EP1805587A1

EP1805587A1 - Raw data track pad device and system

Info

Publication number: EP1805587A1
Application number: EP05796332A
Authority: EP
Inventors: Benjamin Lyon; Stephanie Cinereski; Chad Bronstein; Steven P. Hotelling
Original assignee: Apple Computer Inc
Current assignee: Apple Inc
Priority date: 2004-09-24
Filing date: 2005-09-15
Publication date: 2007-07-11
Also published as: CN101027631B; CN101027631A; WO2006036607A1; JP2008515052A

Abstract

An input device and system are described that acquires (measures) raw track pad sensor data and transmits this data to a host computer where it is analyzed by an application executing on one or more host computer central processing units. The resulting input processing architecture provides a track pad input device that is both lower in cost to manufacture and more flexible than prior art track pad input devices. Lower costs may be realized by eliminating the prior art's dedicated track pad hardware for processing sensor data (e.g., a processor and associated firmware memory). Increased flexibility may be realized by providing feature set functionality via software that executes on the host computer. In this architecture, track pad functionality may be modified, updated and enhanced through software upgrade procedures.

Description

RAW DATA TRACK PAD DEVICE AND SYSTEM

Background

[0001] The invention relates generally to computer input devices and more

particularly to a track pad input device that generates and transmits measured (raw)

sensor data to a host computer system. Software executing on the host computer

system analyzes the raw sensor data to determine the user's action.

[0002] A track pad is a touch-sensing planar digitizer input device used

instead of, or in conjunction with, a mouse or trackball. During use, an operator

places a finger on the track pad and moves the finger along the touch-sensing

planar surface. The track pad detects the movement of the finger and in response

provides location and/or motion signals to a computer. There are two common types

of track pad sensor devices: resistive and capacitive. A resistive track pad sensor is a

mechanical sensor that uses two layers of material that are typically separated by

air. Pressure from a finger pushes the top layer (generally a thin, clear polyester

film) so that it touches the bottom layer (generally glass). The voltage at the contact

point is measured and the finger's location and/or motion is computed and

transmitted to a host computer system. After the finger is removed, the top layer

"bounces back" to its original configuration. A capacitive track or touch pad sensor,

in contrast, is a solid-state sensor made using printed circuit board ("PCB") or flex

circuit technology. A finger on, or in close proximity to, a top grid of conductive

traces changes the capacitive coupling between adjacent traces or the self-

capacitance of each trace. This change in capacitance is measured and the finger's

location and/or motion is computed and transmitted to a host computer system. [0003] Referring to FIG. 1, prior art computer system 100 includes track pad

device 105 coupled to host computer module 110 via communication path 115.

Track pad device 105 comprises sensor 120, data acquisition circuit 125, processor

130, memory 135 and transmit circuit 140. In the case of a capacitive track pad

device, as a user's finger(s) is (are) moved over the surface of sensor 120, data

acquisition circuit 125 measures changes in the capacitive coupling between

adjacent sensor elements (or the self-capacitance of a given sensor element).

Processor 130, in conjunction with memory 135, processes the acquired

capacitance signals to compute a signal indicating the user's finger position on

sensor 120 (e.g., a Δx and Δy signal). In some prior art track pad devices, processor

130 may also determine if multiple fingers are activating sensor 120 and whether

certain predetermined finger motions (often referred to as "gestures") are being

made - e.g., "select," "drag," "file open" and "file close" operations. At specified

intervals (e.g., 50 times per second), the user's finger location and/or motion as

determined by processor 130 is transmitted to host computer module 110 via

communication path 115. At host computer module 110, receive circuit 145

receives the transmitted track pad signal and passes it's information to driver

application 150. Driver application 150, in turn, makes the computed sensor

information available to other applications such as, for example, window display

subsystem application 155. Thus, prior art system 100 utilizes a dedicated

processor for measuring and analyzing raw track pad sensor data to generate a

signal that indicates a user's action. [0004] One of ordinary skill in the art will recognize that processor 130 may

be embodied in a general purpose processor (e.g., a microprocessor), a

microcontroller or a special purpose or custom designed processor or state machine

(e.g., an application specific integrated circuit or a custom designed gate array

device). Further, memory 135 is typically used to provide permanent storage for

instructions (i.e., firmware) to drive processor 130 and may, optionally, include

random access memory and/or register storage. A benefit of the architecture of FIG.

