disconnecting the shield electrode from any position signal.
20. The method of claim 16, further including: after switching to
the active mode, returning to the low power mode if a proximity of
at least a portion of the human body is not sensed for a
predetermined period of time.
Description
[0001] This application claims the benefit of U.S. provisional
patent application Ser. No. 61/751,146 filed on Jan. 10, 2013, the
contents of which are incorporated by reference herein.
TECHNICAL FIELD
[0002] The present disclosure relates generally to human interface
devices, and more particularly to styluses and related pointing
devices.
BACKGROUND
[0003] The use of a stylus with touchscreens is well known, but
existing technologies can have the disadvantages of cost,
performance and/or reliability. Resistive touchscreens can be well
suited for use with a passive (i.e., non-powered) stylus. The
PalmPilot personal digital assistant (PDA), launched in 1997, was
one of the first devices with a resistive touchscreen designed for
use with a stylus, and helped to popularize that technology.
However, resistive touchscreens have many disadvantages, and are
increasingly being replaced by capacitive touchscreens.
[0004] Capacitive touchscreens can support the use of a passive
stylus, but in many cases, can require a minimum stylus tip size
(e.g., 5 mm). Such a size can be much larger than a pen-like tip
(e.g., 1 mm) desired in many applications.
[0005] Various tethered active (i.e., powered) stylus approaches
have been deployed for use with capacitive touchscreens, and have
been included in applications such as point-of-sale terminals
(e.g., the signature pad used for credit card transactions in
larger retail stores) and other public uses. However, the need for
a cable (i.e., that tethers the stylus to a host device) can be a
significant drawback for "private" applications such as tablets,
personal computers (PCs), and smartphones.
[0006] Conventional technologies used in tethered applications can
fall broadly into two categories: inductive and electrostatic. In
inductive technologies, stylus sensing is implemented largely
independently of the finger-sensing capability of the touchscreen.
Typically, an AC signal is generated and fed to the tip of the
stylus, and sensors behind or around the display receive the
signal. A relative magnitude of the received signal at each of the
sensors can then be used to interpolate the position of the stylus
tip. In electrostatic technologies, an electrostatic field is
generated at the tip of the stylus which is detectable by a
self-capacitance touchscreen, as if the stylus tip was larger than
it actually is. In effect, the electrostatic field is used to
magnify the effective size of the stylus tip as detected by the
self-capacitance sensing touchscreen system.
[0007] In order to meet the performance requirements demanded by
many recent latest applications, touchscreens are rapidly migrating
to mutual capacitance sensing--or a combination of self and mutual
capacitance sensing.
[0008] Some conventional tether-free styluses have used a magnetic
antenna for the synchronization signal for a host-to-stylus
transmission. Synchronization is done by using a 13.56 MHz
amplitude shift keying (ASK) signal. Two antennas are used. A
transmitter antenna is implemented as 1+3 turns coil, embedded in
an indium tin oxide (ITO) portion of a touch screen panel routed at
the host side. A receiver antenna is a coil placed inside the
stylus. A drawback to such a conventional approach can be the high
cost and complicated mechanical construction of the transmitter
antenna.
[0009] Another type of stylus is a self-synchronized active stylus
(SSAS). An SSAS can generate a square wave signal on a stylus tip.
The signal waveform phase and frequency are not synchronized with
the host. A host touch screen controller can receive the square
wave signal and calculate a stylus touch position based upon the
signal. One conventional SSAS system will now be described with
reference to FIGS. 21A and 21B.
[0010] FIG. 21A shows a host end of a system 2100. A sense (ITO)
panel 2101 can be connected to a selective receiver 2103. A sense
panel 2101 can include a number of receive lines. Selective
receiver 2103 can detect the panel receive line(s) with the maximum
received signal to determine a stylus position. A detected stylus
signal can also include force data which can be decoded by decoder
2105. A host CPU 2107 can provide force and position (Touch Signal)
data for an application run by the host device 2109.
[0011] FIG. 21B is a block diagram of a conventional SSAS 2111.
Conventional SSAS 2111 is an "active" stylus, and thus generates a
signal for transmission to sense panel. A reference clock 2119 can
generate signal that can be amplified by amplifier 2121 and driven
on a stylus tip 2123, and thereby supplied to a host sense (i.e.,
ITO) panel. A stylus 2111 can also include a force sensor 2113 to
detect the force at the stylus tip 2123 that is measured by
measurer 2115. Force data are transmitted by modulating the carrier
frequency with a modulator 2117. The signal transmitted by the
stylus 2111 can induce a signal in the sense panel 2101 of the host
system 2100, for subsequent decoding. Stylus 2111 can be powered by
from a battery.
[0012] A drawback to a conventional SSAS like that of FIG. 21B can
be limited life due to power consumption.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1A to 1C are a sequence of diagrams showing a human
interface device (HID) and operations according to an
embodiment.
[0014] FIG. 2 is a block diagram of a HID according to an
embodiment.
[0015] FIG. 3 is a state diagram showing power states of a HID
according to an embodiment.
[0016] FIG. 4 is a partial side cross sectional view of a stylus
device according to an embodiment.
[0017] FIG. 5 is a side view of a stylus device according to
another embodiment.
[0018] FIG. 6 is a side view of a stylus device according to a
further embodiment.
[0019] FIG. 7 is a state diagram showing main operations of a HID
according to an embodiment.
[0020] FIG. 8 is a state diagram showing power states of a HID
according to an embodiment.
[0021] FIG. 9 is a state diagram showing dynamic tip voltage
control for a HID according to an embodiment.
[0022] FIG. 10 is a diagram showing proximity sensing that can be
included in embodiments.
[0023] FIGS. 11A to 11C are diagrams showing a proximity sense
circuit and operations according to embodiments.
[0024] FIG. 12 is a flow diagram showing a proximity sensing
operation for a circuit like that of FIG. 11A.
[0025] FIGS. 13A and 13B are diagrams showing a proximity sense
circuit and operations according to another embodiment.
[0026] FIG. 14 is a block schematic diagram showing a proximity
sense circuit according to a further embodiment.
[0027] FIG. 15 is a diagram showing control circuit functions of a
HID according to an embodiment.
[0028] FIG. 16 is state diagram showing operations of a processing
section of an HID according to an embodiment.
[0029] FIG. 17 is state diagram showing power control operations of
a HID according to an embodiment.
[0030] FIG. 18 is a flow diagram of a sleep timer interrupt service
routine (ISR) that can be included in embodiments.
[0031] FIG. 19 is a flow diagram of an input ISR that can be
included in embodiment.
[0032] FIG. 20 is a block schematic diagram of HID according to one
particular embodiment.
[0033] FIGS. 21A and 21B are block diagrams showing a conventional
self-synchronized active stylus (SSAS) system.
DETAILED DESCRIPTION
[0034] Various embodiments will now be described that show human
interface device (e.g., stylus) having a position indicating part
(e.g., tip), in which the device can switch between a low power and
active mode based upon whether the device is handled or touched by
the human body. By utilizing a low power mode, power consumption
can be reduced.
[0035] According to some embodiments, a body of the device can be
used as a capacitance sense electrode to detect the proximity of a
human body part (e.g., hand). Upon detection of a body part, the
device can switch to an active mode, and transmit a position signal
from a position indicating end (e.g., tip). Further, once the
position indicating end comes in contact with a sensing area (e.g.,
host sense surface), a position signal amplitude can be
reduced.
[0036] In some embodiments, the device can be a stylus having a
sense electrode on an outer surface for sensing the grasp of a
human hand. In a particular embodiment, a stylus body and tip can
be a contiguous structure, formed of metal (or another conductive
material), and serve as the sense electrode. In other embodiments,
a stylus can include a nonconductive body surrounded by a
conductive material (e.g., a conductive polymer or the like) which
serves as the sense electrode.
