Patent Publication Number: US-2003229472-A1

Title: Field maintenance tool with improved device description communication and storage

Description:
[0001] This application is a continuation-in-part application of U.S. patent application Ser. No. 10/310,703, filed Dec. 5, 2002 and entitled “INTRINSICALLY SAFE FIELD MAINTENANCE TOOL”, which claims the benefit of U.S. provisional patent application Ser. No. 60/338,477, filed Dec. 6, 2001, entitled “INTRINSICALLY SAFE FIELD MAINTENANCE TOOL.” 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] Intrinsically safe field maintenance tools are known. Such tools are highly useful in the process control and measurement industry to allow technicians to conveniently communicate with and/or interrogate field devices in a given process installation. Examples of such process installations include petroleum, pharmaceutical, chemical, pulp and other processing installations. In such installations, the process control and measurement network may include tens or even hundreds of various field devices which periodically require maintenance to ensure that such devices are functioning properly and/or calibrated. Moreover, when one or more errors in the process control and measurement installation is detected, the use of an intrinsically safe handheld field maintenance tool allows technicians to quickly diagnose such errors in the field.  
       [0003] One such device is sold under the trade designation Model 275 HART Communicator available from Rosemount Inc., of Eden Prairie, Minn. The Model 275 provides a host of important functions and capabilities and generally allows highly effective field maintenance. However, the Model 275 does not currently support, communication with non-HART (Highway Addressable Remote Transducer) devices.  
       [0004] The HART protocol has a hybrid physical layer consisting of digital communication signals superimposed on the standard 4-20 mA analog signal. The data transmission rate is approximately 1.2 Kbits/SEC. HART communication is one of the primary communication protocols in process industries.  
       [0005] Another major process industry communication protocol is known as the FOUNDATION™ fieldbus communication protocol. This protocol is based on an ISA standard (ISA-S50.01-1992, promulgated by the Instrument Society of America in 1992). A practical implementation was specified by the fieldbus foundation (FF). FOUNDATION™ fieldbus is an all-digital communication protocol with a transmission rate of approximately 31.25 Kbits/SEC.  
       [0006] In the past, in order to provide a handheld communicator, such as the Model 275, with the requisite information to interact with the various field devices with which it may be coupled, the Device Descriptions of such devices were compiled from one or more Device Description sources into a single relatively large Device Description binary file. The size of this Device Description binary file was generally limited to a little over 11 megabytes in size due to addressing constraints imposed by prior art processors. The binary file itself was uploaded from an external source into the handheld communicator to enable the handheld communicator to interact with the required process devices. In the event that any changes were desired to be made to the Device Descriptions, the entire Device Description binary would need to be recompiled and uploaded. This method, while proving satisfactory in the past, creates drawbacks for modern intrinsically safe field maintenance tools. These drawbacks will be illustrated later in the Specification as embodiments of the present invention are explained.  
       SUMMARY OF THE INVENTION  
       [0007] Improved methods for transferring Device Description data to handheld field maintenance tools are provided. Aspects of the invention include transmitting the Device Description information wirelessly, such as through an infrared data access port, to the handheld field maintenance tool. Embodiments of the invention also include storing and maintaining two or more Device Description binary files within the handheld field maintenance tool. In this manner, updates can be transferred to the handheld field maintenance device, preferably wirelessly, in significantly less time than would be required if all Device Description binary information were in a single file. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0008]FIG. 1 illustrates a multi-drop wiring configuration.  
     [0009]FIGS. 2A and 2B illustrate ways in which an intrinsically safe field maintenance tool may be connected to a process device.  
     [0010]FIG. 3 is a diagrammatic view of field maintenance tool in accordance with an embodiment of the present invention.  
     [0011]FIG. 4 is a diagrammatic view of Device Description binary file generation.  
     [0012]FIGS. 5A and 5B illustrate Device Description binary file generation and maintenance in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0013] An improved field maintenance tool is used to maintain both two-wire and four-wire (i.e. external power) field devices using one or more process measurement and control protocols. Preferably, both configuration and calibration are supported via DDL technology. DDL technology is generally known and additional reading regarding Device Description Language can be found in U.S. Pat. No. 5,960,214 to Sharp, Jr. et al.  