1 is that host computer module 110 does not need to know about or understand the

type of data generated by sensor 120. A corollary of this feature is that host

computer module 110 does not process track pad sensor data.

[0005] It will also be recognized by one of ordinary skill that a drawback to

the architecture of FIG. 1 is that the feature set (i.e., what motions are detectable)

provided by track pad device 105 is essentially fixed by its dedicated hardware —

processor 130 and associated firmware (memory 135). Another drawback to the

architecture of FIG. 1 is that each manufactured device 105 includes the cost of

processor 130 and associated firmware memory 135. Thus, it would be beneficial to

provide a track pad device that overcomes these inherent drawbacks.

Summary

[0006] In one embodiment the invention provides a track pad input device

that includes a track pad sensor element that generates output signals representing

a track pad sensor characteristic (i.e., capacitance or resistance), a data acquisition

circuit that measures a (digital) value encoding the track pad sensor's characteristic

and a communication circuit that transmits the measured track pad sensor values to a general purpose processor for analysis, the general purpose processor is also

responsible for executing user and other system level tasks or applications. In one

specific embodiment, the track pad sensor is a capacitive track pad sensor so that

measured values comprise raw track pad sensor values and the general purpose

processor corresponds to a host computer system's central processing unit.

Brief Description of the Drawings

[0007] Figure 1 shows, in block diagram form, a track pad-computer system

architecture in accordance with the prior art.

[0008] Figure 2 shows, in block diagram form, a track pad-computer system

architecture in accordance with one embodiment of the invention.

[0009] Figure 3 shows, in block diagram form, a track pad device and host

computer system in accordance with one embodiment of the invention.

[0010] Figure 4 shows, in block diagram form, a track pad sensor data

acquisition system in accordance with one embodiment of the invention.

[0011] Figure 5 shows, in flowchart form, a data acquisition method in

accordance with one embodiment of the invention.

Detailed Description

[0012] Referring first to FIG. 2, the general architecture of a system

incorporating a track pad device in accordance with the invention is illustrated. As

shown, system 200 includes track pad device 205 coupled to host module 210

through communication path 215. Track pad device 205 comprises track pad sensor

220 that generates signals based on user manipulation thereof, data acquisition circuit 225 for capturing or measuring the sensor's and transmit circuit 230 for

aggregating and periodically transmitting the measured sensor data values to host

module 210 via communication path 215. At host module 210, receive circuit 235

receives the measured sensor data and passes them to driver application 240.

Driver application 240, in turn, processes or analyzes the measured data to

determine the user's conduct (e.g., a "single click," "double click," "scroll" or "drag"

operation), passing the calculated location and/or movement information to other

applications such as, for example, window display subsystem application 245. In

accordance with the invention, driver application 240 is executed by host processor

250 which, as shown, is also responsible for executing (at least in part) one or more

user applications or processes 255. It is significant to note that track pad device

205 has no capability to process or analyze data signals (values) acquired from

sensor 220. In accordance with the invention, sensor data is analyzed by a host

computer system's general purpose processor or central processing unit ("CPU").

[0013] The architecture of FIG. 2 recognizes and takes unique advantage of

the processing power of modern CPUs incorporated in host computer systems (e.g.,

notebook or other personal computers, workstations and servers). This recognition

and the architecture of FIG. 2 permits a computer system 200 that is both lower in

cost to manufacture and more flexible than the systems provided by the prior art.