[0037] Referring to FIGS. 1A to 1C, a human interface device 100
according to an embodiment is shown in a series of diagrams. Device
100 can be a stylus that includes a sense electrode 102, a position
indication part (hereinafter "tip") 104, and a control electronics
106. In the particular embodiment shown, device 100 can also
include a shield electrode 138. A sense electrode 102 can form all,
or part, of a body of the device 100. Alternatively, a sense
electrode 102 can be formed on the device. In some embodiments, the
sense electrode 102 can form an outer surface of the device 100,
and a human body can come into direct contact with the sense
electrode 102. However, in other embodiments, a device 100 can
include an insulating layer formed on the sense electrode 102, and
a human body part does not directly contact the sense electrode
102. In some embodiments, a sense electrode 102 can be formed on an
inner surface of the body. A sense electrode 102 can be formed of
any suitable conductive material, including but not limited to: a
metal (including an alloy) or a conductive polymer. A sense
electrode 102 can be positioned on and/or cover a sufficient outer
area of the device 100 to detect when it is handled by a user.
[0038] A tip 104 can indicate a position when used in conjunction
with a host device sense array (not shown), and can be formed of a
conductive material. In some embodiments, a tip can be part of a
conductive body that also includes the sense electrode. For
example, a stylus body can be a contiguous metal structure that is
hollow and comes to a point at the tip 104. In other embodiments, a
tip 104 can be a separate structure from the sense electrode 102. A
tip 104 can also include a force sensor to determine when the tip
comes into contact with a surface, including the amount force
applied. A shield electrode 138 can be formed proximate the tip,
and be composed of a conductive material. A shield electrode and
tip can be separate structures, or parts of the same unitary
structure. Similarly, a shield electrode and a sense electrode can
be separate structures, or parts of the same unitary structure.
[0039] Control electronics 106 can include circuits for switching
the device 100 between low power and active modes based on a
capacitance sensing with the sense electrode 102. Control
electronics 106 can also include a power source for powering such
circuits. In some embodiments, all of the control electronics,
including a power source, can be formed within the body of the
device 100. In such embodiments, the stylus can be considered
"untethered". Particular circuits of the control electronics 106
will be described in more detail below.
[0040] FIG. 1A shows a device 100 in a low power mode. In a low
power mode, control electronics 106 can drive sense electrode 102
with a sense signal (Sense), and monitor a capacitance of sense
electrode 102 via monitor path 112. In particular embodiments, a
sense signal can be a time varying signal, and control electronics
106 can include an integrator circuit for determining a capacitance
at sense electrode 102 based on the sense signal (Sense). A device
100 can be in a low power mode in any of the following states: upon
power up, when not being handled, or after a certain amount of
inactivity (timeout condition).
[0041] FIG. 1B shows a device 100 when it is handled, but not in
contact with a host sense array surface. Upon contact by human body
parts 114, a capacitance of sense electrode 102 will change
significantly (i.e., capacitance will increase). Control
electronics 106 can sense the increase via monitor path 112, and in
response, enter an active mode. In an active mode, control
electronics 106 can drive a first position signal (Pos(HV)) at tip
104. Such a signal can be detected (e.g., induce a response) by a
host when in sufficient proximity to a host sense array, to thereby
indicate a position of the device with respect to the host sense
array. In some embodiments, a first position signal (Pos(HV)) can
be a time varying signal. Further, a position signal (Pos(HV)) can
be different than sense signal (Sense). For example, a position
signal (Pos(HV)) can have a higher frequency and/or greater
magnitude than a sense signal (Sense). However, in other
embodiments, a sense signal (Sense) can be the same as a first
position signal (Pos(HV)).
[0042] In the particular embodiment shown, a shield electrode 138
can be driven with the first position signal (Pos(HV)) in the
active mode. As noted above, in other embodiments, shield electrode
can be part of the same structure as the sense electrode, tip, or
both.
[0043] In this way, a device with position indicating tip can
switch from a low power mode to an active mode in response to the
proximity of a body part. In particular embodiments, a stylus can
switch from a low power mode to an active mode in response to being
handled.
[0044] FIG. 1C shows a device 100 when a tip 104 comes into contact
with a surface 110. A surface 110 can be formed over a host sense
array, for example. Contact with surface 110 can be detected by a
force sensor in tip 104 and signaled to control electronics 106. In
response to such contact, a device 100 can be switched to a
contact-active mode. In a contact-active mode, control electronics
106 can drive a second position signal (Pos(LV)) at tip 104. Such a
signal can be a lower power signal than the first position signal
(Pos(HV)). In a particular embodiment, second position signal
(Pos(LV)) can be a lower voltage (lower amplitude) signal than a
first position signal. In addition, in the embodiment shown, in the
contact-active mode, control electronics 106 can connect the shield
electrode 138 to a device ground 113.
[0045] In this way, a device with position indicating tip can
switch from a higher power position signal to a lower power
position signal upon contact with a surface, and ground a shield
electrode.
[0046] Referring now to FIG. 2, a stylus device 200 according to an
embodiment is shown in a block diagram. Stylus 200 can include
items like those of FIGS. 1A-1C, including a sense electrode 202
and tip 204, and control electronics. In the embodiment shown,
control electronics can include a processing section 214 (shown as
CPU, but any suitable processing circuits can be used), clock
source 216, a force sensing circuit 218, a proximity sensing
circuit 220, modulator 222, booster circuit 224, and battery 226.
Stylus 200 also shows buttons 228. Buttons 228 can be one or more
buttons that can be actuated to provide additional input
functionality.
[0047] In some embodiments, a stylus 200 can be a self-synchronized
active stylus (SSAS) that generates an internal, fixed frequency,
filtered, rectangular position signal. Such a signal can be
supplied to tip 204, and modulated to enable data to be included in
the signal. In particular embodiments, a position signal at a tip
204 can create (induce) a current in the electrodes (e.g., indium
tin oxide, ITO, electrodes) in a sense array of a host device (not
shown). Such a current can be received by a controller (not shown),
which can make a stylus tip position determination. A position
signal emitted by a tip 204 may not be synchronized to a receiver
(i.e., host) side by frequency, phase or amplitude.
[0048] Referring still to FIG. 2, a processing section 214 can
perform a number of functions, including but not limited to:
initializing and configuring the stylus 200 upon power on; power
management; preparing force data for transmission in a position
signal and/or varying operations/modes according to force data;
detecting states of button(s) 228, varying operations/modes
according to proximity sense values received from proximity sense
circuit 220, and monitoring a power supply level. Initializing and
configuring stylus 200 can include initializing the stylus 200 into
a low power mode upon power on. Power management functions can
include switching off various circuits according to operational
mode, disabling signals and/or controlling a signal form (i.e.
frequency and/or amplitude). In particular embodiments, power
management functions can include placing stylus 200 into a low
power sleep mode, and waking the stylus from such a mode in
response to particular inputs.
[0049] Proximity sense circuit 220 can utilize a sense electrode
202 to detect the proximity of a human body (e.g., determining when
the stylus is handled). Such proximity sensing results can be used
by processing section 214 for power management functions. For
example, upon sensing a human body, the stylus 200 can switch from
a low power mode to an active mode. In some embodiments, a
proximity sense circuit 220 can always be on, continually detecting
a capacitance at sense electrode 202. In other embodiments,
proximity sense circuit 220 operations can vary according to mode.
For example, in a low power mode, proximity sensing circuit 220 can
consume less power, while in the active mode the circuit can
consume more power. In a very particular embodiment, in a low power
mode, a proximity sense circuit 220 can sense a lower frequency
signal, while in an active mode, a proximity sense circuit 220 can
sense with a higher frequency signal.