     [0014]FIG. 1 illustrates an exemplary system in which embodiments of the present invention are useful. System  10  includes controller  12 , I/O and control sub-system  14 , intrinsic safety (IS) barrier  16 , process communication loop  18  and field devices  20 . Controller  12  is coupled to I/O and control sub-system  14  via link  21  which can be any suitable link such as a local area network (LAN) operating in accordance with Ethernet signaling protocols or any other suitable protocol. I/O and control sub-system  14  is coupled to intrinsic safety barrier  16  which in turn is coupled to process communication loop  18  to allow data communication between loop  18  and I/O and control sub-system  14  in a manner that limits energy passing therethrough.  
     [0015] In this illustration, process communication or process control loop  18  is a FOUNDATION™ fieldbus process communication loop and is coupled to field devices  20 , which are shown coupled arranged in a multi-drop configuration. An alternative process communication loop (not shown) is an HART® process communication loop. FIG. 1 illustrates a multi-drop wiring configuration that vastly simplifies system wiring compared to other topologies such as the star topology. Multi-drop HART® configurations support a maximum of 15 devices, while multi-drop FOUNDATION™ Fieldbus configurations support a maximum of 32 devices.  
     [0016] Intrinsically safe field maintenance tool  22  is coupled to loop  18  as illustrated in FIG. 1. When coupled to a process control loop as shown, device  22  can perform a number of the communication and diagnostic functions. Device  22  can couple to and interact with HART process communication loops in much the same way the presently available HART Model 275 Communicator can.  
     [0017]FIG. 2A illustrates device  22  coupled to HART-compatible device  20  via terminals  24 . Alternately, device  22  can communicate with other devices on the process instrumentation communication loop, such as device  24  via the loop itself, as indicated in FIG. 2B.  
     [0018]FIG. 3 is a diagrammatic view of field maintenance tool  22  in accordance with embodiments of the present invention. As illustrated, device  22  preferably includes three communication terminals  26 ,  28  and  30  which facilitate coupling device  22  to process communication loops and/or devices in accordance with at least two different process industry standard protocols. For example, when device  22  is to be coupled to a loop of a first process industry standard protocol, such coupling is effected using terminal  26  and common terminal  28 . Accordingly, the connection then is made via media access unit  32  which is configured to interact upon the process communication loop in accordance with the first industry standard protocol. Additionally, when device  22  is to be coupled to a process and control measurement loop that operates in accordance with a second industry standard protocol, such connection is made via common terminal  28  and terminal  30 . Thus, the connection is effected via the second media access unit  34  which is configured to interact upon the process communication loop in accordance with the second industry standard protocol. Both media access units  32  and  34  are coupled to processor  36  which receives data from one of the media access units and interprets that data accordingly.  
     [0019] In accordance with embodiments of the present invention, device  22  includes additional hardware enhancements that facilitate increased functionality over that generally available in the prior art. Specifically, device  22  includes infrared data access port  42  which is coupled to processor  36  to allow device  22  to transfer information to and from a separate device using infrared wireless communication. One advantageous use of port  42  is for transferring and/or updating Device Descriptions stored in one or more memories of device  22 . Thus, the separate device such as computer  12 , can obtain a new Device Description from floppy disk, CD ROM, or the internet and wirelessly transfer the new Device Description to device  22 .  
     [0020] Processor  36  is preferably a commercially available microprocessor such as those found in modern handheld computing products. One example of such a processor is available from Texas Instruments under the trade designation OMAP1510 which is currently available in the model Tungsten handheld computing device from Palm. Processor  36  differs from prior processors in intrinsically safe field maintenance tools in a number of respects. One difference is that processor  36  supports a substantially larger addressable memory space. Embodiments of the present invention preferably employ memory capacities that substantially exceed that of the prior art. For example, random access memory modules of handheld intrinsically safe field maintenance tools in accordance with embodiments of the present invention can be 512 megabytes or more. This allows substantially more memory capacity for applications, program and/or device data, as well as Device Descriptions.  
     [0021] Embodiments of the present invention also include a method and system that facilitate the fast and efficient interchange of Device Description information. Further, embodiments of the present invention are practicable with both custom-designed handheld field maintenance tools as well as commercially available handheld computing devices. One feature of such devices is infrared data access port  42 . As set forth above, the provision of port  42  facilitates wireless infrared communication with the handheld field maintenance tool. This communication preferably includes Device Description information. However, communication through port  42  can be used to transfer any suitable data, such as field device configuration data, simple text files, handheld tool-specific applications and/or other applications. Infrared communication using port  42  allows the handheld field maintenance tool to send and receive information from any device that has another suitable infrared transceiver. Such devices can include desktop computers, mobile computing devices, or other intrinsically safe handheld field maintenance tools. For example, two such intrinsically safe field maintenance tools can be physically placed in such a way that their respective infrared ports are aligned. Then, each tool is placed into a special mode where they communicate via ports  42  with one another. In this case, one such handheld tool is chosen by the technician as the master unit, from which the technician then initiates tool-to-tool communication.  
