Abstract:
A process for transmitting asynchronous data packets includes a step of starting a packeting operation. After receiving a message from a message composition module, the process interrupts the packeting operation based on the message. A packet formed during the packeting operation prior to the interrupting step is transmitted. The steps are repeated so as to transmit a plurality of packets.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation application of published U.S. application Ser. No. 09/988,527, filed Nov. 20, 2001, which claims priority under 35 U.S.C. § 119 to French Patent Application 00 16146, filed on Dec. 12, 2000, the entire disclosure of both of which are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention concerns a process and device for deterministic transmission of asynchronous data in packets.  
           [0004]    2. Discussion of the Background  
           [0005]    In devices of the prior art for deterministic transmission of asynchronous data in packets, the acquisition device and data acquired by this device are asynchronous. Data packeting is made according to an inherent sequencing. A packet corresponds to one or several acquired data processed with or without wrapping, the wrapping being made up of a heading and an end. The number of data transmitted in the output message corresponding to a packet is defined according to two criteria:  
           [0006]    the number of data is restricted:  
           [0007]    it is always the same, or  
           [0008]    the maximum is specified  
           [0009]    the distribution of data is positioned temporally in an equally-timed manner or not.  
           [0010]    In the first example of data transmission from a packet i in the output message, as illustrated in FIG. 1, the number of data Mi is always the same, and distributed in an equally-timed manner (Ti equal delays).  
           [0011]    In the second example of data transmission from a packet i in the output message, as illustrated in FIG. 2, the maximum number of data Mi is always the same, it is MxTxi over an identified period of time Txi, and distributed unequally-timed (Txi variable delays)—MxTxi varies at each Txi, with MxTxi≦Mi.  
           [0012]    In the field of data acquisition and telemetry of flight testing installations, the numerical or digital data, conveyed on continuous and cyclic messages, issued by acquisition and processing systems of the prior art is stored in the FIFO (First in-First out) batteries as and when it arrives. The data arrives in a totally asynchronous manner.  
           [0013]    A module for packeting facilitates placing certain data from these FIFO batteries according to a predefined order. It also facilitates enhancing this data with elements of the relative date calculation type, data identification, and formatting of data, etc. A packet thus obtained is therefore a group of data with a precise format and containing data in a precise order.  
           [0014]    A module for packeting operates according to the following succession of stages:  
           [0015]    1) reception of data contained in the FIFO batteries (dump),  
           [0016]    2) start of packeting,  
           [0017]    3) packeting, with sorting and data enhancement,  
           [0018]    4) end of packeting,  
           [0019]    5) sending of the packet to a message composition module.  
           [0020]    This message composition module recovers, one after the other, the packets created by the packeting modules. A message is then made up of successive packets in a predefined order.  
           [0021]    A formatting module then facilitates setting the message in electrical format in the protocol used for the transmission.  
           [0022]    The operating cycle of the packeting module is self-sustaining. When the message composition module needs a packet, it sends a request to the packeting module which transmits the packet if it is made up, i.e. if stage 4 is finished. If not, it sends nothing or else an empty packet so as not to block the message composition module. The data is transmitted via the various stages 1 to 5—the data arrives, it is put into packets by a self-sustaining device which has its own life, as it is only transferred in the message if the packet is ready. The message can contain no data, solely because the packeting has not been finished.  
           [0023]    In these devices of the prior art, the data conveyed on the messages is at fixed slots in time. They are PCM (Pulse Coded Modulation) type messages which meet the IRIG106 standard. The formalism of packeting, as a packet can be made up of one datum, is standardized. On the other hand, this standard stipulates nothing on the transmission time of the packets. It is the same for the CE83 and CCSDS standards.  
           [0024]    As illustrated in FIG. 3, the data and transmission in the output message are asynchronous, the transmission time TT therefore varies between the time of packeting TP and a duration 2*TP equal to twice this time, as the transmission time in the output message TMS is such that TMS&lt;&lt;TP.  