[0050] A clock source 216 can provide one or more time varying
signals for use by a stylus 200. For example, a time varying signal
can be applied to sense electrode 202 for capacitance sensing of a
human body. Further, the same, or a different signal, can be
provided to tip 204 as a position signal that induces a response on
a host sensing surface. In one very particular embodiment, a clock
source 216 can provide two square wave signals shifted by 180
degrees from one another. In some embodiments, a clock source 216
can be connected to an oscillation source 230, such as a crystal,
as but one very particular example.
[0051] A force sensing circuit 218 can measure a force applied at
tip 204. A sensed force value can be used for various functions. A
sensed force value can be used to alter a mode of operation of the
device 200 (switch from a low power state to an active state). In
addition or alternatively, a force value can be converted to a
digital value and encoded in a position signal emitted from tip
204. Still further, a force value can be used to dynamically change
an emitted position signal (e.g., change a position signal
magnitude when the tip contacts a surface, or according to
proximity to the surface). In one very particular embodiment, a
force sensing circuit 218 can covert force values into digital
values of 8-12 bits for encoding in a position signal.
[0052] Modulator 222 can modulate a position signal provided to tip
204 to enable such a signal to transmit data to a host device. Such
data can include any suitable data value indicating stylus state
and/or positions. As but a few examples, modulated data can
indicate a sensed force at tip 204, a power state (e.g., battery
bad indication, battery level), a state of any of the button(s), or
a device identification value. Such data can be extracted from the
position signal by a host device for use by an application. In some
embodiments, a modulated signal can be applied to sense electrode
202 as a sense signal.
[0053] Button(s) 228 can include one or more input buttons on the
stylus 200. Such buttons can take any suitable form, including but
not limited to: mechanical buttons or "touch" surface buttons
(i.e., capacitance/resistive sense electrodes different from the
sense electrode 202), for example.
[0054] A battery 226 can provide power to stylus 200. In one
embodiment, battery 226 can fit within a stylus housing, along with
all control electronics. A battery 226 can take any suitable power
source form, including rechargeable or non-rechargeable batteries,
as well as other power storing devices such as
"supercapacitors".
[0055] In the particular embodiment of FIG. 2, stylus 200 can
include booster circuit 224. A booster circuit 224 can increase a
power supply voltage for control electronics as compared to that
provided form battery 226. In one very particular embodiment, a
booster circuit 224 can be programmed to provide output voltages of
1.8 V, 2.7 V or 5 V from a lower voltage (e.g., 1.5 V or lower)
according to the integrated circuits used to implement the control
electronics. In some embodiments, a booster circuit 224 can provide
a dynamic power supply voltage, providing one power supply voltage
in a first mode (e.g., low power mode) and another, higher voltage
in a second mode (e.g., active mode).
[0056] In this way, a stylus according to embodiments herein, can
include various features not present in conventional styluses,
including but not limited to: a sense electrode to sense the
proximity of a hand holding the stylus; active power management
based on detecting the human hand and/or sensed force; dynamic
control of a position signal emitted at a tip; and stylus power
information encoded and transmitted through a position signal to a
host.
[0057] FIG. 3 is a state diagram 300 showing power control
operations of a stylus according to one particular embodiment.
Operations shown in FIG. 3 can be realized by a processing section
included within the control electronics of a stylus, as described
herein, or equivalents. As shown, a stylus can operate a low power
mode 332 and an active mode 334. In a lower power mode 332, a
stylus can draw a power supply current in a first range (I1). In an
active mode 334, a stylus can draw a power supply current in a
second range that is greater than the first range (I2>I1). In a
very particular embodiment, low power current I1 can be in the
range of 7 uA, while active current I2 can be in the range of about
78 uA.
[0058] Upon power-on or reset (POR), a stylus can enter low power
mode 332. In one very particular embodiment, in a low power mode
peripheral circuits (e.g., circuits other than a proximity sensing
circuit and all or portions of a processing section) can be turned
off, and a stylus can execute proximity sensing only (i.e., sleep
until it is handled). In addition or alternatively, in a low power
mode, a booster circuit can provide a minimal power supply
voltage.
[0059] As shown by "Proximity On", upon detecting the proximity of
a human body part (e.g., hand), a stylus can transition from the
low power state 332 to the active state 334. In one very particular
embodiment, in an active mode peripheral circuits can be enabled,
allowing a position signal to be transmitted and other inputs to be
detected (e.g., buttons, tip force, etc.). In addition or
alternatively, in an active mode, a booster circuit can increase a
power supply voltage (as compared to the low power state).
[0060] As shown by "Proximity Off", upon no longer detecting the
proximity of a human body part, stylus can return to the low power
mode.
[0061] According to embodiments, a device can include a sense
electrode having the dual function of a proximity sensor and body
electrode for the device. A sense electrode can have the feature of
being sensitive to fingers, and not sensitive to other objects,
such as metal objects that could be included in a transportation
bag containing the device. According to embodiments, proximity
sensing can discriminate finger touches from other conductive
objects using a surrounding conductive sense electrode on an outer
surface of the device. A difference between fingers and metal can
be a number of touch points. When handled, a stylus can be touched
in multiple locations (e.g., three points) as opposed to a smaller
number of locations (e.g., one or two points), as could happen when
the device is on the table or in bag with other conductive
objects.
[0062] In some embodiments, distinguishing between fingers and
other objects can be based on a sensed capacitance. In addition or
alternatively, distinguishing between fingers and other objects can
be based on a sensed capacitance of multiple sense electrodes on an
outer surface of a device.
[0063] FIG. 4 is partial cross sectional view of a stylus 400
according to another embodiment. A stylus 400 can include a sense
electrode 402, a tip 404, control electronics 406, battery 426,
housing 436, shield portion 438, and protection rings 440. A tip
404 can be a conductive structure with a force sensor. A shield
portion 438 can be a tapering portion between a tip and a handled
portion of the stylus 400. In some embodiments, a tip 404 and
shield portion 438 can be an integral structure. In other
embodiment such structures can be separate electrodes.
[0064] Control electronics 406 can provide the various
functionalities described herein, or equivalents, including
switching between modes based on proximity sensing by sense
electrode 402 and/or force at tip 404. In the embodiment shown,
control electronics 406 can be mounted on a printed circuit board
(PCB) that fits within the housing 436 of the stylus 400. A battery
426 can fit within a housing 436, and is understood to have
connections (not shown) to enable power to be supplied to control
electronics 406.
[0065] A housing 436 can form the shape of the held portion of the
stylus 400, and can have any suitable elongated shape, including
but not limited to, shapes having a circular, oval, square or
triangular cross sectional profiles. A sense electrode 402 can be a
material formed on an outer surface of housing 436. A sense
electrode 402 can be a contiguous structure, completely covering a
portion of housing 436. In addition, a stylus 400 can include more
than one electrode, or portions of same electrode, disposed at
various locations on an outer surface of housing. It is understood
that sense electrode(s) can be disposed on surface housing 436, be
embedded within housing 436, or extend through housing 436 from an
interior of the device 400.
[0066] Protective rings 440 can prevent false triggers of a
proximity sensing operations that can occur when the device is
placed on a conductive surface. As shown, protective rings 440 can
be formed at opposing ends of the stylus to prevent the sense
electrode 402 from contacting a surface. Protective rings 440 can
be formed of an insulating material and/or be electrically
insulated from sense electrode 402.
[0067] In one very particular embodiment, a housing 436 can be
plastic and a sense electrode 402 can be a conductive rubber layer
formed on the housing 436, close to the tip 404. While a sense
electrode of a conductive polymer has been described, as noted
above, any suitable conductive structure can be employed as a sense
electrode, including but not limited to: a spring, metal ring,
metal dots or any other conductive objects that can provide low
impedance connection to the human body.
