GB2381584A

GB2381584A - Position measuring method for a flexible keyboard

Info

Publication number: GB2381584A
Application number: GB0125978A
Authority: GB
Inventors: Christopher Chapman; David Lee Sandbach
Original assignee: Electrotextiles Co Ltd
Current assignee: Electrotextiles Co Ltd
Priority date: 2001-10-30
Filing date: 2001-10-30
Publication date: 2003-05-07
Also published as: GB0125978D0

Abstract

A flexible keyboard 101 is pressed at a location 105 to indicate a keystroke. The coordinates of the location pressed can be determined by measuring the voltage produced by an interaction between fabric layers in the keyboard. The interaction produces a voltage signal, and this takes a certain settling time to stabilize. After the voltage has stabilized, it is measured to give the position of the area that has been pressed. If the key is pressed hard, a large voltage signal is produced and only a short time is required before the position can be measured. If the key is pressed lightly, a longer time is required before measurement can be made. In the invention, another parameter of the interaction, e.g. the current it produces, is used to indicate how hard the key was pressed and the settling time is varied according to how hard the key was pressed. This optimises the speed of operation of the keyboard.

Description

Measuring the Position of a Mechanical Interaction Field of the Invention The present invention relates to measuring the position of a mechanical interaction in which voltages are measured after a settling time.

Background of the Invention A position detector is described in British Patent No. 2 341 933 (B), assigned to the present applicant. The response of a detector of this type may be considered in terms of its positional accuracy, the dynamic range of pressure signals and the maximum rate at which positional data may be obtained.

After a mechanical interaction has been made upon the detector, a finite time must elapse before valid information may be derived. The electrical nature of the device introduces a degree of capacitance therefore a settling time must occur before it is possible to obtain positional data. Thus, if a settling time is too long, the response of a device may appear sluggish to users and therefore unacceptable for many applications. Alternatively, if the settling time is too short, there is a risk that invalid positional data will be obtained.

Brief Summary of the Invention According to an aspect of the present invention, there is provided a method of measuring the position of a mechanical interaction in which voltages are measured after a settling time, wherein an additional input signal is related to the extent of the mechanical interaction; and said settling time is modified in response to the size of said additional input signal.

In a preferred embodiment, voltages are applied to a fabric position detector having conducting layers separated by an insulating layer.

In a preferred embodiment, the extent of a mechanical interaction is determined by measuring current.

Brief Description of the Several Views of the Drawings Figure 1 shows a fabric keyboard interfaced to hand held computer. Figure 2 shows examples of an input signal produced in response to manual interactions.

Figure 3 shows an example of an application running on the hand held computer.

Figure 4 shows a schematic representation of the arrangement shown in Figure 1 ; and Figure 5 illustrates operations performed by a micro controller.

Best Mode for Carrying Out the Invention Figure 1 Fabric keyboard 101 is shown in Figure 1, as an example of a device that measures the position of mechanical interactions. Fabric keyboard 101 is interfaced to a hand held computer 102 and when not in use, the fabric keyboard may be wrapped around the hand held computer 102 to provide a degree of protection and to enhance portability. The keyboard 101 includes an array of manually operable keys and manual operation of a key causes fabric layers to be brought into contact thereby allowing electrical conductivity to occur between a first outer layer and a second outer layer through an appropriate inner separating layer.

A voltage is applied to one of said layers to create a voltage gradient across the layer. Voltage is then measured from the second layer such that the level of this voltage will indicate a position of interaction in one dimension. The roles of the layers are then reversed with the voltage gradient in the second layer being generated in a direction substantially perpendicular to the voltage that had been generated in the first layer. In this way, it is possible to identify a y dimensional position for the interaction. Furthermore, when a measurement of this type occurs, the degree of current flow is also measured to thereby provide an indication of the degree of the mechanical interaction.

The present applicant has appreciated that a relatively larger settling time is required when the degree of the mechanical interaction is low.

However, the length of settling time required may be reduced when the degree of the mechanical interaction is relatively high. Thus, in order to improve and enhance overall functionality, the present embodiment is configured such that upon detecting a relatively high level of mechanical interaction, the settling time is reduced.