Lower costs may be realized by eliminating the prior art's dedicated hardware for

processing track pad sensor data (i.e., a processor and associated firmware memory

- see components 130 and 135 in FIG. 1). Increased flexibility may be realized by

providing feature set functionality via software that executes on the host computer's CPU - that is, processing/analyzing measured track pad sensor data on one or more

of the host computer's CPUs. In this architecture, track pad functionality may be

modified, updated and enhanced through conventional software upgrade

procedures.

[0014] The following description is presented to enable any person skilled in

the art to make and use the invention as claimed and is provided in the context of

the particular examples discussed below, variations of which will be readily apparent

to those skilled in the art. Accordingly, the claims appended hereto are not intended

to be limited by the disclosed embodiments, but are to be accorded their widest

scope consistent with the principles and features disclosed herein.

[0015] Referring to FIG. 3, track pad device 300 in accordance with one

embodiment of the invention comprises /ττ-row by /7-column capacitive sensor array

305, data acquisition circuit 310 (itself comprising multiplexer CMUX") circuit 315,

storage capacitor 320 and scan circuit 325) and Universal Serial Bus ("USB")

transmit circuit 330. During operation, MUX circuit 315 is responsible for coupling

and stimulating successive sensor array elements (e.g., rows, columns, or individual

pixels - that is, an element at the intersection of a row and column) to storage

capacitor 320 in a controlled/sequenced manner and indicating that a measurement

cycle has begun to scan circuit 325. When the charge on storage capacitor 320

reaches a specified value or threshold, scan circuit 325 records the time required to

charge storage capacitor 320 to the specified threshold. Accordingly, scan circuit

325 provides a digital value that is a direct indication of the selected sensor array

element's capacitance. USB transmit circuit 330 is responsible for aggregating the measured capacitance values into packets and transmitting them in accordance with

the USB protocol to host module 335 via USB bus 340. One of ordinary skill in the

art will understand that depending upon the version of USB used and the bandwidth

of bus 340, USB transmit circuit 330 may transfer each frame of data to host

module 335 in more than one, one or more than one packet. When the host

module's USB receive circuit 345 receives the measured sensor data from track pad

device 300 via USB bus 340, it unpacks and passes the measured capacitance data

to driver application 350. Driver application 350, in turn, accepts and processes the

raw (measured) capacitance data to provide meaningful cursor movement input to

operating system application 355. (One of ordinary skill in the art will recognize that

scan circuit 325 measures capacitance values from sensor array 305 in a

predetermined order or sequence and that this sequence must be known by driver

application 350 a priori or conveyed to driver application 350 along with the

measured sensor data.) In one embodiment, driver application 350 implements

track pad algorithms traditionally provided by a dedicated track pad processor such

as, for example, processor 130 and firmware memory 135 of FIG. 1.

[0016] Referring to FIG. 4, a more detailed view of MUX circuit 315 as it can

be implemented for a row and column addressable capacitive sensor array is

illustrated. As shown, each row in sensor array 400 is electrically coupled to voltage

source Vcc 405 through MUX-I 410 and to storage capacitor 415 through MUX-2

420. (While not shown in detail, each column of sensor array 400 is similarly

coupled to Vcc 405 and to storage capacitor 415 through other MUX circuits - block

425.) [0017] Referring now to FIG. 5, in operation MUX-I 410 couples a first sensor

array row to Vcc 405 for a specified period of time (block 500) and then isolates or

disconnects that row from Vcc 405 (block 505). Next, MUX-2 420 couples the same

row to storage capacitor 415 for a specified period of time, or until the voltage on

storage capacitor 415 reaches a specified threshold (block 510). If, during the time

MUX-2 420 couples the selected sensor row to storage capacitor 415 the storage

capacitor's voltage reaches a specified threshold (the "Yes" prong of block 515), the

digital value corresponding to the time it took to charge storage capacitor 415 to

the threshold is recorded by scan circuit 325 (block 520). If, during the time MUX-2

420 couples the selected sensor row to storage capacitor 415 the storage

capacitor's voltage does not reach the specified threshold (the "No" prong of block