[0068] FIG. 5 is a side view of a stylus 500 according to another
embodiment. A stylus 500 can include items like those in FIG. 4,
including control electronics and a battery (not shown, but
understood to be within the stylus body). Protective rings 540 can
be included, as in the case of FIG. 4.
[0069] The embodiment of FIG. 5 can differ from that of FIG. 4 in
that a housing 536 can be formed from a contiguous tube formed from
a conductive material, such as a metal. In such an embodiment, any
of a sense electrode 502, shield portion 538, and/or tip 504 can be
part of a same unitary housing 536.
[0070] In an embodiment like that of FIG. 5, a stylus housing
(e.g., case) can serve as both a sense electrode and a structure
for containing control electronics and a power supply (e.g.,
battery). Such an arrangement can be cost effective to manufacture
as it is a single component. Further, such a housing/sense
electrode 502/536 can serve as an electro-magnetic interference
(EMI) shield for components contained within. Accordingly, a stylus
case can be used as proximity sensor and body electrode in the same
time. When a human hand touches the stylus case, a sensed
capacitance can increase many times. Such a large capacitance
change can be detected with low power proximity sense circuits.
[0071] Referring still to FIG. 5, in embodiments having a unitary
body/sense electrode structure, a grounding electrode 542 can be
included. In proximity sensing operations, a grounding electrode
542 can be connected to a device ground to provide a return path
for a proximity sensing current. In a particular embodiment, a
grounding electrode 542 can be a ring shaped structure formed of a
conductive material (e.g., metal) that is insulated from the
housing/sense electrode 502/536.
[0072] FIG. 6 is a side view diagram of a stylus 600 according to a
further embodiment. A stylus 600 can include items like those of
FIG. 4, and such like items are referred by the same reference
character, but with the leading digit being "6" and not "5". Stylus
600 can differ from that of FIG. 5 in that it shows a button 628,
the operation of which can be detected by control electronics (not
shown). Stylus 600 also shows a structure 604'/628' at an end
opposite to tip 604. Such an end can serve as a second tip 604'
and/or another button 628'. In an active mode, a second tip 604'
can emit a position signal that is different from that of tip 604,
and therefore distinguishable by a host (i.e., a host application
can distinguish between tip 604 and second tip 604'). For example,
tip 604 can be a "drawing" tip for an application, while second tip
604' can be a "erasing" (e.g., undo) tip for the application.
[0073] Having described various input devices, including styluses,
methods of operation for such input devices will now be
described.
[0074] FIG. 7 is a diagram showing main functions 700 of a human
input device (HID) having a position indicating tip, according to
one embodiment. Main functions 700 can include a start 702. A start
702 can include power-on and/or reset conditions. Hardware for the
device can be initialized 704. A device can then enter a low power
state 706. In a low power state, all or a portion of those circuit
not used for proximity sensing can be placed into non-operational,
low power modes. A device can then enter a low power state machine
708.
[0075] Upon entering the low power state machine 708 a device can
be in a low power state 710 (i.e., OFF), and can be conceptualized
as "sleeping". However, it is understood that proximity sensing can
be operational to detect the proximity of a human body part (e.g.,
hand). In response to active events 712, a device can enter an
active state (State=Active). Active events 712 can be events
indicating operation of the device, and can include, but are not
limited to: detecting the proximity of a body part (Proximity On);
sensing force at the tip, or the activation of button. In a very
particular embodiment, such events can generate interrupts for a
processing section (e.g., CPU).
[0076] Upon entering the active state, a processing section can
broadcast (714) to circuits the active states. Circuits that are in
low power, or an off state, can turn on or power-up. In an active
mode, a device can provide position indication or other functions.
As but one example, unlike the low power state, a device can emit a
position signal at one or more tips.
[0077] In response to low power events 716, a device can return to
a low power state (State=Low Power). Low power events 716 can
include no longer detecting the proximity of the body part
(Proximity Off) and/or a timeout condition (e.g., lack of any
active inputs for a set period of time).
[0078] FIG. 8 shows a low power state function 800 that can be
included in embodiments. A device can be in a low power state 802.
The state can be monitored 804. If a state is not active (No from
804), a device can remain in a sleep state 806, and return to
monitoring a state. If state is active (Yes from 808), the low
power state can be ended.
[0079] In some embodiments, a low power state function 800 can be
executed by processor circuits in a low power mode. That is,
minimal circuits can be deployed for this function for greatly
reduced power consumption in the low power mode.
[0080] FIG. 9 shows dynamic tip voltage function 900 according to
an embodiment. A function 900 can include measuring a tip force
sensor 902. Such an action can include receiving or retrieving a
force value from a force sensor at a tip. From a force value, a
determination can be made as to whether the tip is pressed on a
surface or not 904. If a tip is pressed (YES from 904), a voltage
level of a position signal emitted at the tip can be set to a low
value. If a tip is not pressed (NO from 904), a voltage level of a
position signal emitted at the tip can be set to a high value.
[0081] Thus, when a device having a position indicating tip is away
from a sense surface, a voltage at the tip can have a high
magnitude, to aid in sensing a position (e.g., enable "hover" and
other operations). However, once a tip is in contact with such a
surface, a position signal voltage can be reduced, to thereby
conserve power.
[0082] Having described various input devices, including styluses,
proximity sensing operation for such devices will now be
described.
[0083] FIG. 10 is a diagram showing an equivalent of a proximity
sensing operation of a device, that can be included in
embodiments.
[0084] A sense electrode/housing 1002/1036 can be driven with a
time varying sense signal (e.g., from clock source 1030). A sense
signal can create a proximity sensor current I.sub.body. Current
I.sub.body can be measured by a virtual current meter of proximity
sense circuit 1012. A high current I.sub.body measure can indicate
the sense electrode is being touched by a hand. A relatively small
I.sub.body current measure can indicate that the proximity sensor
is not touched.
[0085] Current I.sub.body can flow from a clock source 1030 through
a sense electrode 1002 to the human body 1014, and back to the
clock source 1030 via a capacitance C.sub.ST. Thus, a capacitance
C.sub.ST and the human body impedances can be the parameters that
define the value of current I.sub.body. In the particular
embodiment shown, a sense signal from clock source 1030 can be the
same for the sense electrode and body of a device.
[0086] A capacitance C.sub.ST can vary based on how many conductive
objects connected to a device ground 1013 are close to the sense
electrode 1002. In embodiments where a device body and sense
electrode are a single metal piece (e.g., solid metal pipe, or
similar), the proximity sense circuit 1012 can be can be shielded
from a device ground 1013. In such a case, C.sub.ST can be small,
and therefore I.sub.body is also small and the proximity of an
object (e.g., hand) may not be detected. To address such a problem,
embodiments can include a grounding electrode (e.g., 542 in FIG. 5)
on a device body to create a path for I.sub.body current and give
rise to high C.sub.ST values. Accordingly, inclusion of a grounding
electrode can increase reliability of such proximity sensing.
[0087] It is noted that in an embodiment like that of FIG. 4 (i.e.,
housing of non-conductive material) can exclude a grounding
electrode noted above. A human hand can have a high capacitive
coupling to control electronics (including a proximity sense
circuit) within the housing, thus C.sub.ST can be high, and
therefore I.sub.body current can also be high.
[0088] Thus, according to embodiments, a human interface device
having a tip, such as a stylus, can detect the proximity of a hand
by an increase in capacitance at a sense electrode formed on, or
making up, the housing of a device. It is understood that
embodiments can utilize any suitable capacitance sensing techniques
for proximity sensing operations.
