GB2486300A

GB2486300A - Synchronous optical data link

Info

Publication number: GB2486300A
Application number: GB201117331A
Authority: GB
Inventors: Richard Georde Hoptroff
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-10-07
Filing date: 2011-10-07
Publication date: 2012-06-13
Anticipated expiration: 2031-10-07
Also published as: GB201117331D0; GB2486300B; WO2013050742A1

Abstract

This invention relates to the problem of communicating information from a device such as a PC (101), having an extensive user interface including visual display screen, to a portable electronic device (201), such as a wristwatch, with limited user interface. The method uses multiple photosensors (202 204) on the receiving device (201) to receive spatially- and temporally- varying data optically from the visual display of the transmitting device by holding it in close contact. One photosensor (202) receives a synchronous binary clock signal (102) from one area of the screen. One or more further photosensors (204) receive data signals (104) from other areas of the screen that are synchronized to the clock signal. Further photosensors (203) may receive signals (103) from areas with constant or inverting colour levels to serve as references to which the other photosensor signals are compared. The synchronous binary clock signal (102) is either in a first validity state indicating that the data signal (104) is valid, or in a second validity state indicating that the data signal (104) is transitioning to the subsequent data bit.

Description

SYNCHRONOUS OPTICAL DATA LINK METHOD

As the power of embedded computing increases, a rising problem is that of getting information into and out of small electronic devices with limited user interfaces. This invention only examines the issue of getting data into such devices, at low data rates, targeting minimal cost, size and design compromise. The embodiment presented involves a wristwatch as an example, but the relevance is more widespread.

The most common method of exchanging data with such embedded devices is a cable link such as a USB cable. This has associated problems, including the cost of the socket on the device, the cable cost, the socket's bulkiness and the non-waterproof nature of the most connectors. Wireless technologies such as Bluetooth Low Energy avoid some of these limitations, but still suffer from high cost and antenna physical requirements, and additionally have regulatory certification requirements.

A fundamental limitation of such approaches is that the software application that serves as a transmitting device is increasingly likely to be browser-based, originating from a remote web server. This has the advantage that the information provider retains control over the software and the data it transmits; equally the user's preference for one particular operating system over another, or indeed their preference for PCs over smartphones, is immaterial, since nothing needs to be installed by the user. The problem is that for reasons of security, it is not possible to allow a web application to take over any of the transmitting device's peripherals such as its USB and Bluetooth ports. The most they can do reliably and repeatedly, across the range of available devices, is to generate a series of images on a screen. Not even audio can be assumed to be available on all devices.

The temptation therefore is to look for way to provide an optical communications link from a device screen such as a web browser window to a limited user-interface device. Such an idea is not new; Timex's DataLink product line originally had such an optical link. US 5,488,571, assigned to Timex Corp, disclosed a system wherein an image was displayed on a frame-scanning CF{T screen. At the photosensor, which accepted light from the whole screen area, this was detected as a serial data signal as the scan illuminated successive scan lines of the screen. Data was thus transmitted as an asynchronous time-varying serial signal. Unfortunately, the asynchronous approach required low-level control of the system timing to ensure that the frame was updated during the fly-back between complete frame scans. This became increasingly problematic as operating systems became abstracted from the hardware they ran on.

US 5,742,260, assigned to Microsoft Corp, improved on the system by providing a displayed image that would remain static for at least one complete CRT frame scan. The first and last fields illuminated in the frame provided synchronization -they both inverted in successive frames. If the receiving photosensor observed the synchronization fields had different values, it would infer that the frame data was changing and the data should be ignored. If the receiving photosensor determined that the fields had the same value, it would infer that the data in the frame was intact and complete. If the synchronization fields both had the same value as the previous complete frame, then the frame was determined to be a duplicate and was discarded. Only if the synchronization fields were different from the last complete frame was the data judged to be valid.

Two limitations of the approach result from the need for the photosensor to collect light from the entire frame-scanned image. The first limitation is that the illumination will be uneven and therefore subject to interference from ambient light, making it difficult to identify the required signal without some kind of reference level.

