FR2731532A1 - Cable connection for transmission of music or video signals - Google Patents

Abstract

The signal transmission connection between a master unit (10) and slave peripheral units (for example mouse and keyboard (14,42)) is via a cable (26) connected through interfaces (16,20) to the master and slave units. Each interface contains a bi-directional signal transformation circuit. The signals are transformed to symmetric unidirectional signals for transmission over the cable. Each interface unit contains a circuit to transmit and to receive the line signals. A logic circuit controls operation of the transmitter and receiver in each interface so only one is operating at any instant in time. A delay circuit in the interface prevents transmission until a fixed delay after a signal has been received.

Description

CABLE LINK DEVICE FOR THE TRANSMISSION OF
SIGNALS
DESCRIPTION
Technical area
The present invention relates to a cable connection device for the transmission of signals between a central data processing unit, called "master" unit, and one or more peripheral computer units called "slave".

The invention generally applies in all areas where the master and slave units must be installed remotely from each other and in particular in the field of computer science applied to music or medicine.

State of the art
The use of computer hardware in applications requiring a quiet environment poses the problem of the removal of all elements that could create a noise nuisance for the user. A good illustration of this problem lies in the field of music computing, where, whether in a recording studio setting, or in a concert situation, the noises caused by devices such as the hard disk or the cooling fan of a computer, appear intolerable. The sound level of these devices makes it almost impossible to listen in good conditions.

 The need to control the computer equipment from where the user is located and, in this case, the place where the hearing is practiced, generally leads to the removal of the disturbing elements. This is in practice to move the central processing unit equipped with fans, hard disks, various noisy players, control elements such as keyboard, mouse, screen and other devices that are not generating noise and which must remain within the reach of the user.

 The distance of the equipment does not pose any particular problem as regards the cable transmission of video type signals between the central processing unit and the control screen. On the other hand, the cable transmission of signals between the central processing unit, the so-called "master" unit and the equipment such as the control keyboard or the mouse, for example, designated in the rest of the text by peripheral units or "slaves" ", is almost impossible when the distance exceeds typically 5 meters. The generally bidirectional signals transmitted between the master and slave units undergo, beyond this distance, alterations and deterioration by parasites which compromise the transmission of information.

 An object of the present invention is to provide a cable signal transmission device which is suitable for distances exceeding several meters and which can reach more than 100 meters.

 Another object of the present invention is to provide a transmission device that is not very sensitive to parasites.

 Yet another purpose is to provide an inexpensive device that can easily be adapted to existing computer equipment.

Presentation of the invention
To achieve these aims, the invention relates more precisely to a connection device for the transmission of signals between a central computer unit, said master unit, and at least one peripheral computer unit, called slave, the master and slave units being respectively connected to interfaces of the connecting device, and the interfaces being interconnected by cable, characterized in that each interface comprises a bidirectional signal transformation circuit respectively from the master and slave units, in unidirectional signals for their transmission by cable between the interfaces.

 Signal transmission between the master unit and the slave unit is understood to mean both the transmission of signals from the master unit to the slave unit (s) and from the slave unit (s). (s) to the master unit. By way of example, the master unit can send interrogation signals to a slave unit according to a particular protocol, for example the protocol described below, and the slave unit can respond with signals corresponding for example to commands of the user.

 Thanks to the invention, and in particular to the transformation of bidirectional signals into unidirectional signals, it is possible to transmit information over distances exceeding ten meters or so.

 The term bidirectional signal "a signal carried by an electrical connection between a master unit and a slave unit and likely to flow sometimes in the direction of the master unit to the slave unit, sometimes in the opposite direction. "Unidirectional signal" means a signal capable of propagating exclusively in one direction only, for example from the master unit to the slave unit.

 According to a particular aspect of the invention, each circuit may further comprise means for transforming the unidirectional signals into symmetrical unidirectional signals for their cable transmission between the interfaces.

 By symmetrical signal is meant a signal transmitted by means of a pair of wires carrying opposite signals in phase, an asymmetrical signal being conveyed by a single wire and being defined with respect to a reference potential.

