Abstract:
An interface for a bulkhead monitor in an in-flight entertainment system, and a method for using the same. More specifically, a one-wire interface use to electrically couple a tapping unit and its associated monitor in an in-flight entertainment system. The wire has a first end for coupling to an input of a comparator in the tapping unit, and a second end for coupling to an input of a comparator in the monitor, to couple the tapping unit to the monitor. The interface further includes a second wire for coupling the wire to a load, such as an indicator which indicates an on or off condition of at least the video monitor. The wire of the interface can also carry a signal indicating a indicating at least one of transmitting state and a receiving state of a microcontroller of the monitor.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
       [0001]    This application claims benefit from U.S. Provisional Patent Application No. 60/855,323, filed on Oct. 30, 2006, the entire content of which being incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an interface for a bulkhead monitor. More specifically, the present invention relates to a one-wire interface for communicating between a tapping unit and its associated monitor in an in-flight entertainment system. 
         [0004]    2. Description of the Related Art 
         [0005]    An in-flight entertainment system, such as those deployed on an aircraft, can comprise a video monitor and a tapping unit. As can be appreciated by one skilled in the art, a tapping unit receives signals, for example, from a communication unit, such as a management terminal, and provides those signals to the video monitor. It is desirable to couple the tapping unit to the video monitor in an efficient manner to avoid special wiring in the in-flight entertainment system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Certain objects and advantages of the present invention will become more apparent by describing in detail a preferred embodiment thereof with reference to the attached drawings in which: 
           [0007]      FIG. 1  is a schematic illustrating an example of an interface between a tapping unit and a video monitor of an in-flight entertainment system according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0008]      FIG. 1  illustrates an example of an interface  100  between a tapping unit  200  and video monitor  300  in an in-flight entertainment system according to an embodiment of the present invention. As illustrated, and as can be appreciated by one skilled in the art, a tapping unit  200  in this example includes a microcontroller  202  that transmits and receives signals to and from the circuitry in the tapping unit  200 . For example, the transmission port  204  of the microcontroller is coupled to the input of an inverter  206  whose output is coupled to an optocoupler  208 . In this example, the output of inverter  206  is coupled to the cathode of a light emitting diode  210  in optocoupler  208 . The anode of the light emitting diode  210  is coupled to a resistor  212  which is further coupled to a DC voltage power supply, such as a +5 volt DC power supply. The optocoupler  208  further includes a transistor  214  as indicated. The collector of the transistor  214  is coupled to the base of a transistor  216 , while the emitter of the transistor  214  is coupled to the negative terminal of power supply  232  (discussed below), which is also coupled to a comparator  218 . 
         [0009]    The receiving terminal  220  of microcontroller  202  is coupled to an optocoupler  222 , as well as resister  224 . Resister  224  is further coupled to a power supply, for example, a +5 volt DC power supply. As indicated, the collector of transistor  226  of the optocoupler  222  is coupled to the receiving terminal  220  of microcontroller  202 , and the emitter of transistor  226  is coupled to ground. The anode of light emitting diode  228  of optocoupler  222  is coupled to a resistor  230 , while the cathode is coupled to the output of comparator  218 . The resistor  230  is further coupled to a power supply  232  which, in this example, is a +28 volt DC power supply. 
         [0010]    A resistor  234  is coupled between power supply  232  and a capacitor  236 , which is further coupled to the negative terminal of the DC power supply  232  (identified as the return +28 V_RTN for the +28V power supply). Resistor  234  is also coupled to the cathode of a zener diode  238 , whose anode is coupled to the negative terminal of the DC power supply  232 . As further illustrated, power supply  232  is coupled to power comparator  218 , and the capacitor  236  and cathode of zener diode  238  are coupled to an input of the comparator  218 . 
         [0011]    As further illustrated, a resistor  240  is coupled between the negative terminal of power supply  232  and the base of transistor  216 , which is further coupled to a resistor  242 . Resistor  242  is therefore coupled between the base of transistor  216  and the positive terminal of power supply  232 . The collector of transistor  216  is coupled to an input of comparator  218 , while the emitter of transistor  216  is coupled to the negative terminal of power supply  232 . 
         [0012]    In addition, a capacitor  244  is coupled between the positive and negative terminals of power supply  232 . The cathode of diode  246  is coupled to the positive terminal of power supply  232 , while the anode of diode  244  is coupled to a resistor  248 . The other end of resistor  248  is coupled to the negative terminal of power supply  232 . 
         [0013]    As further illustrated, and as described in more detail below, a wire of interface  100  is coupled to an input terminal of comparator  218  and the collector of transistor  216 . 