The second limitation is that the photosensor interprets a frame-scanned image, what we perceive as a 2-dimensional image, as a 1-dimensional time-varying signal. With the advent of LCD screens, e-ink displays, etc, such frame-scanning no longer occurs. With browser-based provision of information, no assumption can even be made as to how many scan lines or pixels constitute the displayed image.

Timex's DataLink system eventually migrated to a USB interface, presumably because of these limitations.

An alternate approach is to display a static bar code on the screen and to use a complex optical sensor such as a CCD array to detect and process it. This is highly effective is some applications, particularly where a printout of the image might be advantageous. However, the currently available receiver sensors are all too bulky, power hungry and expensive to be considered in low cost, compact, embedded computing applications such as wristwatches.

This invention combines the time-varying nature of the DataLink approach with the spatially-varying nature of the bar-code approach, using a limited number of compact, low-cost photosensors and associated circuitry, and making no assumptions about the scanning nature of the display device beyond the existence of a minimum duration for which the display will reliably reproduce the required complete image.

According to a first aspect of the invention, there is a provided a timepiece comprising at least one photosensor for optically monitoring a visual display unit to receive a data signal comprising a sequence of data bits, the sequence including a data bit and a subsequent data bit each being in a first or second state, and to receive only one validity signal being in either a first validity state or a second validity state, the first validity state indicating that the data bit is valid, and the second validity state indicating that the data signal is transitioning to the subsequent data bit in the sequence; memory means for storing the data bit; and processing means, configured to store the data bit on the memory means when the validity signal is in the first validity state.

According to a second aspect of the invention, there is provided a method comprising the steps of: displaying a data field on a visual display unit, the data field configured to display a sequence of data bits, including a data bit and a subsequent data bit, each in a first or second data state; and displaying only one validity field on the visual display unit, having a first and second validity state, wherein the first validity state indicates that the data bit is valid and the second validity state indicates that the data field is transitioning to the subsequent data bit in the sequence.

With reference to figures 1 -5, the invention is a method comprising the following aspects: 1. Transmitting device (101') such as a PC or mobile phone displays two or more blocks (102', 103', 104') of solid colour on its display screen (105'). The transmitting device can change the colour states displayed by each block over time, with the exact sequence of colour states and minimum duration of each colour state being assured, but not necessarily the exact timing of the state transitions.

2. Receiving device (201') has corresponding photosensors (202', 203', 204') mounted such that, when receiving device (201') is placed in close proximity to display screen (105') in a specified orientation, each photosensor (202', 203', 204') receives light from a different block (102', 103', 104'; figure 3) and thus is excited according to the brightness of that individual block.

3. One block (102') acts a synchronous clock. One or more blocks (e.g. 104') provide data in synchrony with the clock. The clock and data blocks exist in one of two states, being light or dark colour, to provide binary signals. The state of the clock signal (401') indicates data validity. When it is in one state (403'), it signifies that the data signals (402') are valid and will not change (405'). When the clock signal is in the other state (404'), it indicates that the data blocks are transitioning (406') to their next state in their temporal sequence.

4. In the receiver's electronic circuit, the output of each data photosensor (204') is fed to a shift register memory, such as a microcontroller synchronous serial port (501'), clocked by the output of the clock photosensor (201).

5. Optionally, one or more blocks (103') may be held at a mid-brightness colour, or inverted colour information-containing blocks (102', 104'). Binary signals (401', 402') are then determined by comparing the level of excitation of the photosensors (202', 204') associated with the signal sources each relative to the excitation of the photosensor (203') associated with the mid-brightness or inverted blocks (103'), for purposes of filtering out ambient light signals.

6. Optionally, different information-containing blocks (102', 104') may display different pixel colours commonly found in colour displays (red, green and blue) and the corresponding photosensors (202', 204') be sensitive to those specific colours, either by intrinsic design or through colour filters. The blocks may then merge to reduce the burden of correct orientation of receiver (201') on the screen (205').

7. Filtering of the received signal may optionally be employed, most notably low-pass filtering to suppress any fluctuations associated with scanning effects at sub-frame rates; notch filtering at mains frequencies to reduce the impact of artificial ambient lighting; hysteresis in the comparison of the information-containing blocks (102', 104') with the mid-brightness block (103') to reduce state transition jitter.