 The symmetrical signals, even less sensitive to sources of noise surrounding the transmission line, allow transmission over distances exceeding one hundred meters.

 The transformation means comprise, for example, for this purpose a line transmitter connected upstream of pairs of transmission cables for transforming the unidirectional signals into symmetrical unidirectional signals and a line receiver connected downstream of a pair of transmission cables. to transform symmetrical unidirectional signals into unidirectional asymmetric signals.

 According to another aspect of the invention, each circuit may comprise a signal-receiving branch and a signal-transmitting branch, and means for inhibiting the transmission branch when a signal is received in the branch of signal transmission. reception.

 The inhibiting means comprise, for example, a logic circuit respectively connected to the reception branch and to a logic gate of the transmission branch for maintaining an input of said logic gate in a logic state prohibiting the transmission of a signal. transmitting the transmission branch via the logic gate, when a signal crosses the receiving branch.

 Thanks to the inhibition means, it is possible in particular to exclude any return by the transmit branch of a signal received on the receiving branch and thus avoid any risk of looping of the transmitted signals.

 Other features and advantages of the invention will emerge more clearly from the description which follows, given purely by way of illustration and without limitation, with reference to the appended drawings.

Brief description of the figures
FIG. 1 is a schematic overall view showing the connections between the device according to the invention and a computer equipment,
FIG. 2 is a functional electronic diagram of interfaces of the device of the invention,
FIG. 3 is a timing diagram showing the operation of the interfaces during a signal transmission from a master unit to a slave unit, connected by the device of the invention,
- Figure 4 is a timing diagram showing the operation of the interfaces during a signal transmission of a slave unit to a master unit, connected by the device of the invention.

Detailed Description of Modes of Implementation of the Invention
FIG. 1 illustrates an exemplary implementation in which a central processing unit 10, or CPU, equipped with noisy accessories, is connected to a keyboard 42 and to a control mouse 14 by means of a device conforming to FIG. invention. It comprises a first interface 16 connected to the processing unit 10 by means of a link 18 and a second interface 20 connected to the keyboard and to the mouse by links 22, 24. The interfaces 16 and 20 are connected between they by an electrical connection 26 which comprises two pairs of twisted son to convey symmetrical unidirectional signals as will appear later in the description. The computer equipment shown also comprises a screen 28 connected directly to the unit 10 by a conventional video link 30, i.e. a coaxial cable. As mentioned above, the video signal is such that it can be transmitted over long distances without requiring treatment in a device according to the invention.

 The electrical operation of the interfaces appears more clearly in FIG. 2, which corresponds to the simplified electronic scheme of the interfaces 16 and 20. Each of the interfaces comprises a transmission branch 32, 32 ', a reception branch 34, 34', as well as means 36, 36 'for inhibiting the transmission branch 32, 32' when a signal is received in the reception branch 34, 34 '. The inhibiting means 36, 36 'are detailed later in the description.

 Each branch 32, 32 ', 34, 34' of each interface is respectively equipped with a line transmitter 38, 38 'or a line receiver 40, 40' still referred to as "drivers". The "drivers" 38, 38 ', 40, 40' respectively make it possible to transform an asymmetrical signal of the interface into a symmetrical signal sent into the connecting cable 26 and equipped for this purpose with two pairs 42, 42 'of twisted wires. , and transform a symmetrical receive signal into an asymmetric signal.

In a simplified embodiment of the invention, the connecting cable 26, 26 'can be simply two-wire and carry an asymmetrical signal. It is thus possible to save the "drivers" 38, 38 ', 40, 40'. The points C, C 'and H,
H 'respectively interfaces 16 and 20 are then directly connected. A preferred embodiment, however, comprises a symmetrical connection as described which gives the device a better immunity to parasites.

 In each interface, before being applied to the "driver" 38, 38 ', the transmission signal passes through a NAND gate (NAND) 44, 44'. One of the inputs of the gate 44, 44 'is respectively connected to a master computer unit 10 to a terminal A, or to a slave computer unit 12 to a terminal F, via an inverting gate respectively 45, 45', while the second input is connected to the inhibiting means 36, 36 '.