The present embodiment shows a keyboard communicating with a hand held computer such as that manufactured under the Trademark "Palm". However, in alternative configurations, other processing devices may be used, such as personal computers, mobile telephones or other dedicated processing apparatus. The present invention is also applicable to other positional detecting devices that are not necessarily configured as keyboards.

Figure 2 Two examples of an input signal being produced in response to respective manual interactions are illustrated in Figure 2. Figure 2 plots input signal extent against time. An input signal produced in response to relatively soft key presses is illustrated at 201. Similarly, an input signal produced in response to a relatively hard key press is illustrated at 202. The system has been configured to have a first T1 threshold 203 and a second T2 threshold 204. The system monitors input signals to identify key press interactions that exceed the first threshold level T1. Any input signal having a level below threshold T1 is considered merely to be background noise and is treated as representing an un-pressed state.

In order to identify that a hard key press, such as that represented by input signal 202, is distinct from a soft key presses, such as that represented by input signal 201, a threshold T2 has been established. Thus, as shown in the example, input signal 201 does not exceed threshold T2 and therefore would be considered as a soft key press. Similarly, input signal 202 does exceed threshold level T2 and would therefore be considered as a hard key press.

Figure 3 In this example, the hand held computer is running an application, such as a note pad and as such is configured to record alphanumeric characters in response to manual operation of the keys. As shown in Figure 3, the word"elektex"has been written by pressing the"E""L""E""K"'T'"E" "X"keys. The positional information derived from the keyboard must then be accurate enough to ensure that the desired key is identified otherwise the

keyboard would not be considered in any way useful. Furthermore, a user would only wish to press a key for a finite period of time similar to the length of key press effected when using a standard keyboard. Thus, if it takes too long for a character to be recognised, even when the degree of accuracy is high, this would not be considered acceptable to users.

Figure 4 The combination of a fabric keyboard with a hand held computer is shown schematically in Figure 4. The keyboard 101 includes fabric detector planes 401 and an interface circuit 402. The hand held computer 102 executes programs read from its program memory. An application program could take the form of a note pad, an address book or a diary etc.

Conventionally, hand held computers and similar devices communicate with input devices via their operating system. To effect communication with alternative peripherals, the operating system is enhanced by the inclusion of an appropriate driver, such as keyboard driver 404.

The interface circuit 402 in combination with keyboard driver 404 provides a means of communication between the mechanical detecting planes 401 and the users application program 403.

The interface circuit 402 applies voltages to the planes in order to determine positional data (x y) and extent data z. When data of this type becomes available, it is written to a buffer and the data contained in this buffer may then be read by the keyboard driver 404.

Figure 5 interface circuit 402 includes a micro controller with appropriate program instructions. Program instructions applied to implement the preferred embodiment of the present invention are illustrated in Figure 5.

After start up, a first z value (Z1) is obtained at step 501. At step 502 a question is asked as to whether the z value Z1 is larger than a first threshold value T1. If this question is answered in the negative, the program waits for a pre-determined duration at step 503 whereafter control returns to step 501. In the preferred embodiment, the interface circuit produces z values ranging from zero (0) to two hundred and fifty-five (255) and T1 is set equal to a value of twenty-five (25). Preferably, the wait period at step 503 is set so as to produce a sampling rate of approximately one thousand samples per second.

If the question asked at step 502 is answered in the affirmative, to the effect that the z value Z1 is higher than the first threshold value T1, the interface circuit 402 is instructed to perform a full measurement operation.

A full measurement operation consists of getting an x value and a y value and a further z value representing input signals that may be supplied to the keyboard driver 404. If a z value is received that lies below the first threshold value T1, this is considered to by merely noise and is not interpreted as a mechanical interaction or key press. However, for values higher than threshold value T1, the full measurement is performed.

At step 504 a voltage is supplied to the first plane that is considered as applying the x voltage in order to obtain an x co-ordinate. At step 505 a second z value Z2 is obtained and at step 506 a question is asked as to whether the second z value is larger than the second threshold value T2. If

this question is answered in the negative, the program waits for a predetermined period at step 507. Alternatively, if the question asked at step 506 is answered in the affirmative, the wait process 507 is bypassed and control is sent directly to step 508.

At step 508 an x position is obtained whereafter at step 509 voltage is applied to the second plane in order to obtain a y voltage measurement.

