Patent Publication Number: US-2002003507-A1

Title: Dual mode digital video interface and remote lcd monitor

Description:
BACKGROUND OF THE INVENTION  
       [0001] Traditionally, video interfaces for display monitors have been based upon analog circuit technology. However, the advent of higher performance digital systems at lower costs allows for the utilization of digital video interfaces. Newer digital video standards have been promulgated by organizations such as the Video Electronics Standards Association (VESA) which specifies a digital interface that provides higher performance, lower cost and support of placing the monitor at greater distances away from a video source such as a computer system. VESA is a standards organization comprised of leading computer, flat panel display, cabling, connector and integrated circuit manufacturers. Digital video interfaces allow computer controlled display systems to be installed in locations and applications where previous systems were too large and too costly for a given performance level to be of any practical value.  
       [0002] One ideal application of a digital interface video system is in transit systems where a computer system coupled to a location database in conjunction with a coordinate positioning and time reference system provides accurate navigation and scheduling information. For example, such a transit system may be utilized in a city busing system wherein the driver of a bus is provided with information on navigating the bus along a predetermined route and whether or not the driver is on an expected schedule. In another example, the transit system may be utilized in an airport parking shuttle service wherein the coordinate locations of customers&#39; vehicles in a large parking facility are stored in the transit system such that the driver of the shuttle may drive each customer to the exact location of the customer&#39;s vehicle based upon navigation with the transit system. Often, the performance and budget constraints of both applications may vary such that a first application may only require a lower performance, lower cost display system whereas a second application may require a higher performance, higher cost display system. The display interface of the transit system ideally would be able to utilize the appropriate display system. However, standards organizations typically specify the latest, highest performance interface standards without regard or consideration to lower performance applications, requiring the design of the transit system to add circuitry in addition to the higher performance interface in order to accommodate a lower cost display system thereby mitigating against the goal of providing a lower cost system. Thus, there lies a need to provide a video display interface that is capable of accommodating at least two types displays without prohibitively increasing the cost or complexity of the display interface.  
       SUMMARY OF THE INVENTION  
       [0003] The present invention is directed to a dual mode digital video interface for coupling a flat panel display to a computer system. In one embodiment, the dual mode digital video interface includes a video controller, disposed in the computer system, for generating a video signal to be displayed on the flat panel display, a first interface for operatively coupling the video controller to the flat panel display in a first display mode when the flat panel display is a first type of display, and a second interface for operatively coupling the video controller to the flat panel display in a second display mode when the flat panel display is a second type of display, the first interface being enabled when the first type of display is coupled to the computer system and the second interface being enabled when the second type of display is coupled to the computer system.  
       [0004] The present invention is further directed to a navigation system for a transit vehicle. In one embodiment, the navigation system includes a computer system, disposed in the transit vehicle, for controlling the navigation of the transit vehicle, a global positioning system receiver, coupled to the computer system, for receiving a positioning and timing reference from a constellation of space vehicles in a global positioning system, a display, coupled to the computer system, for displaying positioning and timing information of the transit vehicle, and a dual mode digital video interface, operatively disposed in the computer system, for providing a first digital interface in a first mode for controlling the display when the display is a first type of display, and for providing a second digital interface in a second mode for controlling the display when said display is a second type of display.  
       [0005] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.  
       [0006] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0007] The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which:  
     [0008]FIG. 1 is a block diagram of the hardware of a computer system operable to tangibly embody the present invention;  
     [0009]FIG. 2 is a block diagram of a dual mode digital video interface in accordance with the present invention;  
     [0010]FIG. 3A is a block diagram of the dual mode digital video interface of FIG. 2 further showing a simple differential interface for coupling to a monochrome LCD and a VESA interface for coupling to a color LCD;  
     [0011]FIGS. 3B and 3C are schematic diagrams of the simple differential interfaces shown in FIG. 3A; and  
     [0012]FIG. 4 is a block diagram of a transit system ideally suitable for utilizing the dual mode digital video interface of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0013] Reference will now be made in detail to the presently preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.  