 The inhibition means 36, 36 'of each interface comprise a NAND gate 46, 46' whose one of the inputs is directly connected to the output of the line receiver 40, 40 ', and whose second input is connected to the output of the line receiver via a delay line 48, 48 '.

 The delay line 48, 48 'can be understood as four gates, put into line to introduce a delay equivalent to that of four logic gates.

 The output of the NAND gate 46, 46 'is connected to the NAND gate 44, 44' via an inverting gate 50, 50 '.

The output of the inverting gate 50, 50 'allows, as shown in the timing diagrams detailed below, to maintain one of the inputs of the NAND gate 44, 44' in the logic state 0 as long as a reception signal is likely to be present respectively on the terminal
B, respectively G, that is to say on the second input of the door 44, 44 '. Thus, the output of the NAND gate 44, 44 'remains in logic state 1 throughout the duration of the reception, and whatever the signal present at the terminal B or G respectively.

 As shown in FIG. 2, the receiving branch also comprises a pair of inverters 51, 51 'and 52, 52' through which the reception signal at the output of the line receiver 40, 40 'is transmitted respectively terminals A or F, that is to say to the master unit or the slave unit (s). In the particular application described, the inverter 52, 52 'is a gate with an open collector type output.

 Due to the nature of the signals, i.e., master / slave transmission type signals, there can be no conflict between a signal from the master and a signal from the slave. It is therefore possible to transmit a signal by one of the symmetrical lines, for example C-C ', while the other line H-H' is blocked (and vice versa).

Reading the timing diagrams of Figures 3 and 4 provides a better understanding of the operation of the device during a transaction between the master unit and the slave unit. Operation is explained by referring to a particular dialogue protocol between the master unit and the slave unit (s)
It is considered that the master unit 10 is connected to the terminal A of the interface 16 and that the slave unit (s) 14, 42 is (are) connected to the terminal F of the interface 20. When the slave unit (s) has (are) no information to transmit, its (their) output (s) (terminal F) is (are) in the high state, ie the logical state 1. The master unit transmits an interrogation signal, including, inter alia, the address of a slave unit. This signal applied at A reaches
F via the components 45, 44, 38, 40 ', 51' and 52 '.

 If the slave unit concerned has no information to transmit its output (F) remains in logical state 1 for the time necessary for a possible response. After this time, the master unit queries the next slave unit and so on.

The master unit can for example interrogate sixteen potential slave units and then repeat this sequence. However, the presence of interrogation signals, received by the interface 20, prohibited by the inhibition means 36 'the passage in H, that is to say the output of the door 44', the signal coming from the slave unit (s) present in
F and G.

 When one of the slave units has to transmit information it forces its output (terminal F) to logical state 0 immediately after being interrogated by the master unit. A response time is then granted to the slave unit; this time usually ending with an end-of-message signal called "stop-bit" sent by the slave unit. The master unit can, again according to the same master / slave principle, transmit and receive data until the slave unit informs the master unit of the end of the transaction. When a signal (data) is received by the master unit (10), the NAND gate 44 of the interface 16 prohibits any passage of a signal present in B towards C.

 To facilitate the reading of the timing diagrams of FIGS. 3 and 4, the following tables I and II respectively give the relations linking the logical state of the various points A to O of the device. In addition, for the sake of simplification, the examples are given for a rectangular signal assuming that it is identical to the input and the output of the "drivers" 38, 38 ', 40, 40'. The delay introduced by each passage of the signal by a logic gate is designated At and considered to be the same regardless of the door considered, with the exception of the component 48, 48 'which corresponds to four gates.