         SUMMARY OF THE INVENTION  
         [0025]    The aim of the invention is to mitigate the disadvantages of devices of the prior art, by enabling:  
           [0026]    transmission of the maximum amount of data in the output message,  
           [0027]    controlling transmission time of the acquired data,  
           [0028]    having the greatest possible ratio for the number of acquired/wrapped data in the packet.  
           [0029]    The invention concerns a process of deterministic transmission of asychronous data in packets, in which data arriving asynchonously is stored in batteries as and when it arrives.  
           [0030]    The process can include the following stages:  
           [0031]    reception of data contained in a set of batteries in one of several packeting modules, start of packeting, packeting with sorting and enhancement of data, end of packeting and sending of the packet made up,  
           [0032]    stoppage of the packet make-up in the course of realization in a packeting module when a message composition module needs this packet, transmission of the packet thus made up, start of the realization cycle of a new packet,  
           [0033]    recovery, one after another, of packets thus created in a predefined order in the message composition module,  
           [0034]    setting the message, compiled in the message composition module, in the electrical format in the protocol used for the transmission.  
           [0035]    In this process, a packeting module which is no longer self-sustained is used.  
           [0036]    In this process, as soon as the message composition module requests a packet, it receives the latter for it is this module that controls the packeting cycle.  
           [0037]    Contrary to devices of the prior art in which the messages are only compiled with “well finished” packets (with the risk of having empty packets), in the process of the invention each message carries packets perhaps “less well finished” but all the data which can be, is transmitted as soon as transmission is requested. The timing cycle of datum between input and output of a device implementing this process is therefore controlled.  
           [0038]    The invention also concerns a device of deterministic transmission of asynchronous data in packets including:  
           [0039]    at the least one input module receiving the input data,  
           [0040]    batteries receiving numerical data stemming from this input module,  
           [0041]    several packeting modules each connected to at least one battery,  
           [0042]    at the least one control module for battery dump monitored by at least one packeting module,  
           [0043]    a message composition module receiving the outputs of all the packeting modules, which can send an order of end of packet make-up to each one,  
           [0044]    a module for formatting packets,  
           [0045]    an output module capable of issuing each made-up packet on a transmission line.  
           [0046]    The process and the device of the invention can be used notably in data acquisition and real-time processing systems for test installations for new aeroplanes. The solution proposed in the invention for such systems offers the following advantages. To follow vibration (or flutter) tests which are very dangerous for a plane, it is essential to perfectly control the transmission time TT, as the useful acquired data must be given to a specialist with a delay TT either less than 100 ms, or parameterized depending on the type of test. With the solution stipulated in the invention TT=TP, while in the devices of prior art TP&lt;TT&lt;≅2*TP on the assumption that TMS&lt;&lt;TP. The objectives are therefore optimized with the solution of the invention. In fact, at fixed TT, TP is greater with the recommended solution than with the solution of devices of the prior art. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0047]    [0047]FIGS. 1 and 2 illustrate two examples of transmission of data from a packet, in a device of the prior art.  
         [0048]    [0048]FIG. 3 illustrates an example of operation of a device of the prior art.  
         [0049]    [0049]FIG. 4 illustrates the operation of the process of the invention.  
         [0050]    [0050]FIG. 5 illustrates the device of the invention.  
         [0051]    [0051]FIG. 6 illustrates an example of operation of the device of the invention illustrated in FIG. 5.  
         [0052]    [0052]FIGS. 7 and 8 illustrate an example of realization for an acquisition of arinc429 bus using respectively a device of the prior art and the device of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0053]    The process of deterministic transmission of asynchronous data in packets of the invention in which data arriving asynchronously is stored in FIFO batteries as and when it arrives, includes the following stages:  
         [0054]    reception of data contained in the batteries,  
         [0055]    start of packeting,  
         [0056]    packeting with sorting and enhancement of data,  
         [0057]    end of packeting,  
         [0058]    sending of the packet to a message composition module which recovers the packets created one after another, in a predefined order,  
         [0059]    and, when this message composition module needs a packet:  
         [0060]    stoppage of make-up of the packet in the course of realization,  
         [0061]    transmission of the packet thus made up,  
         [0062]    start of the realization cycle of a new packet.  