     [0022] This information sharing among intrinsically safe field maintenance tools is facilitated with an application set composed of compiled code executing on each tool. Utilizing the combination of the application set and native operating system support for the infrared port, the tools communication applications communicate with each other to resolve compatibility issues and determine which information, if any, can be shared between them. The master unit (the one which initiated the infrared communication) will then allow the technician to choose which of the available information should be shared between the tools. The field maintenance tools will then transfer the information back and forth via infrared ports  42  as necessary to satisfy the technician&#39;s request.  
     [0023] Data access speeds of current commercially available infrared data access ports, such as port  42 , are relatively limited. For example, currently infrared data access port  42  has a data access speed of approximately 6 kilobytes per second. This data access speed can create undesirable delays when uploading binary Device Description information. For example, the single 11 megabyte Device Description binary file used in the prior art would require over 30 minutes to pass through data access port  42  at a 6 kilobyte per second data access speed. This limitation becomes more pronounced as the substantially larger memory capacity of the handheld field maintenance tool is used to contain ever larger Device Description binaries. Given that technician time is extremely valuable, it is important that the amount of time that that technician must wait for Device Description information to upload from a computer, or another handheld device via wireless data access port  42  be minimized.  
     [0024] In the past, ROM-based memory solutions were employed to move updated Device Descriptions for field devices developed after the release data of the handheld field maintenance tool to the tool. The problem with ROM-based memory solutions was that they require programming and often the handheld tool cannot program (burn or otherwise affect) the ROM itself. This makes it impossible to update the tool with newly developed Device Descriptions without the addition of a ROM programming function, and the cost associated therewith.  
     [0025] In accordance with an embodiment of the present invention, a solution is achieved by using the application set, composed of complied code executing on each of the computing devices, to effect the transfer. Preferably, the operating system of the handheld field maintenance tool provides intrinsic support for data access port  42  and the communication applications then communicate with each other to arbitrate compatibility issues and subsequently update the handheld field maintenance tool with newly developed Device Descriptions for field devices. Preferably, this process is enhanced in such a way that such updates and/or additions can be effected with a relative minimum of upload time. Accordingly, the practice of the prior art encoding all of the Device Descriptions into a single large binary file is discarded. Instead, a plurality of stand-alone Device Description binary files are maintained within the handheld field maintenance tool. Thus, instead of having to transfer a file in excess of 11 megabytes through the rate-limited data access port  42 , a stand-alone Device Description binary is directed solely to the update and can be transferred in substantially less time. For example, a typical stand-alone Device Description binary in accordance with embodiments of the present invention is on the order of approximately 200-300 kilobytes. These files are transferable through data access port  42  in less than 1 minute. Moreover, as the total number of updates or data related to Device Descriptions increases, the number of the individual Device Description binaries resident within the handheld device increases, while the time required to affect such updates does not. Thus, for example, if the total size of all Device Description binaries were to grow to say 20 megabytes, the update time would still be approximately less than 1 minute since a stand-alone Device Description binary update file is all that is required for an update. In contrast, the prior art approach to updating Device Description information would require almost 60 minutes thus rendering such updates increasingly undesirable as time goes on.  
     [0026]FIG. 4 is an illustration of the process of creating a Device Description binary image file. Individual Device Description source files  50 ,  52 ,  54  are provided along with common information  56  to a software module known in the art as a linker  60  which functions essentially as a compiler. Linker  60  generates as an output a single Device Description binary image file  62  which is then uploaded to handheld device  64 . Thus, in the prior art, each handheld device contained a single Device Description binary image file.  
     [0027]FIG. 5A illustrates a process of creating a stand-alone Device Description binary file. Exemplary DD source file  70  and common information  72  are provided to linker module  60  much in the same manner as set forth above with respect to FIG. 4. Linker  60  generates Device Description stand-alone binary file  74 . The term “stand-alone” indicates that the Device Description binary file is complete in and of itself in that all common information required for use of the Device Description is provided within the file. Note, more than one Device Description source file can be provided to the linker such that a given stand-alone binary file may include binary Device Description data with respect to more than one Device Description. In such case, the generation of binary Device Description data illustrated with respect to FIG. 5A is exactly the same as illustrated with respect to FIG. 4. However, a significant distinction between embodiments of the present invention and the prior art is illustrated with respect to FIG. 5B.  