[0089] FIG. 11A shows a proximity sense circuit 1100 according to
one particular embodiment. A proximity sense circuit 1100 can
include a sense signal driver 1116, switch network 1148, comparator
1150, and integrating components C.sub.INT/R.sub.INT. A sense
signal driver 1116 can drive sense clock (Sense Clock) to generate
control signals for switch network 1148. By operation of switch
network 1148, a sense signal can be driven on the sense electrode
1102.
[0090] Switch network 1148 can selectively connect sense electrode
1102 to integrating components C.sub.INT/R.sub.INT (via a bus 1152,
in the embodiment shown). Such an operation can integrate a signal
on the sense electrode (as modified by a capacitance C.sub.BODY) to
generate an integrated voltage V.sub.CINT on C.sub.INT. Thus,
V.sub.CINT can represent a measurement of C.sub.BODY, which can
exist between sense electrode 1102 and a body ground 1146.
[0091] Comparator 1150 can compare an integrated voltage
(V.sub.CINT) to a threshold voltage Vth to determine whether or not
the device is in contact with a human body (e.g., is being
handled). In some embodiments, a comparator 1150 can be dynamically
powered for even greater reductions in power consumption. In a low
power mode, a timer circuit can periodically provide power to a
comparator 1150, which can then comparer V.sub.CINT to Vref. If
proximity of a human body is not detected, the comparator 1150 can
be returned to a low power state. In a very particular embodiment,
comparator 1150 can operate with an 8 Hz scan rate, for a low power
consumption rate (i.e., less than one uA operating current).
[0092] In operation, by action of switch network 1148, a sense
electrode 1102 can switch between VDD (via switch SW2) and
integrating capacitor C.sub.INT (via switch SW1). As noted, switch
SW1 can connect sense electrode 1102 to a bus 1152. Switch SW2 can
connect sense electrode to VDD. Switches SW1 and SW2 work in
opposite phases. In some embodiments, integrating capacitor
C.sub.INT can be connected continuously to bus 1152. Thus, a charge
from VDD can be transferred to C.sub.INT through a C.sub.BODY
capacitance. Integrating components C.sub.INT/R.sub.INT can be
connected between bus 1152 and a device ground 1113.
[0093] A comparator 1150 can be a low power comparator that
generates an interrupt (INT) when V.sub.CINT falls below Vref. In
response to such an interrupt, a processing section of the device
(e.g., CPU) can wake up from a low power state, and place
peripheral circuits into a low power mode. A reference voltage Vref
can be generated by application of an existing clock to a low pass
filter (LPF) internal to control electronics, or with a voltage
divider (e.g., external resistive divider), or any other suitable
reference voltage generator.
[0094] In one very particular embodiment, circuit elements within
area 1115 can be part of a same integrated circuit.
[0095] FIGS. 11B and 11C show proximity sensing operations for a
proximity sensing circuit like that of FIG. 11A. When a device
(e.g., stylus) is in a palm, C.sub.BODY can be relatively high and
thus a voltage on C.sub.INT (V.sub.CINT) is also relatively high.
Thus, as shown in FIG. 11B, V.sub.CINT can be greater than Vth. A
comparison operation (e.g., comparator 1150) can detect this
difference, and generate a signal INT to indicate the device is
being handled (i.e., initiate a switch to an active mode).
[0096] Conversely, when a device is not in, or ceases to be in a
palm, C.sub.BODY can be relatively low and thus V.sub.CINT is also
relatively low. Thus, as shown in FIG. 11C, V.sub.CINT can be less
than Vth. A comparison operation can detect this difference, and
provide an indication that the device is not being handled (i.e.,
maintain, or initiate a switch to a low power mode).
[0097] In one very particular embodiment, for a given sense signal
and expected body capacitance (C.sub.BODY), a value for resistor
R.sub.INT and C.sub.INT can be selected to generate a voltage
V.sub.CINT of about 0.3V to 0.4V, in the event the device is being
handled (V.sub.CINT for Proximity On). In the event the device is
not being handled (V.sub.CINT for Proximity Off), V.sub.CINT can be
less than 0.3 V.
[0098] FIG. 12 shows a proximity sense circuit operation for the
circuit of FIG. 11A. Switch SW1 can be off and Switch SW2 can be on
1202. As a result, C.sub.BODY can be charged to, or toward, the VDD
level. Next, switch SW2 can be off and Switch SW1 can be on 1204.
As a result, the charge on C.sub.BODY can be transferred to
C.sub.INT. A voltage on C.sub.INT (V.sub.CINT) can be compared to a
reference level Vth 1206. If a comparator output is not high (i.e.,
V.sub.CINT<Vref) (No from 1208) switches can continue to switch
as in 1202/1204. If a comparator output is high (i.e.,
V.sub.CINT>Vref) (Yes from 1208) a proximity sense can be
triggered 1210 (e.g., "Proximity On").
[0099] In embodiments in which a sense electrode and tip are part
of the same conductive structure (e.g., body, housing), a sense
signal (used for proximity sensing) and position signal (emitted
from the tip) can be the same signal. Consequently, a voltage on
integrating capacitance C.sub.INT can subtract from a voltage on a
sense electrode. Thus, there can be some reduction in a voltage at
a tip, as compared to the driving voltage level. In embodiments
having components as noted above (voltage V.sub.CINT of about 0.3V
to 0.4V in the event the device is being handled), a tip voltage
can be about 0.3 V smaller than without proximity sensing, and can
be asymmetrical. However, such a reduction can represent a 3%
reduction, and so is not anticipated to present a significant
impact on performance.
[0100] FIG. 13A shows a proximity sense circuit 1300 for a HID
according to another embodiment. Proximity sense circuit 1300 can
provide for a low power, small size circuit solution to sensing the
proximity of a hand, or the like. Like the embodiment of FIG. 11A,
proximity sense circuit 1300 can include a switch network 1348, and
utilize integrating components C.sub.INT/R.sub.INT.
[0101] Proximity sense circuit 1300 can differ from that of FIG.
11A in that a switch network 1348 can be controlled by a "low
power" clock (LP Clock) that can be a clock already present in the
control electronics. Such a LP Clock can operate at a relatively
low frequency, such as less than 100 KHz, or less than 50 KHz. In
one very particular embodiment, LP Clock can be a 32 kHz clock.
[0102] Proximity sense circuit 1300 can also differ from that of
FIG. 11A in that it may not include a comparator (e.g., 1150).
Instead, an integrated voltage V.sub.CINT can be applied directly
as an input to processing section. In the embodiment shown,
V.sub.CINT can be applied via a general purpose I/O (GPIO) 1354 of
a system.
[0103] In one very particular implementation of proximity sense
circuit 1300, a LP Clock can be a 32 kHz internal low speed
oscillator that can be used to control a switch network only in a
low power mode for power consumption minimization. As noted above,
a comparator can be replaced by using a GPIO input, for further
reductions in power consumption. In such a particular embodiment, a
GPIO input high level can be about 2V. In embodiments having an
integral sense electrode/tip structure, such an arrangement can
subtract the voltage (e.g., 2V) from a voltage at a tip. However,
this does not adversely affect operations of the device, as the tip
is not used for position indication in the low power (e.g., sleep)
mode. Upon switching to an active mode, proximity sensing can be
based on a lower V.sub.CINT (i.e., as shown in FIG. 11A). R.sub.INT
can be selected to provide stable triggering via GPIO 1354.
[0104] Referring still to FIG. 13A, in particular implementations,
a LP Clock can be subject to some variation, which can adversely
affect the accuracy of proximity sensing. That is, different LP
Clock frequencies can result in different integrated voltage
(V.sub.CINT) levels. To address such variations, a proximity sense
circuit 1300 can include a compensation current digital-to-analog
converter (IDAC) 1356.