515), the acts of block 500-510 are repeated. Once a digital value corresponding

to the capacitance of the selected row has been obtained (block 520), a check is

made to see if there are additional rows in sensor array 400 that need to be

sampled. If all the rows in sensor array 400 have been sampled in accordance with

blocks 500-520 (the "Yes" prong of block 525), the same process is used to

acquire a capacitance value for each column of sensor elements in sensor array 400

(block 535). Once all rows and all columns have been processed in accordance with

blocks 500-535, the entire process is repeated (block 540). If, on the other hand,

there are rows in sensor array 400 that have not been sampled in accordance with

blocks 500-520 (the "No" prong of block 525), the next row is selected (block

530) and the acts of blocks 500-525 are performed. [0018] In one illustrative embodiment: sensor array 400 comprises a 16x32

capacitive grid, providing 48 output channels; Vcc is 3.3 volts; storage capacitor 415

is approximately 10,000 picofarads, an average row capacitance value is

approximately 12 picofarads; an average column capacitance value is approximately

9 picofarads; the average change in capacitance of a row or column electrode due to

a user's finger touching sensor array 400 is approximately 0.2 picofarads; the

threshold value at which a digital capacitance value is obtained is 1.6 volts; and the

rate at which MUX circuits 410, 420 and 425 are switched is 6 megahertz. It has

been found, for these values, that its takes approximately 580-600 sample cycles to

charge storage capacitor 415 to the threshold voltage. In one embodiment, the

digital capacitance value is, in fact, a count of the number of sampling cycles

required to charge storage capacitor 415 to the threshold value. One of ordinary

skill in the art will recognize that this value is directly related to the sensor element's

(e.g., row or column) capacitance value. In this embodiment, scan circuit 325 (in

conjunction with MUX circuits 410, 420 and 425 and storage capacitor 415)

measures each of the 48 sensor array outputs 125 times each second, with each

measurement comprising a 10-bit value (unsigned integer). Referring to the 48

measurements acquired by scan circuit 325 from sensor array 400 in each of the

125 epochs as a frame, the illustrative track pad sensor device generates:

f 48 channels Y 10 bits Yl 25 framesYl byte λ _ bytes/

I frame AchannelΛ second Λ 8 bits J ^~ ' /second¹

[0019] As noted with respect to FIG. 2 and as further shown in FIG. 3, driver

application 350 is executed general purpose processing unit 360 that is also responsible for executing user applications and tasks, e.g., 365. That is, in

accordance with the invention raw track pad sensor data is analyzed by one, or

more, general purpose processing units associated with the host computer system

and not by a dedicated processor or processing circuit(s) associated with track pad

device 300. A direct consequence of the architecture of FIGS. 2 and 3 is that the

processing resources (e.g., CPUs) tasked with analyzing track pad sensor data must

be shared with other computer system processing needs such as other system level

and user level applications.

[0020] Various changes in the materials, components and circuit elements of

the described embodiments are possible without departing from the scope of the

following claims. Consider, for example, the system of FIG. 3. Other embodiments

could include a smaller (e.g., 10x16) or larger (e.g., 32x32) sensor array 305.

Further, frame rates other than 125 Hertz ("Hz") and sample resolutions other than

10 bits are possible. It will also be understood that the host computer system may

comprise more than one general purpose processing unit (e.g., processor 250). In

addition, some of the circuitry identified in FIGS. 2 and 3 as being integral to track

pad device 205 or 300 may be embodied in circuitry also used for other functions.

For example, transmit circuits 230 and 330 may be shared by other USB input

devices such as, for example, a keyboard. In addition, one of ordinary skill in the art

will recognize that the invention is also applicable to track pad sensor devices that

are pixilated rather that row-column addressable. It will be further recognized that

the operational procedure outlined in FIG. 5 may be modified. For instance, sensor

column values may be obtained before sensor row values. Alternatively, sensor row and sensor column data may be interlaced and/or measured at the same time. In

any event, it will be recognized that scan circuit 325 measures sensor pad

characteristic values (e.g., capacitance or resistance) in a set order and that this

order must be known or communicated to driver application 350. In yet another

embodiment, scan circuit 325 may measure sensor characteristic values in any

convenient manner and reorder them into a sequence known or expected by driver

application 350 prior to transmission by transmit circuit 330.

