This invention in general relates to in-vehicle communication networks and particularly to a system and method for tunneling standard bus protocol messages through an automotive switch fabric network.
The commonly assigned U.S. patent application entitled “Vehicle Active Network,” Ser. No. 09/945,581, filed Aug. 31, 2001, Publication Number US 20030043793, the disclosure of which is hereby expressly incorporated herein by reference, introduces the concept of an active network that includes a switch fabric. The switch fabric is a web of interconnected switching devices or nodes. The switching device or nodes are joined by communication links for the transmission of data packets between the switching devices or nodes. Control devices, sensors, actuators and the like are coupled to the switch fabric, and the switch fabric facilitates communication between these coupled devices.
The coupled devices may be indicator lights, vehicle control systems, vehicle safety systems, and comfort and convenience systems. A command to actuate a device or devices may be generated by a control element coupled to the switch fabric and is communicated to the device or devices via the switch fabric nodes.
In the context of vehicular switch fabric networks, a challenge is presented in terms of connecting the switch fabric network to standard or legacy bus architectures such as the Controller Area Network (CAN) protocol, the SAE J1850 Communications Standard, the Local Interconnect Network (LIN) protocol, the FLEXRAY Communications System Standard, the Media Oriented Systems Transport or MOST Protocol, or similar bus structures. A need exists for switch fabric networks to operate seamlessly with the standard bus architectures and for switch fabric networks to handle message protocols associated with these standard bus architectures.
It is, therefore, desirable to provide a system and method to overcome or minimize most, if not all, of the preceding problems especially in the area of tunneling standard bus protocols across the nodes in an automotive switch fabric network.
While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
What is described is a system and method for tunneling standard bus protocol messages through an automotive switch fabric network. In sum, when a bus protocol message arrives on a connecting node in the network, a bus driver in the node will capture the message and store it into a message buffer where the message can be further processed by a tunneling application. The tunneling application periodically checks if there are any new bus protocol messages coming from a port connected to the bus. Each received bus protocol message will be broken, or combined, to suit the available packet size of the underlying transmit layer of the switch fabric network. Data portions such as message identification, sequence number, port number, bus data type, and data length are reserved in each data packet. If the message is being broken down, the sequence number is used to differentiate the broken segments of the bus protocol message. The bus data type is used to indicate the type of protocol data being transmitted over the switch fabric. The same tunneling application may be used to reassemble the bus protocol message at a receiving node.
Now, turning to the drawings,
The interfaces 26a-b are any suitable interface for coupling the particular vehicle device 24a-b to the network 22, and may be wire, optical, wireless or combinations thereof. The standard buses A and B may include one or more legacy communication media, i.e., legacy bus architectures such as the Controller Area Network (CAN) protocol, the SAE J1850 Communications Standard, the Local Interconnect Network (LIN) protocol, the FLEXRAY Communications System Standard, the Media Oriented Systems Transport or MOST Protocol, or similar bus structures. In this embodiment, the standard buses A and B are configured to permit communication between the network 22 and devices 24c-f.
The network 22 may include a switch fabric 28 defining a plurality of communication paths between the vehicle devices 24a-f. The communication paths permit multiple simultaneous peer-to-peer, one-to-many, many-to-many, etc. communications between the vehicle devices 24a-f. During operation of the vehicle 20, data exchanged, for example, between devices 24a and 24b may utilize any available path or paths between the vehicle devices 24a, 24b. In operation, a single path through the switch fabric 28 may carry all of a single data communication between one vehicle device 24a and another vehicle device 24b, or several communication paths may carry portions of the data communication. Subsequent communications may use the same path or other paths as dictated by the then state of the network 22. This provides reliability and speed advantages over bus architectures that provide single communication paths between devices, and hence are subject to failure with failure of the single path. Moreover, communications between other of the devices 24c, 24f may occur simultaneously using the communication paths within the switch fabric 28.
Referring to
The cooperation of the nodes 30a-h and the connection media 32 define a plurality of communication paths between the devices 24a-f that are communicatively coupled to the network 22. For example, a route 34 defines a communication path from a first node 30a to a second node 30g. If there is a disruption along the route 34 inhibiting communication of the data packets from the first node 30a to the second node 30g, for example, if one or more nodes are at capacity or have become disabled or there is a disruption in the connection media joining the nodes along route 34, a new route, illustrated as route 36, can be used. The route 36 may be dynamically generated or previously defined as a possible communication path, to ensure the communication between the first node 30a and the second node 30g.
The network 22 may comply with transmission control protocol/Internet (TCP/IP), asynchronous transfer mode (ATM), Infiniband, RapidIO, or other packet data protocols. As such, the network 22 utilizes data packets, having fixed or variable length, defined by the applicable protocol. For example, if the network 22 uses asynchronous transfer mode (ATM) communication protocol, ATM standard data cells are used.