     [0014] Referring now to FIG. 1, a computer system operable to tangibly embody a dual mode digital video interface in accordance with the present invention will be discussed. The computer system  10  generally comprises a central bus  20  for transferring data among the components of computer system  10 . A clock  12  provides a timing reference signal to the components of computer system  10  via bus  20  and to a central processing unit  14 . The central processing unit  14  is utilized for interpreting and executing instructions and for performing calculations for computer system  10 . A random access memory (RAM) device  16  couples to bus  20  and to central processing unit  14  for operating as memory for central processing unit  14  and for other devices coupled to bus  20 . A read-only memory device (ROM)  18  is coupled to the components of computer system  10  via bus  20  for operating as memory for storing instructions or data that are normally intended to be read but not to be altered except under specific circumstances (e.g., when the instructions or data are desired to be updated). ROM device  18  typically stores instructions for performing basic input and output functions for computer system  10  and for loading an operating system into RAM device  16 .  
     [0015] An input device controller  22  is coupled to bus  20  for allowing an input device  24  to provide input signals into computer system  10 . Input device  24  may be a keyboard, mouse, joystick, trackpad or trackball, microphone, modem, or a similar input device. Further, input device  24  may be a graphical or tactile input device such as a touch pad for inputting data with a finger or a stylus. Such a graphical or tactile input device  24  may be overlaid upon a screen of a display device  28  for correlating the coordinates of a tactile input with information displayed on display  28 . Display  28  is controlled by a video controller  26  that provides a video signal received via bus  20  to display  28 . Display  28  may be any type of display or monitor suitable for displaying information generated by computer system  10  such as cathode ray tube (CRT), a liquid crystal display (LCD), gas or plasma display, or a field emission display panel. Preferably, display  28  is a flat-panel display having a depth being shallower than its width. A peripheral bus controller  30  couples peripheral devices to central bus  20  of computer system  10  via a peripheral bus  32 . Peripheral bus  32  is preferably in compliance with a standard bus architecture such as an Electrical Industries Association Recommended Standard  232  (RS-232) standard, an Institute of Electrical and Electronics Engineers (IEEE) 1394 serial bus standard, a Peripheral Component Interconnect (PCI) standard, or a Universal Serial Bus (USB) standard, etc. A mass storage device controller  34  controls a mass storage device  36  for storing large quantities of data or information, such as a quantity of information larger than the capacity of RAM device  16 . Mass storage device  36  is typically non-volatile memory and may be a disk drive such as a hard disk drive, floppy disk drive, optical disk drive, floptical disk drive, etc.  
     [0016] Referring now to FIG. 2, a block diagram of a dual mode digital video interface in accordance with the present invention will be discussed. The dual mode digital interface system  40  may be tangibly embodied by computer system  10  discussed with respect to FIG. 1. Video controller  26  provides a video output signal for ultimately controlling and driving one or more display monitors  48  or  50 . For example, monitor  48  may include a lower resolution, monochrome, flat panel display  54  while monitor  50  may include a higher resolution, color, flat panel display  58 . Video controller  26  provides an output signal to the input of a higher resolution, color, multiplexed digital video interface  42  and to the input of a lower resolution, monochrome, non-multiplexed digital video interface  44  of computer system  10 . The outputs of interfaces  42  and  44  are transmitted over an interconnect cabling  46  that preferably comprises four twisted wire-pairs. Interconnect cabling  46  is designed to allow runs on the order of ten meters such that a monitor  48  or  50  may be disposed in a position on the order of ten meters away from the location of computer system  10 . Interfaces  42  and  44  preferably utilize low voltage differential signaling such that the power flowing through interconnect cabling  46  is kept low to minimize electromagnetic interference (EMI). Interfaces  42  and  44  include a tri-state driver controller for enabling either one or the other interface depending upon the type of display utilized and coupled to computer system  10 . Monitor  48  likewise includes a lower resolution, monochrome, non-multiplexed digital interface for coupling with interface  44  to drive display  54  when monitor  48  is coupled to computer system  10 , and monitor  50  includes a higher resolution, color, multiplexed, digital interface for coupling with interface  42  when monitor is coupled with computer system  10 .  
