Abstract:
An improved vehicle communications interface (VCI) is both economical and readily adaptable for running new software. The improved VCI includes a server coupled to a bank of processors. The server can communicate with a host, and the processors can communicate with different vehicle networks. Each processor includes a state machine and a media access controller for a particular vehicle network. The state machine identifies incoming messages that require real time responses and provides the requisite responses directly back to the network, without involvement of the server. Real time requirements of the server are thus relieved, allowing the server to run a non-real time, mainstream operating system for which new product software is readily available.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
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     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
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     Reference to Microfiche Appendix 
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     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to diagnostic testing of computers and computer networks in transportation vehicles, and, more particularly, to an improved device and method for communicating with an automobile&#39;s internal computer networks. 
     2. Description of Related Art 
     Modern transportation vehicles, such as automobiles, increasingly employ computer systems for managing communications, safety, and control. New automobiles typically contain 30 or 40 different computers. These computers are generally linked together to form one or more computer networks. An automobile&#39;s computers communicate over these networks via various network protocols. Different types of automobiles employ different protocols, which are generally proprietary to the automobile&#39;s manufacturer. Examples of automotive network protocols include CAN, UART, or SAE J1850. 
     Technicians require access to an automobile&#39;s computer networks to configure the automobile&#39;s computers and to run diagnostics. Access is provided via one or more access ports, which are generally located under the dashboard. The access ports are physical connectors that are accessible to a technician and provide taps into the automobile&#39;s networks. An external device can be connected to the access port. Under a technician&#39;s control, the device can be made to interact with the automobile&#39;s networks, or any of its computers, according to the respective network protocols. Diagnostic information can therefore be acquired. The device is generally programmable for configuring the automobile&#39;s computers, or for running a test program on the automobile&#39;s networks, computers, and/or the functional subassemblies that the computers control. Information about the status and operation of the automobile can be read back, analyzed, and used to indicate proper operation or to diagnose problems. 
       FIG. 1  shows a standard arrangement for testing automotive computer networks. A host device communicates with an automobile  112  via a Vehicle Communications Interface, or “VCI,”  110 . The VCI  110  has a flexible design that enables it to communicate with different types of host computing devices, such as a laptop computer  116 , a personal data assistant (PDA)  118 , or a computer workstation  128 . Other types of computing devices can be used. It can communicate with the host using different networking technologies, such as 10/100 Ethernet, IEEE 802.11 or Bluetooth. 
     The host computer (e.g., any of laptop  116 , PDA  118 , and workstation  120 ) need not be a specialized system. The host computer generally runs a mainstream operating system, such as Windows®, Linux, or PalmOS®. It generally communicates with the VCI  110  using TCP/IP, just as it does with other devices on its network or over the Internet. 
       FIG. 2  shows a block diagram of a conventional VCI  200 . The VCI  200  can be used in in the standard arrangement of  FIG. 1 . The VCI  200  includes a CPU  210 . The CPU  210  runs software for interacting with automotive networks. The CPU  210  can communicate with a host computer using a hard-wired connection (e.g., 10/100 Ethernet,  122 ), or using a wireless path (e.g., wireless LAN connection,  124 ). 
     The VCI  200  communicates with different types of automotive networks, to accommodate the configuration and diagnostic needs of various vehicles. It generally includes a number of Media Access Controllers, or “MACs.” Each MAC is a digital circuit that supports 2-way communication with a particular network protocol. For example, the VCI  200  includes a CAN MAC  220 , for communicating with CAN protocol, a UART MAC  222  for communicating with UART protocol, and a SAE J1850 MAC  224  for communicating with SAE J1850 protocol. The MACs are generally implemented as Application Specific Integrated Circuits (ASICs). A different ASIC is provided for each type of MAC. The types of MACs employed in a particular VCI  200  depends upon the types of networks the VCI communicates with. Therefore, the types of MACs may be different from those shown in  FIG. 2 , and the VCI  200  may include additional MACs. 
     The actual signals passed on an automotive network generally have voltage levels that are different from those produced or received for the respective MAC. Levels must therefore be shifted before they are sent out to the automotive network or before the MAC receives them. Physical shifters, CAN PHY  230 , UART PHY  232 , and SAE J1850 PHY  234 , accomplish the requisite level shifting for both incoming and outgoing signals. 
     A Pin MUX  240  is provided at the output of the VCI  200  to route signals to appropriate conductors of the cable  114 . This capability allows the VCI to accommodate access ports that have different pin assignments. 