[0105] IDAC 1356 can be connected to the bus 1352 shared by GPIO
1354 and switch network 1348. Prior to entering a low power mode,
an IDAC 1356 can undergo a calibration procedure to ensure proper
response for an actual LP Clock frequency. One example of an IDAC
calibration routine for an embodiment like that of FIG. 13A is
shown in FIG. 13B.
[0106] FIG. 13B shows an IDAC calibration 1360 according to an
embodiment. An IDAC calibration 1360 can be performed upon power-on
of a device and/or when switching from an active state to a low
power state. A purpose of IDAC calibration 1360 can be to ensure
that a voltage at C.sub.INT (V.sub.CINT) is below a GPIO input
threshold when the device is not touched.
[0107] A calibration procedure can start from minimal IDAC current
that corresponds to deep, low power state (IDAC=0, 1362). From such
an initial state, an IDAC value (and hence current) can be
increased (IDAC=IDAC+1, 1364) while proximity has not yet been
triggered (NO from 1366). When proximity is triggered (indicating
the GPIO threshold point) (YES from 1366), a coefficient value can
be subtracted from the current IDAC value (IDAC=IDAC-Coefficient,
1368). The coefficient value can establish the hysteresis between
triggering the active and low power states (mode) based on
proximity sensing. In this way, an IDAC response can be tuned to an
actual LP Clock operation, decreasing the sensitivity of the
proximity sense circuit 1300 to variations in a frequency of LP
Clock.
[0108] As in the case of FIG. 11A, in one very particular
embodiment, circuit elements of proximity sense circuit 1300 within
area 1315 can be part of a same integrated circuit.
[0109] FIG. 14 is a blocks schematic diagram of a proximity sense
circuit 1400 according to a further embodiment. Proximity sense
circuit 1400 can combine the features of those circuits shown in
FIGS. 11A and 13A, and like items are referred to by the same
reference character, but with the leading digits being "14" and not
"11" or "13". The embodiment of FIG. 14 can switch between
operations like those of FIG. 11A and those of FIG. 13A. More
particularly, in a low power mode, proximity sense circuit 1400 can
operate like that of FIG. 13A. In an active mode, proximity sense
circuit 1400 can operate like that of FIG. 11A.
[0110] To provide for mode switching, proximity sense circuit 1400
can include switches 1458-0 to 1458-4. More particularly, in a low
power mode, switch 1458-0 can connect a low power clock (LP Clock)
as the signal which can drive a sense electrode 1402 (and tip, in
some embodiments). Such a signal can have a relatively low
frequency, as described in conjunction with FIG. 13A. Switch 1458-1
can be open, isolating comparator 1450 from bus 1452. Switch 1458-2
can be closed, connecting GPIO 1454 to bus 1452. Thus, GPIO 1454
can provide a proximity detection result. Switch 1458-4 can be
closed, so that integration is performed with C.sub.INT and
R.sub.int. Switch 1458-3 can be open, so that R.sub.INT is not
included in an integration operation. That is, a value for
R.sub.int is selected for integration according to signal LP Clock.
Proximity sensing can then occur as described for FIG. 13A.
[0111] Also in the low power mode, comparator 1450 and driver 1416
can be disabled, for further power reduction. Further, IDAC 1456
can be included to compensate for variations in LP Clock, as
described in conjunction with FIG. 13B.
[0112] In an active mode, switch 1458-0 can connect an active sense
signal (Active Sense) as the signal which can drive a sense
electrode 1402 (and tip, in some embodiments). Such a signal can
have a relatively high frequency, as compared to LP Clock. Switch
1458-1 can be closed, connecting comparator 1450 to bus 1452, while
switch 1458-2 can be open, isolating GPIO 1454 from to bus 1452.
Thus, comparator 1450 can provide a proximity sensing result by
comparing the voltage across C.sub.INT to Vth. Switch 1458-4 can be
open and switch 1458-3 can be closed, so that integration is
performed with C.sub.INT and R.sub.INT. That is, R.sub.INT is
selected for integration according to the higher frequency signal
Active Sense. Proximity sensing can then occur as described for
FIGS. 11A to 12.
[0113] Referring still to FIG. 14, a proximity sense circuit 1400
can further include sleep timer 1460. In one embodiment, a sleep
timer 1460 can periodically generate an interrupt that can "wake
up" a processing section (not shown), which can then scan GPIO 1454
to determine if the device is being handled (i.e., GPIO high).
[0114] FIG. 15 shows control circuits 1506 of a HID according to
one particular embodiment. Control circuits 1506 can operate on a
number of received inputs and generate outputs. In the embodiment
shown, the inputs can include: a force sensor value (Force Sensor),
proximity sensing result (Proximity), battery voltage (Battery),
button states (Buttons), and a resonator input (Resonator Input). A
Force Sensor value can be generated in response to a sensed force
at a tip. In the embodiment shown, the value can be an analog value
(e.g., current or voltage). Force sensing can utilize any suitable
technique, including piezoelectric or mechanical sensing, as but
two examples. A proximity sensing result can be a capacitance
sensing result, as described herein or equivalents. Such a result
can be a voltage (e.g., V.sub.CINT) or a signal generated from a
sensing (e.g., interrupt). A battery voltage can be used to detect
a low voltage state, and implement a boosting operation and/or
indication in response to such a state. Buttons can be the state of
buttons on the device, and can take the form of any of those
described herein. A resonator input can establish a periodic signal
from which a sense signal (applied to a sense electrode) and/or
position signal (applied to a tip) can be generated. In some
embodiments a resonator input can be from a crystal based
oscillator circuit.
[0115] In the embodiment shown, the outputs can include: a sense
electrode output and a tip output. A sense electrode output can
drive a sense electrode to enable proximity sensing as described
herein. A tip output can be a position signal that can indicate the
position of a tip on a sensing surface (e.g., host array). As noted
above, in some embodiments, a sense signal and position signal can
be the same. Further, a position signal emitted at a tip can have
data (e.g., force data, battery data) encoded therein.
[0116] As understood from above, a human interface device according
to embodiments herein can include a processing section (e.g., CPU)
for controlling operations of the device. According to embodiments,
a processing section can perform any of the following functions:
initialization upon power-on or reset, handling proximity sense
results; reconfiguring the device between active an low power
modes; measuring force; handling force sensor interrupts; writing
data (e.g., force) data to a modulator (to modulate the position
signal); changing a boost voltage; changing a state of the sense
electrode (e.g., shield); monitoring a battery voltage; and
monitoring button states.
[0117] In a particular embodiment, processing section functions,
except initialization, can be called from interrupt routines. This
can minimize processor active time and power consumption. In
essence, a processing section can be maintained in a low power
(e.g., sleep) mode, wake up upon interrupt, executing the interrupt
routine as fast as possible, and then return to the low power
mode.
[0118] FIG. 16 shows processing section functions 1600 according to
an embodiment. Processing section functions 1600 can be functions
executed by a processing section of an HID, such as stylus, as
described herein. In the embodiment of FIG. 16 it is assumed that
the processing section is a CPU.
[0119] Upon power on, a CPU can execute a chip initialization and
configuration procedure (1602). Afterward, a CPU enters a low power
mode (1604). A Proximity On interrupt (Proximity On), can cause a
transition from low power mode to the active mode. More
particularly, circuits can be re-configured for active mode (1606)
and then the CPU can enter the active mode (1608). Conversely, once
in the active mode, a Proximity Off interrupt (Proximity Off), can
result in circuits being re-configured for low power mode (1610)
and then the CPU can return to the low power mode (1604). Further,
when in the low power mode, in response to a Proximity Sensing
Interrupt, CPU can check a proximity value to determine if
proximity has been sensed.