     [0017] Referring now to FIG. 3A, a block diagram of the dual mode digital video interface of FIG. 2 further showing a simple differential interface for coupling to a monochrome LCD and a VESA interface for coupling to a color LCD will be discussed. Video controller  26  provides an output signal to both a VESA compliant interface  42  and to a simple differential interface  44 . Interfaces  42  and  44  may be preferably implemented on a single integrated circuit  60  in order to provide a simple, lower cost video display interface capable of operating in one or two modes based upon the type of monitor to be utilized. Monitor  48  likewise includes a simple differential interface  52  for coupling with interface  44  to provide an output signal to monochrome LCD display  54 , and monitor  50  includes a VESA compliant interface  56  for coupling with interface  42  to provide an output signal to color LCD display  58 . VESA compliant interface  42  may support Video Graphics Adapter (VGA) compliant resolutions and beyond and other flat panel display technologies such as active matrix liquid-crystal display (AMLCD), double-layer supertwist nematic (DSTN) or Plasma, and may further incorporate a Transition Minimized Differential Signaling (TMDS), “Plug &amp; Display” coding scheme, Interface  44  may be compliant with VGA or lower resolution standards such as Enhanced Graphics Adapter (EGA), Color Graphics Adapter (CGA), or Monochrome Display Adapter (MDA) resolutions. The signal provided from video controller  26  to display  54  or display  58  is preferably completely a digital signal.  
     [0018] Referring now to FIGS. 3B and 3C, schematic diagrams of the simple differential interfaces shown in FIG. 3A will be discussed. As shown in FIG. 3B, differential interface  44  comprises buffer gates  62  for receiving component video control and data signals from video controller  26 , each gate  62  receiving a corresponding component video signal. The component signals provided to differential interface  44  include a vertical synchronization signal (“VERT SYNC”), a horizontal synchronization signal (“HORZ SYNC”), a pixel data signal (“PIXEL DATA”), and a pixel clock signal (“PIXEL CLK”). Further, a mode select signal (“MODE SELECT”) is provide to an enable input (“ENABLE”) of differential interface  44  for controlling the utilization of differential interface  44 . Likewise, differential interface  52  of monitor  48  comprises buffer gates  64  for receiving component video control and data signals from differential interface  44  via interconnect cabling  46 , each gate  62  receiving a corresponding component video signal. The corresponding component video signals are provided from differential interface  52  to LCD  54  for reproducing the video signal on monitor  48 . The configuration of differential interfaces  44  and  52  provide low voltage differential signaling (LVDS) that is suitable for transferring data at a higher speed and at a lower power data from computer system  10  to monitor  48 . Such a configuration may be utilized, for example, for higher speed transmission (e.g., 20 MHz or greater) of transistor-transistor logic (TTL) signals provided by video controller  26  over longer distances (e.g., at least greater than 1 meter and typically 10 meters or greater) and then converting the signals back into TTL signals that are interpretable by LCD  54 . A similar configuration, configured in compliance with a VESA standard such as TMDS, may also be utilized for interfaces  42  and  56 .  
     [0019] Referring now to FIG. 4, a block diagram of a transit system in which the dual mode digital display interface of the present invention may be utilized will be discussed. The transit system  70  includes a transit vehicle  72  for transporting goods or passengers. Transit vehicle includes an on-board computer system  10  coupled to display  28 . Computer system  10  is coupled with a global positioning system (GPS) receiver  74  and antenna  76  for receiving a positioning and timing reference signal from a constellation of satellites  82 ,  84  and  86  in orbit around the earth. Such a global positioning system may be the NavStar GPS system maintained by the U.S. Government, for example. An operator of transit vehicle may be informed of the coordinate position of transit vehicle  72  and whether transit vehicle  72  is on schedule. Such information may be displayed on display  28  by computer system  10 . Furthermore, computer system  10  may be coupled with a wireless transceiver  78  and antenna  80  for communicating over a wireless network  90  and appropriate antenna system  88  such that information and data may be exchanged between computer system  10  via wireless network  90 . Wireless receiver  78  and GPS receiver  74  may couple with computer system  10  via peripheral bus  32  of FIG. 1. Base station  92  may transfer route and scheduling information for transit vehicle  72  to computer system  10  that is displayed on display  28  and viewed by the operator of transit vehicle  72 . The route and scheduling information may be coordinated with the positioning and timing information received by computer system  10  from GPS receiver  74 . When computer system  10  implements the dual mode digital video interface discussed with respect to FIGS. 2 and 3, display  28  may be freely changed from a first display type (e.g., monochrome LCD) to a second display type without requiring any modification of computer system  10  or installation of additional hardware or software, thereby allowing flexibility in the choice and cost of transit system  70 .  
     [0020] It is believed that the dual mode digital video interface of the present invention and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely an explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.