         [0014]    Turning now to the details of the video monitor  300 , video monitor  300  includes a microcontroller  302 . The transmission terminal  304  of microcontroller  302  is coupled to the input of an inverter  306 . The output of inverter  306  is coupled to an optocoupler  308 . In particular, the output of inverter  306  is coupled to the cathode of light emitting diode  310  of optocoupler  308 , while the anode of light emitting diode  310  is coupled to a resistor  312 . The resistor  312  is further coupled to a power supply which, in this example, is a +5 volt DC power supply. The optocoupler  308  further includes a transistor  314 , whose collector is coupled to the base of transistor  316 , while the emitter of transistor  314  is coupled to a comparator  318  and to a negative terminal of power supply  332  (discussed below). 
         [0015]    As further illustrated, the receiving terminal  320  of microcontroller  302  is coupled to an optocoupler  322 . In particular, the receiving terminal  320  is coupled to a resistor  324 , that is further coupled to a power supply which, in this example, is a +5 volt DC power supply. The receiving terminal  320  is also coupled to a collector of transistor  326  of the optocoupler  322 , and the emitter of transistor  326  is coupled to ground. A cathode of light emitting diode  328  of optocoupler  322  is coupled to an output of comparator  318 , while the anode of light emitting  328  is coupled to a resistor  330 . The resistor  330  is further coupled to a power supply  332  which, in this example, is a +28 volt DC power supply and can be the same power supply as power supply  232  discussed above. However, for purposes of this discussion, the power supply relating to the video monitor  300  will be referred to as power supply  332 . 
         [0016]    A resistor  334  is coupled between an input terminal of comparator  318  and the power supply  332 . A capacitor  336  is coupled between another input terminal of comparator  318  and a negative terminal of power supply  332 . Furthermore, the cathode of zener diode  338  is coupled to that input terminal of comparator  318 , while the cathode of zener diode  338  is coupled to the negative terminal of power supply  332 . A resistor  340  is coupled between the positive terminal of power supply  332  and the cathode of zener diode  338 . In addition, a resistor  342  is coupled between the positive terminal of power supply  332  and the base of transistor  316 . A resistor  344  is coupled between the base of transistor  316  and the negative terminal of power supply  332 . The emitter of transistor  316  is also coupled to the negative terminal of power supply  332 . Furthermore, a capacitor  346  is coupled between the positive and negative terminals of power supply  332 . 
         [0017]    In addition, the collector of transistor  316  is coupled to an input of comparator  348 . Comparator  348  is further coupled between a positive and negative terminals of power supply  332 , and an input of comparator  348  is coupled to an input of comparator  318  as indicated. The output of comparator  348  is coupled to an optocoupler  350 . In particular, the output of comparator  348  is coupled to the cathode of a light emitting diode  352  of optocoupler  350 , while the anode of light emitting diode  352  is coupled to a resistor  354 , which is further coupled to the positive terminal of power supply  332 . The collector of transistor  356  of optocoupler  350  is coupled to the positive terminal of power supply  332 , while the emitter is coupled to resistors  360  and  362  that are coupled in parallel to the collector of transistor  316 . A capacitor  358  is also coupled between the positive and negative terminals of power supply  332 . 
         [0018]    In addition, the wire of interface  100  is coupled to the collector of transistor  316 , and thus also coupled to an input of comparator  348 . 
         [0019]    It is noted that the interface  100  is further coupled to a load, such as an indicator lamp, which is coupled to the negative terminal of power supply  232  or  332 . The interface  100  in this embodiment uses the wiring of the in-flight entertainment system of the aircraft in which the tapping unit  200  and video monitor  300  are deployed. It is noted that the interface  100  in this example is an RS-232 interface that conforms to a master-slave protocol. That is, the video monitor  300  is the slave device and does not initiate a communication. Rather, the video monitor  300  transmits in response to a message from the tapping unit  200 , which acts as the master device. The “ON” indicators of the video monitor  300  function when the video monitor  300  interfaces with the tapping unit  200  or another external device, such as a lamp or relay. 
         [0020]    The interface  100  converts the existing discrete line to half duplex RS232 signals for communicating between tapping unit  200  and its associated video monitor  300  in the in-flight entertainment system. In one embodiment, the discrete line used in the interface  100  is the legacy ON INDICATOR wire in the standard cable between the tapping unit  200  and the video monitor  300 . 
         [0021]    During an initial state, the logic of the 1-wire signal on the interface  100  is logic “low” (i.e., zero voltage). After initialized, the microcontrollers  202  and  302  turn optocouplers  208  and  308 , respectively, to an ON state, such that the voltages at the collectors of transistors  226  and  314  are low and the voltages at the cathodes of light emitting diodes  222  and  310  are low, such that transistors  216  and  316  are turned off. The comparator  348  output thus goes low to turn optocoupler  350  ON. The 1-wire signal on interface  100  thus goes to high with +28 VDC. Then, microcontroller  302  in the video monitor  300  is in a receiving mode. 
         [0022]    During a transmitting condition, the microcontroller  300  transmits the RS 232  signals to other line replaceable units (LRUs) in the in-flight entertainment system. Table 1 below indicates low and high conditions for various points circuitry of the tapping unit  200 , the video monitor  300  and the interface  100  and thus, the high and low (on and off) conditions for the transmission mode of the microcontroller  302 . 
         [0000]    
       