8. For successful communication, the minimum duration of each colour state must be below the frame rate of display screen (105'). Optionally, the minimum duration of each colour state may be selectable by the user of transmitting device (101') according to the optimum trade-off between successful transmission and total transition time for that specific transmitting device.

9. Optionally, the photosensors are only exposed to light when a cover is removed.

When the cover is in place, they are in darkness. In this case, the voltage on one of photosensors (e.g. 203') can be monitored using a comparator or analog-to-digital converter to determine when communication may occur.

10. Optionally, when communications are not in progress, the photosensors may additionally be employed to allow the user to convey basic information, for example acknowledging an alarm state, by manually covering and uncovering the photodiodes in a prescribed sequence.

11. Some form of higher-level error detection and correction will be required to determine whether the transmission process has succeeded or failed. Equally, some form of indication on the receiver must communicate this determination to the user and/or the transmitting device. The exact nature of these processes is not considered in this invention.

The embodiment of the invention that follows is a wristwatch that can be customized by means of the optical link, for example to program it with the current time and date, and/or to set user preferences such as daylight savings adjustment rules. The embodiment attempts to implement the invention as cheaply as possible using existing technologies, processes and supply chains.

The photodiodes are placed on the back of the wristwatch in a vertical line. One photodiode (203') is deliberately placed centrally and receives light from a grey coloured reference light level block (103'). The top photodiode (202') receives the clock signal (102') and the bottom photodiode (204') receives the single data signal employed by the embodiment (104').

The watch back may employ a clear window, such as is sometimes used to display the rotating mechanical weight in a self-winding mechanical watch, to provide communications without removing the back. This would be the case if aspect 10 above of the invention were implemented, i.e. additionally using the photodiodes for user input.

Alternatively, the watch back may be opaque and the photodiodes might only be illuminated when the back is removed. This would be the case if aspect 9 above of the invention were implemented, and would certainly be acceptable in many applications, where communications are required only after a battery change.

The source of the transmitted data is a web site that generates a web page containing JavaScript commands. When it appears in a browser window, three horizontal bars are displayed, proscribed by the JavaScript to be each 1cm in width and 5cm in length, in addition to a start' button that initiates the JavaScript program that sequences the colour changes. The central bar provides a mid-level grey reference; the top bar provides a black-or-white clock signal; the bottom bar provides a black-or-white data signal. Additionally, a slider or similar control may also be provided to allow the user to select the minimum duration of each colour state, according to aspect 8 above of the invention. Since some browsers such as small-screen smartphones may compromise the requested dimensions of the bars, a second slider or similar control may allow the block pattern to be enlarged or reduced.

The user holds the back of the watch up against the browser window on the display screen, appropriately aligned with the colour blocks, and presses the Start button. The JavaScript program then cycles through the required sequence of black and white blocks for clock and data, employing the window.setTimeout() function to guarantee a minimum period between colour transitions.

The preferred embodiment of the receiver circuit is given in figure 6. Resistors 602', 603', and 604' are placed in series with each of the photodiodes 202' (clock), 203' (mid-level reference) and 204' (data) to form potential dividers between power ground 601' and sensor excitation current source 608', such that the divided voltages at 614', 615' and 616' vary with the level of incident light.

Capacitors 605', 606' and 607' may provide low-pass filtering such that any sub-frame-rate fluctuations in light level incident on photodiodes 202', 203 and 204' are filtered out.

Comparators 609' and 610' compare clock and data signals 614' and 616' to the mid-level signal 615' to obtain binary clock and data inputs to a synchronous serial port 501' on microcontroller 617'. (Indeed, comparators 609' and 610' may also be integral to microcontroller 617'.) Resistors 611' and 612' provide weak positive feedback to the comparator inputs so they exhibit hysteresis in order to avoid signal jitter during state transitions.