[0120] As shown in FIG. 16, in response to button actions
(Button(s) Interrupts), the CPU can enter the active mode
(1608).
[0121] In the active mode (1680), in response to a Sleep Timer
Interrupt, a read of a proximity value can be made (1612). If
Proximity On is detected, the CPU can remain in an active mode. If
Proximity Off is detected, the CPU can re-configure to the low
power mode (1610).
[0122] In the active mode, a Force Sensor Interrupt can indicate a
tip of the device has contacted a surface. In response to such an
interrupt, a sense signal (SMP) voltage can be decreased, and a
sense electrode (shield) can be connected to ground (1618). A force
sensor measurement can be made (1620). If the force is maintained,
a CPU can remain in the active mode 1608. If the force sensor
indicates release (i.e., tip no longer in contact with surface),
CPU a sense signal (SMP) voltage can be increased, and a sense
electrode (shield) can be disconnected from ground (1622) and
connected to the tip (or connected to receive the same signal as
the tip). A force sensor measurement can be made (1620) once
again.
[0123] In the active mode 1608, a Modulator Interrupt can indicate
a modulator is ready to receive data for write (i.e., data to be
modulated into the position signal). In response to such an
interrupt, data can be written to the modulator 1614. A counter can
be incremented (1616). If the counter has not reached a limit
(Counter is Not Full), a CPU can return to the active mode (1608).
But if a counter has reached a limit (Counter is Full), a force
sensor measurement can be made (1620).
[0124] In one embodiment, force sensor measurements can be skipped
if a device is in a hover mode (active but tip is not in contact
with a surface).
[0125] FIG. 17 is a state diagram 1700 showing power control
operations of a device according to another embodiment. Operations
shown in FIG. 17 can be realized by a processing section included
within the control electronics of a device, as described herein, or
equivalents.
[0126] A device can have two states: a low power state (1702) and
an active state (1704). Upon power-on or reset, a device can go
into the low power state (1702). If a sense electrode is touched
(Proximity On), the device can switch to the active state (1704).
If the device is released (Proximity Off), the device can return
back to the low power state (1702). If the device is in the active
state for longer than a set period of time, and no tip force or
buttons action occur during this time (Timeout), the state machine
can return to the low power state (1702). Such an action can
utilize a timeout timer. Such a timeout timer can save power if a
user holds the device over a long period of time without action
(e.g., falls asleep with the stylus in hand).
[0127] In one particular embodiment, after entering the low power
state from a timeout condition (Timeout), a device cannot enter the
active state via proximity sensing. Thus, in the embodiment shown,
if the low power state is entered due to Timeout, the device can
enter the state only from button actions (Buttons) or a force
sensed at the tip (Force).
[0128] In addition or alternatively, if a device is a low power
state not due to a timeout condition, a device can transition to an
active state only upon proximity sensing (Proximity On) (i.e., not
in response to button or tip action, without proximity). Thus, in
in such a low power state, and button or tip action occurs, a
device can initiate low power proximity sensing.
[0129] As was shown in FIG. 16, embodiments can operate according
to a sleep timer interrupt. A sleep timer interrupt service routine
(ISR) 1800, according to one embodiment, is shown in FIG. 18.
[0130] A sleep timer ISR 1800 can occur periodically with a sleep
timer interrupt (1802). In one particular embodiment, such a
routine can be performed once a second. At the beginning of the
routine a timer (e.g., watchdog timer) can be reset. A device can
determine if a timeout condition has occurred (1804). If a timeout
condition has occurred (Yes from 1804), the routine returns to main
operations (1834).
[0131] If a timeout condition has not occurred (No from 1804), a
proximity sensing operation can be executed (e.g., a sense
electrode can be sensed) (1806). If no proximity is detected (No
from 1808), a lower power state can be entered (1810), and the
routine can return to main operations (1834). If proximity is
detected (e.g., the device is being handled) (Yes from 1808), it
can be determined if the state is active (1812). If the state is
not active (No from 1808), a state can be set to the low power
state (1814), a timeout value can be reset (1816), and the routine
can return to main operations (1834).
[0132] If a state is active (Yes from 1812), a device can decrease
a timeout value (1818) and determine if timeout has occurred
(1820). If timeout has not occurred (No from 1820), a booster
voltage level can be checked (1826). If timeout has occurred (Yes
from 1820), a state can be set to low power (1822), and a force
sensor (and/or buttons) can be configured as an interrupt source
(1824). Thus, a touch (proximity sensing) will not wake the device,
as it has timed out while being held. A routine can then proceed to
a booster voltage level checked (1826).
[0133] If a booster voltage level is not high (No from 1826), the
routine can return to main operations (1834). If the booster
voltage level is high (Yes from 1826), a battery voltage may or may
not be measured based on a battery timer. That is, while a sleep
timer ISR 1800 can occur with some frequency (e.g., once a second),
a battery measurement can be made with less frequency. In the
embodiment of FIG. 18, if a battery counter has not counted down
(No from 1830), the routine can return to main operations (1834)
without making a battery measurement. However, if a battery counter
has counted down (Yes from 1830), a battery voltage measurement can
be made (and the battery counter reset), and the routine can return
to main operations (1834).
[0134] FIG. 19 shows a GPIO interrupt service routine 1900, which
can service button actions of a device. In the particular
embodiment shown, force interrupts (i.e., force detected at a tip)
can occur on a timeout basis only. Upon a GPIO interrupt (1902)
button states can be scanned (1904) to acquire data to send. If a
timeout condition has not occurred (No from 1906), the data to be
sent can be updated with the latest button(s) state, and the
routine can return to main operations (1922).
[0135] If a timeout condition has occurred (Yes from 1906), a
proximity scan operation can occur (1908). If a proximity sensor
(e.g., sense electrode) is not active (No from 1910), a state can
be set to low power (1912), and a timeout value can be reset
(1916). If a proximity sensor is active (Yes from 1910), a state
can be set to active (1914), and force as an interrupt can be
disabled (1918). Data to be sent can be updated with the latest
button(s) state, and routine returns to main operations (1922).
[0136] FIG. 20 shows a human interface device 2000 according to an
embodiment. In one particular embodiment, a device 2000 can be a
SSAS. The control electronics 2015 include a proximity sense
circuit like that of FIG. 14, and like items are referred to by the
same reference character but with the leading digits being "20"
instead of "14".
[0137] Accordingly, in a low power mode, control electronics 2015
can provide low power proximity sensing via a GPIO 2054 and low
power clock (LP Clock) applied via switch 2058-0, while in an
active mode, proximity sensing can be provided via comparator 2050
and a higher frequency (and possibly modulated) sense signal
applied via driver 2016. The embodiment of FIG. 20 also shares bus
2052 with a force sensing circuit, and so includes switch 2058-8
that can isolate IDAC 2056 from the bus when force sensing is
taking place. Further, a reference voltage Vth, used by comparator
2050 in the active mode, can be generated by switch 2058-11
connecting VDD to voltage divider/filter formed by C.sub.filt,
R.sub.ref1, and R.sub.ref2. This ratiometric approach can provide
an accurate reference voltage despite variations in power
supply.
[0138] Various portions of the control electronics 2000 will now be
described according to functional groups.
[0139] A booster circuit 2024 can generate a DC supply voltage VDD
from a lower voltage power source. In the embodiment shown, a
booster circuit 2024 includes switching capacitor CSMP, battery
2023, inductor L200, diode D200, power supply capacitor Cp, control
circuit 2062, and switch 2058-12. A CPU Core 2104 can provide a
voltage control signal Volt.Ctrl to a switching circuit 2062.