The active portion of the data packet may represent a packet state. For example, the active portion may reflect a priority of the data packet based on aging time. That is, a packet initially generated may have a normal state, but for various reasons, is not promptly delivered. As the packet ages as it is routed through the active network, the active portion can monitor time since the data packet was generated or time when the packet is required, and change the priority of the data packet accordingly. The packet state may also represent an error state, either of the data packet or of one or more nodes of the network 22. The active portion may also be used to messenger data unrelated to the payload within the network 22, track the communication path taken by the data packet through the network 22, provide configuration information (route, timing, etc.) to nodes 30a-h of the network 22, provide functional data to one or more devices 24a-d coupled to the network 22 or provide receipt acknowledgement.
The payload portion of the data packets carries data and other information relating to the message being transmitted through the network 22. The size of the data packet (including the payload portion) will be constrained by the physical layer on which the switch fabric 28 is built. There are situations where the message size at the application layer will be larger than the packet size allowed to be transmitted over the network 22. One situation, as described in more detail below, is where standard bus protocol messages need to be transmitted through the switch fabric 28. Accordingly, in one embodiment of the present invention, a message in the application layer that is larger than the packet size of the network 22 will be broken into smaller units to fit the packet size limitation. Each unit is placed into an individual data packet and transmitted independently over the switch fabric 28 to a destination node. At the destination node, the individual data packets are reassembled to its original form and passed to the application that receives and processes the message.
Referring to
For nodes 30a, 30c, 30e, 30g that are connected to a legacy bus A, B, the node may further have a bus driver, a tunneling application, and a message buffer to store and transmit messages through the switch fabric 28. For instance, when a bus protocol message arrives on a connecting node 30a, 30c, 30e, 30g, the bus driver will capture the message and store it into the message buffer where the message can be further processed by the tunneling application. The features of the tunneling application are described in more detail below. The tunneling application periodically checks if there are any new bus protocol messages coming from the port connected to the legacy bus A, B. As will be explained further below, in one embodiment, each received bus protocol message will be broken, or combined, to suit the available packet size of the underlying transmit layer of the switch fabric network 28. Data portions such as message identification, sequence number, port number, bus data type, and data length are reserved in each data packet. If the message is being broken down, the sequence number is used to differentiate the broken segments of the legacy bus protocol message. The bus data type is used to indicate the type of bus data being transmitted over the switch fabric 28. The same tunneling application may be used to reassemble the bus protocol message at a receiving node.
To explain these features further, the embodiment of
The CAN protocol is an international standard that is based on a message oriented transmission protocol. The CAN protocol supports two message frame formats, a CAN base frame and a CAN extended frame, as will be described further below. Referring to
The control field 306 of the CAN frame message 300 contains an identifier extension bit that distinguishes between the CAN base frame and the CAN extended frame. The control field 306 of a CAN frame message 300 also contains a Data Length Code (DLC) that is used to indicate the number of following data bytes in the data field. If the message is used as a remote frame, the DLC contains the number of requested data bytes.
The data field 308 of the CAN frame message 300 is configured to hold up to 8 data bytes. After the data field 308, the CAN frame message 300 has a CRC field 310 that contains a cyclic redundant check sum. The cyclic redundant check sum allows for errors to be checked for the incoming CAN frame message 300. The acknowledge field 312 includes an acknowledge slot and an acknowledge delimiter. The acknowledge field 312 is used by a receiving device to acknowledge whether data is received correctly.
The SAE J1850 Communications Standard is an international standard that is also based on a message oriented transmission protocol. The J1850 protocol supports two systems, a 41.6 kb/s Pulse Width Modulation (PWM) scheme and a 10.4 kb/s Variable Pulse Width (VPW) scheme. The VPW will be discussed for purposes of illustrating a message under the J1850 protocol. Referring to
The data field 408 of the J1850 message 400 is configured to hold up to 8 data bytes. After the data field 408, the J1850 message 400 has a CRC field 410 that contains a cyclic redundant check sum. The cyclic redundant check sum allows for errors to be checked for the incoming J1850 message 400.
The in-frame response 412 provides a mechanism for devices that receive SAE J1850 frame messages to acknowledge receipt. A bit in the header field 304, mentioned above as an in-frame response bit, triggers the device receiving the frame message to append a reply to the end of the transmitting devices original frame message. This provides for efficient communications in that device receiving the message may respond within the same message frame as the original frame message.