         [0063]    As illustrated in FIG. 4, the process of the invention consists in synchronizing the start and end of packet make-up in relation to their transmission in the output message—TMS being the transmission time in the output message, TP the packeting time and TT the transmission time with TT=TP+TMS. The solution obtained with TP&gt;&gt;TMS advantageously meets the previously specified objectives.  
         [0064]    For an identified packet, the packeting limits the number of acquired data to a FIG. x. If during the time TP, there are x+m data to be packeted, m data is then lost.  
         [0065]    The device of the invention, illustrated in FIG. 5, includes:  
         [0066]    at the least, one input module  10  receiving input data, for example a digital bus BN and analog data DA,  
         [0067]    at the least a set of batteries  11  receiving digital data coming from this input module, possibly through an analog/digital converter  12 , connected to at least one packeting module  13 ,  
         [0068]    at the least one control module for battery dump  14  monitored by at least one packeting module  13 ,  
         [0069]    a message composition module  15  receiving the outputs of all the packeting modules  13 , which can send an order of end of packet make-up to each one,  
         [0070]    a module for formatting packets  16 ,  
         [0071]    an output module  17  capable of issuing each made-up packet on a transmission line  18 .  
         [0072]    In the device of the invention, the digital or digitized data is stored in the FIFO batteries  11  as and when it arrives. The data arrives in a totally asynchronous manner—seen from the device its arrival is random.  
         [0073]    The role of each packeting module  13  is to place certain data from the batteries  11  according to a predefined order. It can also enhance this data with elements of the relative date calculation type, data identification and formatting of the data. A packet is therefore a group of data with a precise format and containing data in a precise order.  
         [0074]    As described previously, each packeting module  13  operates according to the following cycle:  
         [0075]    1) reception of the data contained in the batteries,  
         [0076]    2) start of the packeting,  
         [0077]    3) packeting with sorting and enhancement of the data,  
         [0078]    4) end of the packeting,  
         [0079]    5) sending of the packet to the message composition module.  
         [0080]    What differentiates the device of the invention from devices of the prior art is the way in which each task 1 to 5 is triggered.  
         [0081]    The message composition module  15  recovers the packets created by the successive packeting modules  13  one after the other in a predefined order.  
         [0082]    The operating cycle of this module  13  is not self-sustaining. When the message composition module  15  needs a packet, it sends the request. This stops make-up of the packet in the course of realization. It transmits the packet thus made up then starts the realization cycle of a new packet.  
         [0083]    The formatting module  16  is responsible for setting the message  15  in electrical format in the protocol used for the transmission (recognised function and realization).  
         [0084]    In an example of operation, the device of the invention includes three packeting modules  13 . The make-up of packets that they generate (P 1 , P 2  and P 3  respectively) is unimportant (data sorting, enhancing, etc.). As illustrated in FIG. 6, a message is made up of the succession of three packets—P 1  followed by P 2  followed by P 3 —which are transmitted by the message composition module  15  to the formatting module  16 , TP being the packeting time. In this example wrapping elements are not taken into consideration (start of frame, end of frame, checksum, etc.) realized by the formatting module  16 .  
         [0085]    At present an example of realization will be considered which is an acquisition of arinc429 bus on the assumption that TMS&lt;&lt;TP, TCB being the bus cycle time, the number of data always being the same, and distributed in an equally-timed manner:  
         [0086]    [0086]FIG. 7 illustrates operation of a device of the prior art,  
         [0087]    [0087]FIG. 8 illustrates operation of the device of the invention as described above.  
         [0088]    The advantages of the solution proposed by the invention as compared with devices of the prior art are shown in Table 1 at the end of the description. The device of the invention meets the objectives defined previously and reveals a very significant gain as compared with the devices of the prior art.  
                                                         TABLE 1                                               Device of                       the prior art-                       Device of the                       invention/           Output message   Device   Device   Device of the           for the time   of the   of the   invention =&gt;           window TT   prior art   invention   gain                                        Number of   18   11   64%           data           Number of   2   1   100%            wrappings