Claims

What is claimed is:

1. A track pad input device, comprising:

a capacitive track pad sensor having a plurality of sensing elements, each

sensing element associated with a region of the capacitive track pad sensor;

a data acquisition circuit electrically coupled to the capacitive track pad sensor

for selectively encoding digital capacitance values for each of the plurality of sensing

elements; and

a communication circuit for transmitting the digital capacitance values to a

host processor for processing, wherein the host processor is also at least partially

responsible for executing user-level tasks.

2. The track pad input device of claim 1, wherein the communication circuit

comprises a circuit for transmitting the digital capacitance values in accordance with

a universal serial bus protocol.

3. The track pad input device of claim 1, wherein the data acquisition circuit is

adapted to repeatedly encoding digital capacitance values for each of the plurality of

sensing elements.

4. The track pad input device of claim 1, wherein the track pad input device

does not include a means for analyzing the encoded digital capacitance values.

5. A track pad input device consisting essentially of:

a track pad sensor having a plurality of sensing elements, each sensing

element associated with a region of the track pad sensor;

a data acquisition circuit for selectively encoding a digital value representing a

characteristic for each of the plurality of sensing elements; and

a communication circuit for transmitting the encoded digital values to a host

processor for analysis, wherein the host processor is also at least partially

responsible for executing user-level tasks.

6. The track pad input device of claim 5, wherein the sensor element comprises

a resistive sensor array.

7. The track pad input device of claim 5, wherein the sensor element comprises

a capacitive sensor array and each encoded digital value represents a capacitance

value.

8. The track pad input device of claim 5, wherein the data acquisition circuit is

adapted to repeatedly encode digital values for each of the plurality of sensing

elements.

9. The track pad input device of claim 5, wherein the communication circuit is

adapted to transmit the encoded digital values in accordance with a universal serial

bus protocol.

10. A track pad input device comprising:

a track pad sensor having a plurality of sensing elements, each sensing

element associated with a region of the track pad sensor;

means for measuring a digital value for each of the plurality of sensing

elements, the measured digital value representing a characteristic of the sensing

element; and

means for transmitting the plurality of measured digital values to a host

processor for processing, wherein the host processor is also at least partially

responsible for executing user-level tasks.

11. The track pad input device of claim 10, wherein the track pad input device

does not include a means for determining a user action corresponding to

manipulation of the track pad sensor.

12. The track pad input device of claim 10, wherein the track pad sensor

comprises a resistive sensor array.

13. The track pad input device of claim 10, wherein the track pad sensor

comprises a capacitive sensor array.

14. The track pad input device of claim 13, wherein the means for measuring

comprises:

means for selectively stimulating each of the plurality of sensing elements;

means for determining a time required to stimulate each selected sensing

element to a specified event; and

means for encoding the determined time into a digital value.

15. The track pad input device of claim 14, wherein the specified event comprises

charging a known capacitance to a specified voltage.

16. The track pad input device of claim 10, wherein the means for transmitting

comprises a means for transmitting the measured digital values to the host

processor in accordance with a universal serial bus protocol.

17. A track pad input method, comprising:

stimulating a plurality of sensor elements in a track pad sensor;

measuring a characteristic for each of the stimulated sensor elements, each

measurement being encoded by a digital value;

transmitting the measured digital values to a host processor wherein the host

processor is responsible, at least in part, for executing user-level tasks;

analyzing, with the host processor, the measured digital values; and

generating a signal representing a track pad input action based on the

measured digital values.

18. The method of claim 17, wherein the act of stimulating comprises stimulating

a capacitive track pad sensor element.

19. The method of claim 18, wherein the act of measuring a characteristic

comprises determining a digital value representing a capacitance value.

20. The method of claim 17, wherein the act of transmitting comprises

transmitting the measured digital values in accordance with a universal serial bus

protocol.