     The VCI  200  sends messages out over an automotive network using generally the following process. In response to a directive from a host computer, the CPU  210  prepares a message for transmission over the automotive network. The CPU  210  sends data to the particular MAC that handles the type of automotive network to be used. For instance, if the automotive network to be used follows the CAN protocol, the CPU  210  outputs the message to the CAN MAC  220 . The CAN MAC  200  processes the data from the CPU  210  and converts it into a format that is consistent with the CAN protocol. The CAN PHY  230  adjusts the levels of the signals provided by the CAN MAC  220 , and the Pin MUX  240  routes the shifted signals to appropriate pins of the cable  114 . The VCI  200  thus manages several tasks, including data generation, data formatting, physical level shifting, and physical pin assignments for transmitted messages. 
     The VCI  200  receives messages from the automotive network using generally the reverse of the process described above. A message arrives over the cable  114 . The Pin MUX  40  routes the message to the appropriate level shifter, here CAN PHY  230 . The level shifter changes the levels of the signals carrying the message to be consistent with the voltage levels of the CAN MAC  220 . The CAN MAC  220  receives the shifted signals, which are expressed in the CAN protocol, and converts them to data, which are sent to the CPU  210 . The CPU  210  interprets the received message and takes appropriate action. This may include sending a result back to the host computer. 
     It is well known that many transactions in automotive networks require real time responses. For example, the receipt of certain messages must be acknowledged within a set amount of time to prevent an error or some other undesirable condition. In the VCI  200 , the CPU  210  has the task of generating the requisite response. The requirement to perform this task places certain constraints on the design of the CPU  210 . For example, the CPU  210  must be able to respond to incoming messages substantially in real time. This means that the CPU  210  must generally run a Real Time Operating System (RTOS). 
     RTOS&#39;s involve certain drawbacks. For example, the mainstream operating systems on the market today are not RTOS&#39;s, and software programs developed for mainstream operating systems are not readily adaptable for running on RTOS&#39;s. Consequently, software is often required to be developed and maintained specifically for an RTOS by the VCI supplier. The lack of available software for RTOS&#39;s is particularly troublesome because new host technologies are frequently introduced, such as wireless LAN and USB. Supporting these technologies with a VCI running an RTOS thus requires frequent and intensive software efforts. 
     Another problem arises if Virtual Private Network (VPN) support is needed. Typically, this support is available only for mainstream operating systems and is not available for RTOS&#39;s. 
     To overcome these drawbacks, the VCI  300  of  FIG. 3  has been proposed. The VCI  300  includes, as a component, the Conventional VCI  200  of  FIG. 2 . However, the VCI  300  also includes a VCI server  310  between the host and the Conventional VCI  200 . The VCI server  310  communicates with the Conventional VCI  200  over a network, such as Ethernet. The VCI server  310  also communicates with the host and runs a mainstream operating system, such as Windows or Linux. The VCI server  310  can thus run mainstream software for supporting new networking technologies. It can also be configured with VPN. Because the VCI server  310  is interposed between the Conventional VCI  200  and the host, the task of networking to the host is moved from the Conventional VCI  200 , where it is difficult to support, to the VCI server  310 , where support is much more convenient. Custom RTOS implementations supporting new networking technologies are thus not required. 
     Although the VCI  300  greatly reduces the effort needed to incorporate new technologies, it significantly increases the cost of the VCI. The VCI server  310  is typically a microprocessor, which, along with the requisite memory and peripherals, adds at least $100 beyond the cost of the Conventional VCI  200 . Diagnostic equipment for automobiles is highly cost sensitive, and the need for the added microprocessor reduces the appeal of an otherwise attractive solution. 
     What is needed is a VCI that provides the benefits of a mainstream operating system without the added cost. 
     BRIEF SUMMARY OF THE INVENTION 
     With the foregoing background in mind, it is an object of the invention for a vehicle communications interface to be economical and readily adaptable for use with new networking technologies. 
