Abstract:
The present invention relates to a method of interactive communication, notably for the household applications. The method consists in realizing, on a coaxial cable, a bi-directional exchange of messages from a single primary station towards secondary stations by an individual addressing or general or limited broadcast, the initiative to transmit being managed by the primary station.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of monitoring, of control and supervision of equipment or domestic networks in the household field and has for object an interactive communication network, notably in household applications. 
     BACKGROUND OF THE INVENTION 
     Presently, there are different types of data transmission systems employing existing cabled networks or networks specifically installed for that purpose and which allow the automatic control and monitoring at a distance of certain household functions. 
     These known systems generally allow one to respond to the exigencies in the matter of monitoring and control, but exhibit a complex structure employing several individual control and monitoring modules managed by a single or several collective control modules, themselves managed by a central module. 
     SUMMARY OF THE INVENTION 
     The present invention proposes a simplification of these existing interactive systems and communication methods that they employ. 
     The object of the invention has, in effect, for object a method of interactive communication, notably in household applications, characterized in that it consists in practice, on a coaxial cable, a bi-directional exchange of messages between a single primary station and secondary stations, by an individual addressing, or by general or limited broadcast, the initiative to transmit being managed by the primary station. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     According to a characteristic of the invention, the exchanged messages between the primary station and the single or plurality of secondary stations are structured in frames of variable length. 
     Each frame is comprised of at least one &#34;header&#34; comprising a &#34;service&#34; field which determines the type of exchange, a &#34;count&#34; field for the identification of the frames and an &#34;address&#34; field designating the destination station or the transmitting station. The destination station is designated if the frame is sent by the primary station, whereas the transmitting station is designated in the case where the frame is sent by a secondary station. 
     The &#34;service&#34; and &#34;count&#34; fields are grouped in a byte and the &#34;address&#34; field comprises three bytes. 
     The bytes comprising the &#34;header&#34; fields, meaning &#34;service&#34;, &#34;count&#34; and &#34;address&#34; fields, are protected by a six-bit polynomial field, whose generating polynomial has the following formula: 
     
         x.sup.6 +x.sup.5 +x.sup.4 +x.sup.3 +1 
    
     and by a &#34;monitor&#34; field, whose value is calculated by an exclusive OR between the byte grouping the &#34;service&#34; and the &#34;count&#34; fields and the three bytes of the &#34;address&#34; field. 
     According to another characteristic of the invention, a frame may be followed, eventually, by a &#34;data&#34; field to form an information frame. The frame is then completed by a &#34;length&#34; field of one byte protected, on the one hand, by a polynomial of formula: 
     
         x.sup.6 +x.sup.5 +x.sup.4 +x.sup.3 +1 
    
     and, on the other hand, by an &#34;extension&#34; field of two bits. 
     The &#34;data&#34; field advantageously comprises between 1 and 255 bytes and is protected by a cyclical redundant 16-bit code, whose generating polynomial has the following formula: 
     
         x.sup.16 +x.sup.12 +x.sup.5 +1. 
    
