CA2011204C

CA2011204C - Electronic blackboard interface

Info

Publication number: CA2011204C
Application number: CA 2011204
Authority: CA
Inventors: Lucien Potvin
Original assignee: University of Ottawa
Current assignee: University of Ottawa
Priority date: 1990-02-28
Filing date: 1990-02-28
Publication date: 1995-02-07
Anticipated expiration: 2010-02-28

Abstract

ABSTRACT
The present invention relates to an interface for an electronic blackboard and more particularly to a method and apparatus for determining the X-Y coordinates of a point on a writing surface and the output of the point on a video display device on a real-time basis. The electronic blackboard display system has both a contact mode and a self-calibration mode. The self-calibration mode is functional during times of non-contact. Contact signals from the electronic blackboard are digitized and displayed on a video display terminal in a colour corresponding to a pen tray signal. The microprocessor can also output signals through a modem to a remote video display terminal.

Claims

1. An electronic blackboard display system comprising:
(i) An electronic blackboard having first and second spaced apart electronically conductive surfaces, each said surface having a pair of approximately parallel electrodes proximate to the ends of each surface, the electrodes of the first surface being approximately orthogonal to the electrodes of the second surface, at least one surface being sufficiently resilient to permit contact between the surfaces upon application of pressure;
(ii) a voltage source capable of being connected to each pair of parallel electrodes which, when connected to the first or second set of parallel electrodes respectively when contact is present, will cause a first or second signal respectively to be generated;
(iii) a microprocessor in which said first and second contact signals are processed;
(iv) a contact determination circuit into which said first and second contact signals are inputted, said contact determination circuit generating a contact signal or no-contact signal which is processed by said microprocessor;
(v) a video display terminal controlled by said microprocessor, said video display terminal receiving its input from said microprocessor;
Whereby when said first and second contact signals indicate no contact, a self-calibration circuit is activated for self-calibration of said electronic blackboard; and when said first and second contact signals indicate a contact signal, the self calibration circuit is deactivated and said microprocessor causes said video display terminal to output a video display signal dependent upon said first and second contact signals.

2. Apparatus as claimed in claim 1 wherein the signal output from the microprocessor to the video display terminal in response to a contact signal causes the video display terminal to display a signal corresponding to the point of contact on the electronic blackboard.

3. Apparatus as claimed in claim 2 wherein said electronic blackboard display system further comprises a pen tray, said pen tray connected to said microprocessor, said pen tray causing a pen signal to be input to said microprocessor corresponding to a location from which a pen is removed from said pen tray.

4. Apparatus as claimed in claim 2 further containing a modem circuit, said modem circuit controlled by said microprocessor, said modem circuit outputting a signal in response to said first and second contact signals when contact is present.

5. Apparatus as claimed in clain 3 wherein said pen signal causes said microprocessor to output a colour signal to said video display terminal whereby the signal displayed by said video display is of a predetermined colour corresponding to said pen signal.

6. A method of self-calibration for an electronic blackboard display system having first and second spaced-apart electronically conductive surfaces, each said surface having a pair of approximately parallel electrodes proximate to the ends of each surface, the electrodes of the first surface being approximately orthogonal to the electrodes of the second surface, at least one surface being sufficiently resilient to permit contact between the surfaces upon application of pressure, a voltage source capable of being connected to each pair of parallel electrodes which, when connected to the first or second set of parallel electrodes respectively when contact is present, will cause a first or second signal respectively to be generated, and when contact is not present, causing at least one non-contact signal to be generated, said method comprising the following steps when a non-contact signal is generated:
(i) applying a voltage to the parallel electrodes of the first surface, said second electrodes having no voltage applied directly to them;
(ii) connecting a voltage measuring circuit first to one parallel electrode of the second surface and recording the measured voltage;
(iii) connecting a voltage measuring circuit to the other parallel electrode of the second surface and recording the measured voltage.

(iv) applying a voltage to the parallel electrodes of the second surface, said first electrodes having no voltage directly applied to them;

(v) connecting a voltage measuring circuit to one parallel electrode of the first surface and recording said measured voltage;
(vi) connecting a voltage measuring circuit to the other parallel electrode of the first surface and recording the measured voltage.
(vii) converting each of said four measured voltages to digital data;
(viii) determining whether or not said measured voltages are within a pre-defined range;
(ix) updating previously recorded measurements with new measurements on a continuous basis.

7. The method of claim 6 wherein a contact determination circuit is connected and disconnected to said electronic blackboard display system at predetermined time intervals, and if contact is detected, said display system switches from a self-calibration mode to a contact mode causing a signal corresponding to said contact signals to be displayed on said video display.