     To achieve the foregoing object, as well as other objectives and advantages, a vehicle communications interface includes a server coupled to a plurality of processors. Each processor includes a MAC (media access controller) for communicating with a respective vehicle network, according to a particular protocol, and a controller coupled to the MAC. The controller identifies incoming messages from the vehicle that require real time responses. It then provides these responses without the involvement of the server. Real time requirements of the vehicle communications interface are thus removed from the server, allowing the server to run a non-real time, mainstream operating system for which new technologies are readily available. Further, the MACs and controllers can be implemented at low cost, for example, using a Field Programmable Gate Array (FPGA). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional objects, advantages, and novel features of the invention will become apparent from a consideration of the ensuing description and drawings, in which— 
         FIG. 1  is a simplified drawing of a conventional system for interfacing one or more host computers with a vehicle&#39;s computer networks via a device called a Vehicle Communications Interface, or VCI; 
         FIG. 2  is a block diagram of a conventional VCI, wherein a CPU runs a Real Time Operating System (RTOS) for managing communications with the vehicle&#39;s networks; 
         FIG. 3  is a block diagram of an improved conventional VCI, wherein a VCI server is placed between the conventional VCI of  FIG. 2  and the one or more host computers of  FIG. 1 ; 
         FIG. 4  is a block diagram of a VCI according to an embodiment of the invention, wherein a plurality of processors is shown; 
         FIG. 5  is a block diagram of a generalized processor that is suitable for use in the VCI of  FIG. 4 ; 
         FIG. 6  is a flowchart showing a process according to an embodiment of the invention for transmitting messages to a vehicle network; and 
         FIG. 7  is a flowchart showing a process according to an embodiment of the invention for receiving messages from a vehicle network. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 4  shows an improved VCI  400  according to an embodiment of the invention. The improved VCI  400  includes many elements that are similar to elements of prior VCI&#39;s. For instance, the level shifters  230 - 236  and the PIN MUX  240  of  FIG. 4  are similar to the level shifters and PIN MUX shown in  FIG. 2 . Also, the VCI server  410  and memory  412  are generally similar to the VCI server  310  and memory  312  of  FIG. 3 . 
     The improved VCI  400  differs markedly from the prior art, however, in its use of processors  420 - 426 . The VCI  400  employs different processors for communicating with different types of vehicle networks. For example, CAN Processor  230  is tailored for communication via CAN protocol, UART Processor  422  is tailored for communication via UART protocol, and so forth. 
     The processors  420 - 426  are digital circuits that convey signals between the level shifters  230 - 236  and the VCI server  410 . Significantly, the processors handle time-sensitive tasks of vehicle communication on behalf of the VCI server  410 . The processors thus relieve the VCI server  410  of the need to perform these time-sensitive tasks. Consequently, the VCI server  410  can run a mainstream operating system, such as Windows or Linux, rather than an RTOS, and can easily accommodate new networking technologies, VPN, and other products. 
     The improved VCI  400  also differs markedly from prior VCI&#39;s in its use of a bus interface  416 . The bus interface  416  provides bus-level communication between the VCI server  410  and each of the processors  420 - 426 , via a bus  414 . As described in connection with  FIG. 3 , the prior art employs network-level communication with the VCI server. As is known, bus-level communication is generally faster than network-level communication. It also requires less overhead. Network-level communication, such as Ethernet, is relatively complex, and its implementation requires a great deal of processing power. By contrast, bus-level communication is usually simple and can be implemented with simple hardware. The lesser requirements of bus-level communication help to keep the performance requirements of the processors  420 - 426  low, and therefore help to implement the processors  420 - 426  at low cost. In the preferred embodiment, the bus  414  is a PCI bus, and the bus interface  416  is PCI Interface. 
     The VCI  400  has a memory  412  coupled to the VCI server  410 . The memory  412  is also coupled to the bus interface  416 . By virtue of this arrangement, processors  420 - 426  can read from and write to the memory  412  directly, without requiring any involvement of the VCI server  410 . 
       FIG. 5  shows a generic processor  500 . The processor  500  depicts in general form each of the network-specific processors  420 - 426 . Although the VCI  400  employs different processors for communicating with different types of vehicle networks, all processors have the same general form. Each processor preferably includes a Media Access Controller (MAC)  510 , a controller  512 , a timer  514 , a control register  516 , and incoming and outgoing FIFO&#39;s,  518  and  520 , respectively. 
     The MAC  510  for a particular vehicle network is preferably a standard MAC made for communicating with the vehicle network. For example, if the processor  500  is tailored for use with a CAN network, the MAC  510  is a CAN MAC, similar to the CAN MAC  220  of  FIG. 2 . 
     The controller  512  directs the operation of the processor  500 . It preferably also acts as a conduit for incoming and outgoing messages. In the preferred embodiment, a timer  514  is coupled to the controller  512  for providing a real time reference. The MAC  510  and the timer  514  can preferably interrupt the controller  512  (via IRQ lines  534  and  554 , respectively). The controller  512  can preferably interrupt the VCI server  410  (via interrupt line  536 ). 