TABLE I (signal applied in A
and received in F)

<tb><SEP> Relation <SEP> Comments
<tb> A
<tb> B = A
<tb> C = C '= BL <SEP> L = l-> C = B <SEP>
<tb> E = C
<tb> F = E
<tb> G = F
<tb> H = OG <SEP> H = l
<tb> I = H
<tb> J = H
<tb> K = JH
<tb> L = K
<tb> M = C
<tb> N = CM
<tb> O = N
<Tb>
TABLE II (signal applied in F
and received in A)

<tb> Relationship <SEP> Comments <SEP>
<tb><SEP> t = 1 <SEP>
<tb><SEP> B = A
<tb><SEP> = C '= LB <SEP> C = l
<tb><SEP> c <SEP>
<tb><SEP> F
<tb><SEP> = GO <SEP> Y = l-> H = G <SEP>
<tb><SEP> = GO <SEP> o = l-> H = G
<tb><SEP> I = H <SEP>
<tb><SEP> J = H
<tb><SEP> = JH <SEP>
<tb><SEP>; = K <SEP>
<tb><SEP> II = C
<tb><SEP> = CM
<tb><SEP> o = N
<Tb>
The timing diagram of FIG. 3 shows in a simplified way and by way of illustration that the terminal O at the output of the gate 50 is kept in the logic state "O" which prohibits any transmission of the signal via the gate 44 'when a signal, that is to say a slot in the logic state 1 in the case of the figure, is present in G, that is to say on one of the inputs of the door 44 'of the interface 20. As shown by the discontinuous dashes, the logical state "O" of the terminal O is maintained for a duration, or window of time, in which the signal present in G. is inscribed.

Similarly, as shown in the timing diagram of FIG. 4, the logical state of the terminal
L, that is to say one of the inputs of the gate 44 of the interface 16 is kept at "O" for the duration of the time when a signal is present on the other input of the gate 44, that is to say at terminal B.

 Finally, thanks to the device of the invention, it is possible to transmit signals, without risk of alteration or loop formation between a master unit and one or more slave units.

 The cable 26 which comprises the two pairs of twisted wires 42, 42 'may also have a length greater than 100 meters, that is to say sufficient to exclude disturbances due to noise from the master unit.

Claims (9)

 1. Linking device for the transmission of signals between a central computer unit (10), said master unit, and at least one peripheral computer unit (14, 42), called a slave, the master and slave units being respectively connected to interfaces (16, 20) of the connecting device, and the interfaces being interconnected by cable (26), characterized in that each interface (16, 20) comprises a transformation circuit (32, 32 ', 34, 34') bidirectional signals respectively from the master and slave units (10, 14, 42), in unidirectional signals for their cable transmission between the interfaces (16, 20).  2. Connecting device according to claim 1, characterized in that each transformation circuit further comprises means (38, 38 ', 40, 40') for transforming the unidirectional signals into symmetrical unidirectional signals for their cable transmission between the interfaces.  3. Connecting device according to claim 2, characterized in that the transformation means of each transformation circuit comprises a line transmitter (38, 38 ') connected upstream of transmission cable pairs (42, 42') for transforming the unidirectional signals into symmetrical unidirectional signals and a line receiver (40, 40 ') connected downstream of a pair of transmission cables for transforming unidirectional symmetrical signals into asymmetric unidirectional signals.  Connecting device according to claim 1 or 2, characterized in that each transformation circuit comprises a signal receiving branch (34, 34 ') and a signal transmission branch (32, 32'), and means (36, 36 ') for inhibiting the transmitting branch when a signal is received in the receiving branch.  5. Connecting device according to claim 4, characterized in that the inhibiting means (36, 36 ') comprise a logic circuit (46, 48, 50, 46', 48 ', 50') respectively connected to the branch receiving means and a logic gate (44, 44 ') of the transmitting branch for maintaining an input of said logic gate (44, 44') in a logic state prohibiting the transmission of a transmission signal of the branch transmission (34, 34 ') via the logic gate, when a signal crosses the receiving branch.  6. Connecting device according to claim 5, characterized in that the logic gate (44, 44 ') is a NAND gate (NAND).  7. Device according to claim 5, characterized in that the reception signal having a duration T, the logic circuit connected to the receiving branch comprises a delay unit (48, 48 ') to prohibit the transmission of a signal d transmission for a duration greater than the duration T of the reception signal.  8. Device according to claim 1, characterized in that the transmitting branch (34, 34 ') is connected to the respective computer unit (10, 14, 42) via a component (52, 52') having an output open collector type.  9. Device according to any one of the preceding claims, characterized in that the slave unit is selected from the group comprising the control mouse and the control keypads.