Resistor 603' is chosen to be a slightly different value to resistors 602' and 604' so that roughly equal illumination, the most likely state of light incident on the photodiodes 202', 203', 204' when idle and not receiving communications, does not unduly cause comparators 611' and 612' to change state. Resistor 603' might be chosen such that, when idle, the comparators 609' and 610' would be very unlikely to report that centrally-placed photodiode 203' is more illuminated than the diametrically peripheral photodiodes 202' and 204'. Microcontroller 617' might then reasonably infer that peripheral photodiodes 202' and 204' were being obscured by user intervention, according to aspect 10 of the invention.

In an alternate embodiment, mid-level signal 615' is also provided to analog-to-digital converter or comparator 613' in microcontroller 617' for determining when the back of the watch has been removed. This may serve several purposes: (a) For activation of the sensing synchronous signal sensing circuit.

(b) To move display pointers to reference positions in anticipation of possible removal of the battery.

(c) To store data stored in volatile memory, such as the current time or the position of display pointers, in non-volatile memory in anticipation of possible removal of the battery.

In alternative embodiments, other methods may be used to activate the sensing circuit: (a) It may be active all the time.

(b) It may be activated by pressing a sequence of buttons with the period ending after a fixed duration and/or an instruction sent from the transmitting device.

It may be active for a period after insertion of the battery, with the period ending after a fixed duration and/or an instruction sent from the transmitting device.