     The address of a secondary station is comprised of 3 bytes decomposed into 6 nibbles of 4 bits each, each nibble being able to take any value between 00h and 0Eh, the value 0Fh being reserved to broadcast addresses. 
     The secondary stations verify the frames addressed by the primary station and the finding of an error on the &#34;length&#34; field or in the &#34;data&#34; field brings about a transmission, by the secondary station, of a negative acknowledgment frame, which is integrated in the repeat on error procedure by the primary station. 
     If an error is detected, either on one of the &#34;count&#34;, &#34;service&#34; or &#34;address&#34; fields thanks to the polynomial code, or on the &#34;monitor&#34; field, or on the &#34;length&#34; field, or on the redundant cyclical code protecting the &#34;data&#34; field, a frame is considered to be in error. A frame comprising an error on the &#34;header&#34;, meaning on one or several of the &#34;count&#34;, &#34;service&#34;, &#34;address&#34;, or &#34;monitor&#34; fields is ignored. 
     The primary station manages all of the communications. In this manner, it successively polls each of the secondary stations and detects eventual errors by supervising said secondary stations, which transmit only upon solicitation by the primary station, which is the only station that can take the initiative by an exchange. 
     The method according to the invention allows two types of addressing, an individual addressing scheme, in view of a transmission towards a single secondary station, and a broadcast addressing scheme by transmitting a same frame towards a group of secondary stations. 
     In service, the primary station transmits many types of messages, such as demands for information, of control, of inquiry, of broadcasting and of invitation to transmit. 
     In the first case, the primary station transmits an information frame and receives in return, either an information frame if the secondary station has correctly received the message, or a negative acknowledgment frame or no response if the secondary station has not correctly received the message, the primary station repeating then the attempts to transmit on the basis of a maximum number of attempts. 
     The response time of a frame is evaluated from T0 milliseconds after the transmission of the last character by the primary station. Following a predetermined T0 parameter, representing the maximum duration, the primary station determines that no response has arrived from the secondary station. In this event the primary station repeats its attempt to transmit. Attempts may be repeated until a parameter N0, representing a maximum of attempts is reached. 
     In the case of a command, the primary station transmits an information frame. The primary station receives in return, either an acknowledgment frame, if the secondary station has correctly received the frame, or a non-acknowledgment frame or no response, if the station has not correctly received the frame within a delay of T1 milliseconds after the transmission of the last character by the primary station. The transmission of an incorrectly received frame is repeated up to the maximum of N1 attempts in case of negative response. 
     To carry out an inquiry, the primary station transmits an information frame towards a group of secondary stations and receives in return, either an information frame if a single secondary station signals an event, or garbage data if many secondary stations each signal an event, the primary station then carrying out a procedure to find the secondary stations signaling an event, or no response in the case where no event has been signaled by any station after a predetermined transmission delay of T2 milliseconds. It is considered that no response has arrived if no frame has been received within said delay of T2 milliseconds after the transmission of the last character by the primary station. T2 represents a fixed parameter. 
     In the case of a broadcast, the primary station transmits N3 identical frames of information at intervals of T3 milliseconds, these frames being designed so as to not engender any response on the part of the secondary stations. 
     For the procedure of invitation to transmit, the primary station transmits a corresponding frame towards a secondary station and waits for a response, either an acknowledgment frame if the secondary station has no waiting message, or an information frame if such a message is available to the secondary station, or again no response in the case where the frame has not been correctly received by the secondary station within a delay of T6 milliseconds after the transmission of the last character by the primary station, T6 being a predetermined parameter, the primary station then carrying out a maximum of N6 attempts to repeat the transmission, N6 being as well a predetermined parameter. 
     According to another characteristic of the invention, the &#34;data&#34; field is advantageously comprised of three subfields: a mandatory &#34;type of message&#34; field of one byte, an optional &#34;object&#34; field of one byte and a &#34;parameters&#34; field, if the &#34;object&#34; field is present. 
     The &#34;type of message&#34; field contains a value indicating at least one of demand for information without parameter, of demands for information with parameter, of command without acknowledgment, of command with acknowledgment, of response to a request for information, of acknowledgment of a command, of broadcast acknowledgment, and of execution and interpretation or of impossible execution. 
     The purpose of the &#34;objects&#34; field is to contain a value indicating at least one of the following: hour, diagnostic, petition, response to petition, status, message, value, all or nothing, break, resumption, result of a broadcast command and notification of alarm. 
     The &#34;hour&#34; value is for a message transmitted by the primary station embodied by the &#34;parameters&#34; field containing 6 bytes representing respectively the date, the month, the year, the hour, the minutes and the day. 
     The &#34;diagnostic&#34; value indicates the &#34;parameters&#34; field, which corresponds to information on the signaled event, in the case of a response sent by a secondary station. 
     The &#34;petition&#34; value appears in the &#34;objects&#34; field to describe a command to execute by the primary station in the case of a response sent by a secondary station and the &#34;petition response&#34; is for a message transmitted by the primary station, and describes in the &#34;objects&#34; field the response furnished by a secondary station to a petition submitted to the primary station by an other secondary station. 
     In the case of a response sent by a secondary station, the &#34;parameters&#34; field has a byte which causes the primary station to signal the presence of a &#34;diagnostic&#34; value or a &#34;petition&#34; value or of a &#34;result of an idle command&#34; value. 
     The &#34;message&#34; value is transmitted in the form of a demand for information by the primary station and allows the primary station to recover a message from a secondary station. This value is also transmitted in the form of a command allowing the primary station to transmit a message towards one or several secondary stations. 
     The value &#34;message&#34; defined in the &#34;parameters&#34; field, is transmitted by the primary station, either in the form of a demand for information, or in the form of a command, and allows the primary station respectively, either to recover a group of numerical values from a secondary station, or to modify a group of numerical values from a secondary station. 
     The &#34;all or nothing&#34; value is transmitted by the primary station, either in the form of a demand for information, to recover the state of an entry all or nothing, from a secondary station, or in the form of a command, in view of modifying the state of a group of outputs, all or nothing. 
     The &#34;break&#34; value, defined by the &#34;parameters&#34; field, is transmitted in the form of a command by the primary station and allows the primary station to signal to a single or several secondary stations the loss of the supervision of a secondary station, which is identified by the &#34;parameters&#34; field. This &#34;parameters&#34; field also identifies the secondary station, whose resumption of supervision has been signalled to one or several secondary stations by the transmission, in the form of a command, of the &#34;resumption&#34; value. 
     The &#34;result of a broadcast signal&#34; value is transmitted in the form of a demand for information by the primary station and allows the primary station to obtain from a secondary station the result of a command whose execution has been broadcast. 
     Lastly, the &#34;notification of alarm&#34; value is transmitted in the form of a command by the primary station and allows to signal to one or several secondary stations the appearance of an alarm or of an event on a secondary station. 
     Thanks to the invention, it is possible to realize an interactive communication, notably for the household applications by employing systems of simple structure and simple methods of operation. 
     It is understood that the invention is not limited to the embodiments described. Modifications remain possible, notably in the point of view of the implementation of the method, without exceeding the scope of protection of the invention.