     FIFO  518  accumulates message data received from a vehicle network in the order in which they are received. FIFO  520  accumulates message data to be sent out to the vehicle network in the order in which they are to be transmitted. 
     The control register  516  preferably contains pointers into the memory  412 . For example, one pointer indicates a location in the memory  412  where the contents of the FIFO  518  can be written. Another pointer indicates a location in the memory from which the contents of the FIFO  520  can be read. 
     As is known, the PCI bus standard, as well as others, allows devices that use the bus to be “bus masters,” temporarily granting them control over the bus. Preferably, the controller  512  is configurable as a bus master. In this mode, the controller  512  can directly read to or write from the memory  412 , via the FIFO&#39;s  418  and  420 , at the locations indicated by the control register  416 . Reading and writing of the memory  412  can thus be conducted between the controller  512  and the memory  412 , without involvement of the VCI server  410 . 
       FIG. 6  summarizes the actions taken when the VCI  400  transmits messages to a vehicle network. Beginning at step  610 , the controller  512  checks whether any messages are waiting to be sent. This step preferably entails the controller assuming bus master mode and transferring the contents of the memory  412 , at a location indicated by the control register  416 , to the FIFO  420 . 
     At step  612 , the controller  512  checks whether the FIFO  420  contains any messages. If not, the controller waits a short amount of time (step  616 ) and then checks again. It continues to check for messages indefinitely, until a message is found. 
     If any messages are found, the controller  512  proceeds to step  614 . The controller directs the passage of any received messages to the MAC  510  and directs the MAC  510  to output the message(s). The MAC  510  outputs the message(s) in the proper network protocol. From there, message(s) are passed to a level shifter (one of  230 - 236 ), to the Pin Matrix  240 , and out to the vehicle (see  FIG. 4 ). Once again, the controller  512  waits a short time (step  616 ) and then resumes checking for new messages (step  612 ). 
     Significantly, the VCI server  410  performs no real time tasks during the transmission of messages to the vehicle network. Its role is simply to deposit message data into the memory  412 . The controller  512  handles the remaining tasks. The timing of the VCI server&#39;s deposits into memory is not critical. 
       FIG. 7  shows the actions taken when the VCI  400  is receiving messages from the vehicle network. Receipt of messages differs from transmission in that receipt requires time-critical responses. The VCI controller and associated hardware handle these responses, without requiring any time critical actions on the part of the VCI server  410 . 
     Step  710  is a quiescent state, wherein the controller  512  waits to receive an incoming message from the vehicle network, via the MAC  510 . When the MAC  510  receives a message, it preferably interrupts the controller  512 . At step  712 , the controller  512  promptly retrieves the newly arrived message from the MAC  510  and analyzes the message. 
     The controller  512  preferably employs a look-up table or other storage means (not shown) to assist in analyzing the message. The look-up table lists message types, for the protocol supported by the processor, which require critical responses. It also lists the nature of the responses they require. Certain messages for certain protocols require that an acknowledgement of receipt be sent within a narrow window of time. Other messages require than an acknowledgement be sent only after a specified number of messages have been received. The look-up table preferably associates message types with the required time and/or number of messages before a response is required. 
     At step  714 , the controller determines whether the received message is of a type that requires a critical response. The controller preferably looks up the message type of the received message in the look-up table. If the message type requires a critical response, operation proceeds to step  716 . If the response is time-critical, the controller  512  programs the timer  514  in an “alarm clock” fashion, by specifying an interval of time before the response is to be delivered. When the timer  514  expires, it interrupts the controller  512 . The controller then provides the required response. Again, the response is generally in the form of a simple acknowledgement. If the response must be provided within a specified number of messages, the controller counts received messages and responds when the required count is attained. It should be appreciated that different types of vehicle networks have different requirements for responses. Some require time-critical responses, whereas others require responses within a specified number of messages. As this description is generic to all types of processors, both are discussed. It should also be appreciated that critical responses, whether they are based on time or a number of messages, are provided entirely by the controller  512  and associated hardware, without the involvement of the VCI server  410 . 
     Regardless of whether a critical response is required, operation next proceeds to step  718 , whereupon the controller  512  pushes the received message onto the FIFO  518 . 