Switching circuit 2062 can control a rate at which switch 2058-12
operates to establish the level of VDD. It is understood that other
embodiments can include other types of booster circuits, or
alternatively, no booster circuit if the other components can
operate at the voltage supplied from a power source (e.g.,
battery).
[0140] A button section 2070 can include switch 2058-6, buttons
2028, resistors R200/R201, and GPIOs 2060, 2061. Switch 2058-6 can
enable buttons 2070 by providing power thereto. By way of GPIOs
2060/2061, buttons 2028 can generate interrupts Bint1/Bint2 to CPU
core 2014. It is understood that other embodiments can include
other types of buttons different from mechanical buttons, such as
capacitance sense buttons, as but one example.
[0141] A shield control section can include switch 2058-5, for
dynamic switching of a shield 2038. In one embodiment, in one mode
(e.g., active hover), switch 2058-5 can enable shield 2038 to be
driven by a sense signal. In another mode (e.g., active tip in
contact with surface), a shield 2038 can be connected to a device
ground. Alternate embodiment can include no shield switching.
[0142] A CPU Core 2014 can control operations of a device 2000. In
the embodiment shown, a CPU core 2014 can receive as inputs, a
boosted power supply voltage (VDD), a proximity read input
(received from a comparator 2050 proximity sense circuit), button
interrupts (Bint1, Bint2), a battery monitor (BatMon), a low power
proximity sense interrupt (LP INT) from GPIO 2054, a data ready
interrupt (D INT), a force interrupt (Force INT), a sleep interrupt
(S INT), and force data (Force Data). A CPU Core 2014 can output a
button control (But) (to enable button operations), a low power
mode control (LP), a force read mode signal (Force), comparator
power control (CP), shield control signal (SH), and data to send
(Data to Send). CPU core 2014 represents but one type or processing
section. Alternate embodiments can include application specific
logic, programmable logic, or combinations thereof.
[0143] A clock source 2024 can include crystal based resonator
circuit that includes crystal Q200, capacitors C200/C202, resistor
R208, and driver 2076. A periodic signal TX can be generated having
a frequency based on the selected components. It is understood that
other embodiments can include any other suitable clock source
circuit.
[0144] A device 2000 can include force sensing at a tip location.
In the embodiment shown, force sensing can be based on a variation
in resistance R.sub.force, resulting from force at a tip 2004.
Further, device 2000 can convert an analog value of force into a
digital value, which can then be encoded into a position signal
transmitted at a tip.
[0145] When force sensing is enabled, switch 2058-10 can connect
VDD to a voltage divider R.sub.load/R.sub.force. Thus, changes in
force (R.sub.force) can result in changes in a force measurement
voltage Uforce. A force interrupt (Force INT) can be generated by
detecting a change in Uforce at GPIO 2078.
[0146] In addition, a voltage Uforce can be connected to bus 2053
by switch 2058-9, as an analog input voltage representing a force
value. Comparator 2074 can operate in conjunction with successive
approximation (SAR) circuit 2072, to generate a digital value
representing a detected force (Force Data). In more detail, a
reference voltage Vbg at comparator 2074 can be varied in a
sequence of compare operations, to arrive at a digital value. It is
understood that other embodiments can utilize any other suitable
analog-to-digital conversion to arrive at a digital force
value.
[0147] CPU Core 2014 can receive Force Data, and format it for an
appropriate modulation technique and/or communication protocol, and
output such data values as Data to Send. It is understood that Data
to Send can include data in addition to force data, such as status
data of the device (e.g., battery level, device ID information,
button state, etc.).
[0148] As noted above, a device 2000 can modulate a position signal
emitted at a tip 2004 to enable the transmission of data to a host
device. In the particular embodiment of FIG. 20, modulation
circuits can include shift register (SR) circuit 2068, clock
divider 2066, and modulator 2071. Data to Send can be received by
SR circuit 2068, which can output such data, bit by bit, based on a
divided version of signal TX. A logical XORing of TX with the
output from SR circuit 2068 can result in the modulation of the TX
signal, which can be output as an active mode position signal,
which can selectively be driven at a shield 2038, tip 2004, and
control proximity sensing via switch group 2048.
[0149] FIG. 20 also includes a clock circuit 2064, which can
receive an existing clock signal of the device (Clock Source), and
generate therefrom the low power clock (LP Clock).
[0150] In one embodiment, all circuits within section 2015 can be
part of the same integrated circuit, for an advantageously compact
design for inclusion in the housing for the device. More
particularly, such a compact form is advantageous for maintaining a
slim stylus design. In one very particular embodiment, section 2015
can be implemented with a PSoC.RTM. Programmable System-on-Chip
device, manufactured by Cypress Semiconductor Corporation, having
offices in San Jose, Calif., U.S.A.
[0151] In an alternate embodiment, a reference voltage Vref for
active mode proximity sensing can be formed by a clock divider
circuit having pulse width modulation (PWM) and an internal low
pass filter (LPF) block. A value of Vref can be adjusted according
to the PWM of the signal applied to the LPF block. However, such an
approach can introduce undesirable rippling in a power supply
voltage, particularly when lower frequency clocks (i.e., kHz) are
used.
[0152] In some embodiments, a voltage of battery 2024 can be
monitored, and a resulting battery level can be stored as a value
in a register readable by CPU Core 2014. When a battery voltage
falls to some low level, a booster circuit 2024 may not be able to
boost the voltage to a desired level. For example, if battery 2023
is a 1.5V battery and VDD is about 5V, once the battery falls below
1V, booster circuit 2024 may no longer be able to achieve the 5V
level. When a booster circuit 2024 cannot achieve a desired level,
a "low battery" bit can be set. This bit can be read in proximity
scan procedure. In some embodiments, such a bit can be modulated
into a sense signal to enable a host device to indicate a battery
is low. In addition or alternatively, a local low battery
indication can be provided on the device itself (e.g., visual or
audio indication).
[0153] Embodiments as described herein can provide one or more
power management features for conserving power in a human interface
device, such as a stylus. In particular embodiments, a position
signal emitted at a tip can be turned on/off and/or the
magnitude/frequency of such a signal can be varied according to
mode of operation. This is in sharp contrast to conventional
styluses that have an "always on" tip signal.
[0154] Embodiments can include proximity sensing at locations where
the device is handled. This can enable low power modes when the
device is not being used and/or switching to low power modes after
a period of inactivity. This is contrast to conventional styluses
that are simply turned on or off.
[0155] Embodiments of the invention can encode power status data
into a position signal emitted from a tip. For example, a battery
level indication can be emitted, enabling a host device to let a
use know that battery replacement (or a recharge operation) should
take place in the near future.
[0156] It should be appreciated that reference throughout this
specification to "one embodiment" or "an embodiment" means that a
particular feature, structure or characteristic described in
connection with the embodiment is included in at least one
embodiment of the present invention. Therefore, it is emphasized
and should be appreciated that two or more references to "an
embodiment" or "one embodiment" or "an alternative embodiment" in
various portions of this specification are not necessarily all
referring to the same embodiment. Furthermore, the particular
features, structures or characteristics may be combined as suitable
in one or more embodiments of the invention.
[0157] Similarly, it should be appreciated that in the foregoing
description of exemplary embodiments of the invention, various
features of the invention are sometimes grouped together in a
single embodiment, figure, or description thereof for the purpose
of streamlining the disclosure aiding in the understanding of one
or more of the various inventive aspects. This method of
disclosure, however, is not to be interpreted as reflecting an
intention that the claims require more features than are expressly
recited in each claim. Rather, inventive aspects lie in less than
all features of a single foregoing disclosed embodiment. Thus, the
claims following the detailed description are hereby expressly
incorporated into this detailed description, with each claim
standing on its own as a separate embodiment of this invention.
* * * * *