     [0028]FIG. 5B illustrates handheld tool  64  including memory  76  which may comprise, for example, removable memory module  44  and/or expansion memory module  48  (described in greater detail below). The plurality of Device Description binary files are conveyed, preferably via infrared data access port  42 , to memory  76  from an external device such as a desktop computer, a mobile computing device, or another field maintenance tool. Memory  76  also includes one or more data structures, or overhead  79 , that maintain pointers, or other indications to each stand-alone Device Description binary file,  80  and  82 . Preferably, each stand-alone binary Device Description file includes a unique identifier for the field device to which it is directed as well as the version number of the Device Description. Thus, if an update is issued by a given device manufacturer for a specific field device, that single Device Description can be compiled with a linker and uploaded to the handheld field maintenance tool. Preferably, handheld field maintenance tool  64  includes suitable software that identifies, or otherwise recognizes, a later revision number for an already existing Device Description and overwrites the existing Device Description with the new Device Description. In the event that the old stand-alone Device Description cannot be overwritten, (for example if the obsolete Device Description includes one or more other Device Descriptions that are not outdated) a record is generated to ensure that when a field device that is the subject of the update is encountered that the updated Device Description is used. One way to accomplish this is by using a table correlating field devices with stand-alone binary Device Descriptions.  
     [0029] The following description provides details of the memory modules  42  and  44  of device  22  in accordance with embodiments of the present invention. Removable memory module  44  is removably coupled to processor  36  via port/interface  46 . Removable memory module  44  is adapted to store software applications that can be executed instead of primary applications on processor  36 . For example, module  44  may contain applications that use the HART or FOUNDATION™ fieldbus communication port, for example, to provide a comprehensive diagnostic for a given process device. Additionally, module  44  may store software applications that aid in the calibration or configuration of specific devices. Module  44  may also store a software image for a new or updated primary device application that can subsequently be flashed into the memory of device  36  to enable execution of the updated application. Further still, module  44  provides removable memory storage for the configuration of the device allowing a field maintenance technician to acquire a relatively substantial amount of device data and conveniently store such data for transfer to another device by simply removing module  44 .  
     [0030] Preferably, module  44  is adapted to be replaceable in hazardous areas in a process plant. Thus, it is preferred that module  44  comply with intrinsic safety requirements set forth in: APPROVAL STANDARD INTRINSICALLY SAFE APPARATUS AND ASSOCIATED APPARATUS FOR USE IN CLASS I, II AND III, DIVISION 1 HAZARDOUS (CLASSIFIED) LOCATIONS, CLASS NUMBER 3610, promulgated by Factory Mutual Research October, 1988. Examples of specific structural adaptations for memory module  44  and/or interface  46  to facilitate compliance include specifying the operating voltage level of memory module  44  to be sufficiently low that stored energy within module  44  cannot generate a source of ignition. Additionally, module  44  may include current limiting circuitry to ensure that in the event that specific terminals on module  44  are shorted, that the discharge energy is sufficiently low that ignition is inhibited. Finally, interface  44  may include physical characteristics that are specifically designed to prevent exposure of electrical contacts on memory module  44  to an external environment while simultaneously allowing suitable interface contacts to make electrical contact with module  44 . For example, module  44  may include an over-modeling that can be pierced or otherwise displaced by coupling module  44  to interface  46 .  
     [0031] Device  22  also preferably includes expansion memory module  48  coupled to processor  36  via connector  50  which is preferably disposed on the main board of device  22 . Expansion memory module  48  may contain Device Descriptions of first and second industry standard protocols. Module  44  may also contain license code that will determine the functionality of device  22  with respect to the multiple protocols. For example, data residing within module  48  may indicate that device  22  is only authorized to operate within a single process industry standard mode, such as HART. Ultimately, a different setting of that data within module  48  may indicate that device  22  is authorized to operate in accordance with two or more industry standard protocols. Module  44  is preferably inserted to a connector  50  on the main board and may in fact require slight disassembly of device  22 , such as removing the battery pack to access port  50 .  
     [0032] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.