Claims

CLAIMS1. A timepiece comprising at least one photosensor for optically monitoring a visual display unit to receive a data signal comprising a sequence of data bits, the sequence including a data bit and a subsequent data bit each being in a first or second state, and to receive only one validity signal being in either a first validity state or a second validity state, the first validity state indicating that the data bit is valid, and the second validity state indicating that the data signal is transitioning to the subsequent data bit in the sequence; memory means for storing the data bit; and processing means, configured to store the data bit on the memory means when the validity signal is in the first validity state.
2. A timepiece as claimed in Claim 1, comprising a first photosensor, for optically monitoring a visual display unit to receive a data signal comprising a sequence of data bits, the sequence including a data bit and a subsequent data bit each being in a first or second state, and a second photosensor, for optically monitoring the visual display unit to receive only one validity signal being in either a first validity state or a second validity state, the first validity state indicating that the data bit is valid, and the second validity state indicating that the data signal is transitioning to the subsequent data bit in the sequence.
3. A timepiece as claimed in Claim 1 or Claim 2, further comprising a third photosensor for optically monitoring the visual display unit to receive a reference signal, the reference signal having a predetermined brightness between a brightness of the data signal and of the validity signal.
4. A timepiece as claimed in any one of the preceding claims, further comprising a photosensor cover, configured to move between a first cover state, wherein the photosensors are optically blocked, and a second cover state.
5. A timepiece as claimed in Claim 4, wherein the processing means is activated when the photosensor cover is moved to the second cover state.
6. A timepiece as claimed in Claim 4, wherein the memory means comprises volatile memory means and non-volatile memory means, wherein any data stored on the volatile memory means is moved to the non-volatile memory means when the photosensor cover is moved to the second cover state.
7. A timepiece as claimed in Claim 4, further comprising a pointer, wherein the pointer is moved to a reference position when the photosensor cover is moved to the second cover state.
8. A method comprising the steps of: displaying a data field on a visual display unit, the data field configured to display a sequence of data bits, including a data bit and a subsequent data bit, each in a first or second data state; and displaying only one validity field on the visual display unit, having a first and second validity state, wherein the first validity state indicates that the data bit is valid and the second validity state indicates that the data field is transitioning to the subsequent data bit in the sequence.
9. A method as claimed in Claim 8, further comprising the step of: displaying a reference field on the visual display unit, having a predetermined brightness between a brightness of the data field and of the validity field.
10. A method as claimed in either Claim 8 or Claim 9, further comprising the steps of: displaying a time input field on the visual display unit, configured to receive a time command from a user indicating a minimum time; and configuring the data field such that the data bit is displayed for at least the minimum time.
11. A method as claimed in any one of Claims 8 to 10, further comprising the steps of: displaying a size input field on the visual display unit, configured to receive a size command from a user indicating a size of the data and validity fields; and configuring the size of the data and validity fields according to the size command from the user.
12. A computer-readable medium having computer-executable instructions adapted to cause a computer system to perform the method of any one of Claims 8 to 11.
13. A timepiece substantially as herein described with reference to and as shown in any one of the accompanying drawings.
14. A method substantially as herein described with reference to and as shown in any one of the accompanying drawings.
15. A computer-readable medium substantially as herein described with reference to and as shown in any one of the accompanying drawings.Amendments to the claims have been filed as follows: cLAIMS 1. An electronic device comprising at least one photosensor for optically monitoring a visual display unit to receive a data signal comprising a sequence of data bits, the sequence including a data bit and a subsequent data bit each being in a first or second state, and to receive only one validity signal being in either a first validity state or a second validity state, the first validity state indicating that the data bit is valid, and the second validity state indicating that the data signal is transitioning to the subsequent data bit in the sequence; * s* memory means for storing the data bit; and * :* processing means, configured to store the data bit on the memory means when the vaildity signal is in the first validity state. S. *. * S I * S*: !? 2. An electronic device as claimed in Claim 1, comprising a first photosensor, for optically monitoring a visual display unit to receive a data signal comprising a sequence of data bits, the sequence including a data bit and a subsequent data bit each being in a first or second state, and a second photosensor, for optically monitoring the visual display unit to receive only one validity signal being in either a first validity state or a second validity state, the first validity state indicating that the data bit is valid, and the second validity state indicating that the data signal is transitioning to the subsequent data bit in the sequence.3. An electronic device as claimed in Claim 1 or Claim 2, further comprising a third photosensor for optically monitoring the visual display unit to receive a reference signal1 the reference signal at a mid-brightness level between a brightness of the data signal and of the validity signal.4. An electronic device as claimed in any one of the preceding claims, further comprising a photosensor cover, configured to move between a first cover state, wherein the photosensors are optically blocked, and a second cover state.5. An electronic device as claimed in Claim 4, wherein the processing means is activated when the photosensor cover is moved to the second cover state.ft. ft * * . r'°: 6. An electronic device as claimed in Claim 4, wherein the memory means comprises *. volatile memory means and non-volatile memory means, wherein any data stored on the volatile memory means is moved to the non-volatile memory means when the * *. photosensor cover is moved to the second cover state.* S ft * ft *ft * ft * I. 7. An electronic device as claimed in Claim 4, further comprising a painter, wherein the pointer is moved to a reference position when the photosensor cover is moved to the second cover state.8. An electronic device as claimed in any one of the preceding claims, being a timepiece.9, Amethodcompdsftgthestepsof displaying a data field on a visual display unit, the data field configured to display a sequence of data bits, including a data bit and a subsequent data bit, each in a first or second data state; and displaying only one validity field on the visual display unit, having a first and S second validity state, wherein the first validity state indicates that the data bit is valid and the second validity state indicates that the data field is transitioning to the subsequent data bit in the sequence.10. A method as claimed in Claim 9, further comprising the step of: *.* .20 displaying a reference field on the visual display unit, having a mid-brightness * level between a brightness of the data field and of the validity field.SI S * S S * **11. A method as claimed in either Claim 9 or Claim 10, further comprising the steps of: r *:* displaying a time input field on the visual display unit, configured to receive a * : *!? time command from a user indicating a minimum time; and configuring the data field such that the data bit is displayed for at least the minimum time.12. A method as claimed in any one of Claims 9 to 11, further comprising the steps of: displaying a size input field on the visual display unit, configured to receive a size command from a user indicating a size of the data and validity fields; and configuring the size of the data and validity fields according to the size command from the user.13. A computer-readable medium having computer-executable instructions adapted to cause a computer system to perform the method of any one of Claims 9 to 12.14. An electronic device substantially as herein described with reference to and as shown in any one of the accompanying drawings.15. A method substantially as herein described with reference to and as shown in any one of the accompanying drawings.* .O
16. A computer-readable medium substantially as herein described with reference to andS*0S5. . * as shown in any one of the accompanying drawings. *5 * * 5 * * S. S. ** * 0 5 * S 5. 1 S *S