The present invention allows the nodes 30a-h to be connected to different types of legacy bus protocols and tunnel the legacy bus protocol message through the switch fabric 28. The present invention advantageously allows for a modular concept and permits nodes 30a-h to be connected to a variety of bus architectures. In one embodiment of the present invention, legacy bus protocol messages (such as the CAN frame message 300 and the J1850 message 400) are tunneled through the switch fabric 28 protocol by dividing the messages into two or more separate units or data packets for transmission over the switch fabric 28. As described in
For purposes of illustrating the present invention, assume that the switch fabric 28 of
In this embodiment, as shown in
The message identification portion 260 for each of the payload portions 204a, 204b will contain a unique message identification assigned to the particular legacy bus message (for example, the CAN frame message 300 or the J1850 message 400). The message identification within the portion 260 will be the same for all payload portions 204a, 204b that are common to the same legacy bus message. The message identification is used by the nodes 30a-h to track the received data packets so that it can associated different payload portions 204a, 204b with the same legacy bus message.
The sequence portion 262 contains a sequence number associated with the payload portions 204a, 204b. The bit(s) for the sequence number portion 262 in each payload portions 204a, 204b will be different. The bits in the sequence number portions 262 are be used by the nodes 30a-h (in conjunction with the message identification) to group the received data packets so that it can re-assemble the legacy message in the correct order.
The control portion 264 contains information that identifies information pertaining to the particular legacy bus protocols and any other information that may help the data packet to route the data packet 200 to the correct destination node. For instance, the control portion 264 of the first payload portion 204a may include an identification of the tunneling protocol (TP) such as whether the received bus message relates to the Controller Area Network (CAN) protocol, the SAE J1850 Communications Standard, the Local Interconnect Network (LIN) protocol, the FLEXRAY Communications System Standard or similar bus structures. The control portion 264 of the first payload portion 204a may also include a port number (Port #) to help route the data packets 200 to the correct destination. As mentioned above in
The plurality of data elements 266-276 in the first payload portion 204a will contain any remaining portions specific to the legacy bus protocols as well as the data elements in the data fields 308, 408 of the legacy bus messages 300, 400. For instance, as shown in
On the other hand, as shown in
In a further embodiment, the present invention includes a mechanism for handling acknowledgments used in some legacy buses such the in-frame responses used in the J1850 frame message described above. Referring to
In one embodiment, the first device 24c will broadcast an original J1850 frame message over the data bus A that interconnects the first device 24c and the first node 30a (arrow 502). The J1850 frame message may have a format similar to the frame message 400 described in
An issue that may arise during the above-described tunneling operation is that the first device 24c may have set a bit in the header field 304, mentioned above as an in-frame response bit, that requires the second device 24e to reply with a response. The first node 30a may not know the correct in-frame response at the time the original frame message 400 is seen at the first node 30a. The present invention solves this issue by including an application in the first device 24c that includes a retry strategy. Additionally, the method includes configuring the first node 30a, upon receipt of the original message 300, to reply with a null or invalid response (arrow 508). The first device 24c will see the null or invalid response and initiate the retry strategy. Meanwhile, after the second device 24e receives the reassembled frame message 300, it will insert the correct in-frame response over the bus interconnecting the second device 24e to the second node 30c (arrow 512). The second node 30c will then tunnel the in-frame response via data packets to the first node 30a (arrow 514). The retry strategy includes a process that allows the first device 24c to broadcast a retry message, after a predetermined period, to the first node 30a (arrow 508). This will allow the first node 30a to then insert the correct in-frame response when it receives the retry message (arrow 516).
What has been described is a system and method for tunneling legacy bus protocols or other bus architecture data through an automotive switch fabric network. This is particular useful in transitioning traditional bus architectures to an automotive switch fabric network. In sum, when a bus protocol message arrives on a connecting node in the network, a bus driver in the node will capture the message and store it into a message buffer where the message can be further processed by a tunneling application. The tunneling application periodically checks if there are any new bus protocol messages coming from the port connected to the bus. Each received bus protocol message will be broken or combined to suit the available packet size of the underlying transmit layer of the switch fabric network. Data portions such as message identification, sequence number, port number, bus data type, and data length are reserved in each data packet. If the message is being broken down, the sequence number is used to differentiate the broken segments of the bus protocol message. The bus data type is used to indicate the type of bus data being transmitted over the switch fabric. The same tunneling application may be used to reassemble the bus protocol message at a receiving node. The above description of the present invention is intended to be exemplary only and is not intended to limit the scope of any patent issuing from this application. The present invention is intended to be limited only by the scope and spirit of the following claims.
The present application claims priority from provisional application Serial No. 60/619,232, entitled “System and Method for Tunneling Standard Bus Protocol Messages Through an Automotive Switch Fabric Network,” filed Oct. 15, 2004, which is commonly owned and incorporated herein by reference in its entirety.
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