     For many protocols, messages form parts of larger communication structures called transactions. For instance, a “message” in CAN protocol is 8 bytes long, whereas a “transaction” is defined as a 4K block of messages. In addition, certain protocols indicate whether an error has occurred during the exchange of a message in a field within the message itself. Preferably, the controller  512  counts the messages received and thus can determine whether a transaction is complete. It can also preferably determine whether an incoming message indicates that an error has occurred. 
     At step  720 , the controller  512  checks whether the newly received message completes a transaction. It also checks whether an error has occurred. If either of these conditions is true, operation proceeds to step  722 . There, the controller  512  uploads the contents of the FIFO  518  to the memory  412 . In performing this step, the controller  512  preferably assumes bus master mode. The contents of the FIFO  518  are written directly to the memory  412 , at the location specified in the control register  516 . This step preferably occurs without the intervention of the VCI server  410 . 
     Because completed transactions and errors typically require a response, eventually, the controller  512  interrupts the VCI server  410  at step  724 . The VCI server  410  responds generally by reading the uploaded messages from the memory  414  and taking appropriate action. The response of the VCI server  410  to the interrupt is not time-critical. Upon completion of step  724 , operation resumes at step  710 , whereupon the controller  512  waits to receive another message. 
     If the newly received message does not mark the end of a transaction or indicate an error (at step  720 ), the controller proceeds to step  728  to check whether the FIFO  518  is full. If the FIFO is full (i.e., has reached its storage capacity), the controller uploads the contents of the FIFO  518  to the memory (step  730 ), using the same process described in connection with step  722  above. Once the messages are uploaded, the controller once again assumes a wait state, as shown in step  710 . 
     Having described both transmitting and receiving network exchanges, it is apparent that the processor  500  handles all real time activities associated with vehicle network communication, and that the VCI server  410  performs no real time activities. Therefore, the VCI server  410  is not required to run an RTOS and is free to run any operating system the VCI manufacturer chooses to use. 
     The VCI server  410  still plays a role in vehicle network communications, however. For example, the VCI server  410  prepares network messages to be sent to the processors  500 . It also reads back messages that are received. To perform these functions, the VCI server  410  preferably runs a software program called a “driver.” The driver includes functions for sending and receiving messages to and from the various processors  500 . 
     In the preferred embodiment, the driver also includes one or more functions for initializing the processors  500 . The initialization functions preferably download configuration data to each processor  500  over the bus  414 . The PCI bus supports memory mapped access to devices on the bus. The initialization function preferably uses this memory mapped mode to configure each processor. 
     The tasks required of the controller  512  can be performed with relatively simple hardware. Preferably, the controller  512  is a state machine. Although the processes for transmitting and receiving messages are shown in two separate flow charts, those skilled in the art of digital circuit design can readily implement both processes in a single state machine. Alternatively, two state machines may be used: one for transmitting messages and one for receiving messages. 
     The controller  512  is preferably implemented with an 8-bit microprocessor. Although an 8-bit microprocessor has more capability than the tasks of the controller  512  require, it is simple to implement and can be provided at low cost. 
     A significant advantage of the VCI  400  is its ability to be made at low cost. The bus interface  416  and processors  420 - 426 , including their respective MAC&#39;s  510  and support circuitry, can be realized together on a single FPGA. Each of these components is commercially available as a program description, which can be licensed and downloaded from the manufacturer for inclusion in an FPGA. To reduce cost even further, the VCI server  410  and memory  414  can also be embedded in the FPGA, or provided in an additional FPGA. 
     Another advantage of the VCI  400  is its flexibility. FPGAs can be reconfigured, even in the field, simply by downloading new configuration data. New hardware configurations can be stored in the VCI software driver. Therefore, upgrading the VCI hardware is accomplished simply by upgrading the driver. 
     Having described one embodiment, numerous alternative embodiments or variations can be made. For example, as described herein, the VCI  400  communicates with a host computer, such as a laptop, workstation, or PDA. This is not strictly required, however. Alternatively, the VCI  400  can be run as a stand-alone device, with the VCI server  410  managing the tasks previously allocated to the host. According to one variation, the VCI server  410  is itself a laptop computer, workstation, PDA, or the like. The other components of the VCI  400  (bus interface, processors, shifters, and pin mux) are provided on a card or module that plugs into the VCI server  410  and accesses its bus. 
     The improved VCI has been shown and described for use with automobiles. However, it can readily be used with any transportation vehicle that includes computer networks. 
     Therefore, while the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.