Before the y voltage measurement is obtained, a further z value (Z3) is obtained at step 510. Again, this z value is compared against the second threshold value by the question asked at step 511. Thus, if the third z measurement Z3 is not larger than the second threshold value T2, the program enters a pre-determined wait at step 512. Alternatively, if the third z measurement Z3 is larger than the second threshold value T2, resulting in the question asked at step 511 being answered in the affirmative, wait process 512 is bypassed and control is sent directly to step 513.

At step 513 a y position value is obtained whereafter at step 514 a fourth z value Z4 is obtained. At step 515 the values x, y and Z4 are written to a buffer so that this information may be read by the keyboard driver. At step 516 a question is asked as to whether the process is to continue and if answered in the affirmative control is returned to step 501.

Thus, it should be appreciated that prior to attempting to make a positional measurement, the intensity value is considered. If the intensity value is relatively low, more time is given for the positional data to settle by the inclusion of wait processors 507 and 512. However, when the extent of the mechanical interaction is relatively large, less time is required in order to obtain valid information, therefore less settling time is given and the wait processes are bypassed thereby improving the response of the device.

Thus, positional accuracy is always available but the speed of operation is enhanced when this is possible. In particular, the speed of operation is increased when increases occur to the extent of the mechanical interactions. Thus, in the keyboard environment, the keyboard responds more quickly if the keys are hit more firmly.

As described in the applicants'co-pending patent application (2040P136-GB) it is possible to use a measurement of key pressure in order to control an auto repeat rate. In particular, as pressure is increased, the key repeat rate increases. In order to achieve this, greater demands are placed in terms of obtaining positional data. By incorporating the present invention, it is possible to achieve this given that the x y data rate is increased (by reducing settling time) when a harder key press is made.

Claims

1. A method of measuring the position of the mechanical interaction in which voltages are measured after a settling time, wherein an additional input signal is related to the extent of the mechanical interaction; and said settling time is modified in response to the size of said additional input signal.

2. A method according to claim 1, wherein voltages are applied to a fabric position detector having two conducting layers separated by an insulating layer.

3. A method according to claim 1 or claim 2, where an extent of mechanical interaction is determined by measuring current.

4. A method according to claim 1, wherein said settling time is modified by the introduction of a wait period.

5. A method according to claim 4, wherein said wait period is bypassed upon detection of a hard key press.

6. A method according to claim 1, wherein position is measured to identify a key of a manually operable keyboard.

7. A method according to claim 6, wherein said keyboard is interfaced to a data processing device.

8. A method according to claim 7, wherein an extent of manual interaction is also used to control an operation of said processing device.

9. A method according to claim 8, wherein said operation is an auto-repeat function.

10. A method according to claim 7, wherein said data processing device is a hand held computer.

11. Apparatus for measuring the position of a mechanical interactions in which voltages are measured after a settling time, comprising additional input signal generating means configured to generate an additional input signal related to the extent of the mechanical interaction; and settling time modification means configured to modify said settling time in response to the size of said additional input signal.

12. Apparatus for measuring the position of a mechanical interaction according to claim 11, comprising voltage application means configured to apply voltages to a fabric position detector having two conducting layers separated by an insulating layer.

13. Apparatus according to claim 11 or claim 12, including current measuring means wherein an extent of mechanical interaction is determined

by current measurement.

14. Apparatus according to claim 11, including means for generating a wait period, wherein said settling time is modified by the introduction of said wait period.

15. Apparatus according to claim 14, including bypassing means, wherein said wait period is bypassed by said bypassing means upon detection of a hard keypress.

16. Apparatus according to claim 11, including position measurement means, wherein position is measured to identify a key of a manually operable keyboard.

17. Apparatus according to claim 16, including a data processing device wherein said keyboard is interfaced to said data processing device.

18. Apparatus according to claim 17, wherein operations are performed by said data processing device and one of said operations is controlled by the extent of said manual interaction.

19. Apparatus according to claim 18, wherein said operation is an auto repeat function.

20. Apparatus according to claim 17, wherein said data processing device is a hand-held computer.

21. A method of measuring the position of a mechanical interactions in which voltages are measured after a settling time substantially as herein described with reference to Figure 5.

22. Apparatus for measuring the position of a mechanical interaction in which voltages are measured after a settling time, substantially as herein described with reference to Figures 4 and 5.