21. The method of claim 17, wherein the act of generating comprises generating

a signal encoding a cursor movement action.

22. The method of claim 17, wherein the host processor is one of a plurality of

processors associated with a host computer system.

23. The method of claim 22, wherein the act of analyzing is performed by one or

more of the plurality of processors.

24. A computer system, comprising:

one or more host processors for executing, at least in part, user-level tasks;

a display unit operatively coupled to the host processor;

a first communication circuit operatively coupled to the host processor; and

a track pad input device comprising -

a track pad sensor having a plurality of sensing elements, each sensing

element associated with a region of the track pad sensor;

a data acquisition circuit electrically coupled to the track pad sensor for

selectively encoding a digital value representing a characteristic

for each of the plurality of sensing elements; and

a second communication circuit for transmitting the encoded digital

values to the first communication circuit, where after at least

one of the one or more host determine an action corresponding

to manipulation of the track pad sensor.

25. The computer system of claim 24, wherein the first and second

communication circuits are adapted to operate in accordance with a universal serial

bus protocol.

26. The computer system of claim 24, wherein the track pad sensor comprises a

resistive sensor array.

27. The computer system of claim 24, wherein the track pad sensor comprises a

capacitive sensor array.

28. The computer system of claim 27, wherein the data acquisition circuit

comprises:

means for selectively stimulating each of the plurality of sensing elements;

means for determining a time required to stimulate each selected sensing

element to a specified event; and

means for encoding the determined time into a digital value.

29. The computer system of claim 28, wherein the specified event comprises

charging a known capacitance to a specified voltage.

30. The computer system of claim 24, wherein the data acquisition circuit is

elements.

31. The method of claim 17, wherein the act of analyzing comprises determining

a single finger is manipulating the track pad sensor.

32. The method of claim 31, wherein the act of generating a signal comprises

indicating a single-finger gesture.

33. The method of claim 32, wherein the single-finger gesture comprises a single

click action.

34. The method of claim 32, wherein the single-finger gesture comprises a drag

operation.

35. The method of claim 32, wherein the single-finger gesture comprises a select

operation.

36. The method of claim 17, wherein the act of analyzing comprises determining

multiple fingers are simultaneously manipulating the track pad sensor.

37. The method of claim 36, wherein the act of generating comprises generating

a signal indicating a multi-finger gesture.

38. The method of claim 36, wherein the multi-finger gesture comprises a double¬

click operation.

39. The method of claim 36, wherein the multi-finger gesture comprises a visual

zoom operation.

40. A track pad input method, comprising:

stimulating a plurality of sensor elements in a track pad sensor using a single

finger;

measuring a characteristic for each of the stimulated sensor elements, each

measurement being encoded by a digital value;

transmitting the measured digital values to a host processor wherein the host

processor is responsible, at least in part, for executing user-level tasks;

analyzing, with the host processor, the measured digital values; and

generating a signal representing a single-finger gesture based on the

measured digital values.

41. The method of claim 40, wherein the act of generating a signal representing a

single-finger gesture comprises generating a signal representing a single click action.

42. The method of claim 40, wherein the act of generating a signal representing a

single-finger gesture comprises generating a signal representing a drag operation.

43. The method of claim 40, wherein the act of generating a signal representing a

single-finger gesture comprises generating a signal representing a select operation.

44. A track pad input method, comprising:

stimulating a plurality of sensor elements in a track pad sensor using multiple

fingers simultaneously; measuring a characteristic for each of the stimulated sensor elements, each

measurement being encoded by a digital value;

transmitting the measured digital values to a host processor wherein the host

processor is responsible, at least in part, for executing user-level tasks;

analyzing, with the host processor, the measured digital values; and

generating a signal representing a multi-finger gesture based on the

measured digital values.

45. The method of claim 44, wherein the act of generating a signal representing a

multi-finger gesture comprises generating a signal representing a double-click

operation.

46. The method of claim 44, wherein the act of generating a signal representing a

multi-finger gesture comprises generating a signal representing a visual zoom

operation.