         
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                 1-wire 
               
               
                 TX 
                 U3-2, 
                 U3-4, 
                 Q1, 
                   
                   
                 signal 
               
               
                 (+5 V) 
                 U8-2 
                 U8-4 
                 Q2 
                 U2-7 
                 U4 
                 (+28 V) 
               
               
                   
               
             
             
               
                 LOW 
                 HI 
                 HI 
                 ON 
                 HI (U2-6 &lt;7.5 V) 
                 OFF 
                 LOW 
               
               
                 HI 
                 LOW 
                 LOW 
                 OFF 
                 LOW (U2-6 
                 ON 
                 HI 
               
               
                   
                   
                   
                   
                 &gt;7.5 V) 
               
               
                   
               
             
          
         
       
     
         [0023]    During a receiving condition, the microcontroller  300  receives the RS232 signals from other LRUs. Table 2 below indicates low and high conditions for various points circuitry of the tapping unit  200 , the video monitor  300  and the interface  100  and thus, the high and low (on and off) conditions for the receiving mode of the microcontroller  302 . 
         [0000]    
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 1-wire signal 
                   
                   
                 RX 
               
               
                   
                 (+28 V) 
                 U2-1, U6-1 
                 U1-4, U7-4 
                 (+5 V) 
               
               
                   
                   
               
             
             
               
                   
                 HI 
                 HI (U2-3 &gt;7.5 V) 
                 OFF 
                 HI 
               
               
                   
                 LOW 
                 LOW (U2-3 &lt;7.5 V) 
                 ON 
                 LOW 
               
               
                   
                   
               
             
          
         
       
     
         [0024]    The 1-wire signal also serves as the legacy ON INDICATOR function in in-flight entertainment system, and is capable to source up to 50 mA current at logic high level (&gt;18V) to drive an external device such as a relay or a lamp. 
         [0025]    Although only a few exemplary embodiments of the present invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. For example, the order and functionality of the steps shown in the processes may be modified in some respects without departing from the spirit of the present invention. Accordingly, all such modifications are intended to be included within the scope of this invention.