Serial port that supports multiple protocols
Contents
1. YOAN U 27 A VE Old 03u09 UOROW 26 9019p Of paynquysip YHOM U Ko 19 Jepun yun 001 US 7 725 627 B2 Sheet 4 of 7 May 25 2010 U S Patent 08 YHOM U R Ge 14 66 Ol 99920 0 U S Patent May 25 2010 Sheet 5 of 7 US 7 725 627 B2 FIG 3B 92 distributed I O device o o 5 Q ww U FIG device controller 82 U S Patent May 25 2010 read from serial port 402 data are framed by time 403 parse command according to time based protocol 404 Sheet 6 of 7 US 7 725 627 B2 data are framed by delimiters 405 determine delimiter based protocol 406 parse command according to delimiter based protocol 408 FIG 4 U S Patent May 25 2010 Sheet 7 of 7 US 7 725 627 B2 discard 216 read from serial port 402 no passed frame integrity check 515 determine time from last receive 504 determine delimiter based protocol and check frame integrity minimum framing timeout yes complete frame found 513 check time integrity 506 passed time integrity check 507 scan for delimiters 512 forvvard to delimiter framing checker 510 parse command according to delimiter based parse command according to time based pr2. parse command according to delimiter based protocol US 7 725 627 B2 Page 2 U S PATENT DOCUMENTS 2003 0174070 Al 9 2003 Garrod et al 340 870 07 2004 0138786 Al 7 2004 Blackett et al 700 295 2004 0177153 1 9 2004 Pelley 709 236 2005 0089054 Al 4 2005 Ciancaglini et al 370 412 2005 0094640 Al 5 2005 Howe 370 395 1 OTHER PUBLICATIONS NI Serial Hardware Specifications Guide Aug 2005 28 pages National Instruments Corporation NI ENET 232 4 4 Port Ethernet Interface for RS232 Datahseet Aug 2005 5 pages Retrieved from the Internet http www ni com pdf products us 4gpib716 677 680 pdf Lynn Linse The Agnostic View of Serial Bridging Protocols The Industrial Ethernet Technical Article Dec 2005 Issue 26 36 GGH Marketing Communications Limited cited by examiner US 7 725 627 B2 Sheet 1 of 7 May 25 2010 U S Patent 76 SO NPOW O VL Ola YOL WUNIPSW UOISSILISUEJJ EL S C8 0 US 7 725 627 B2 Sheet 2 of 7 2010 May 25 U S Patent Ves v6 ULOJS S J9 O1 U09 s lnpoul YOL wnIp w uoISsSIUsuUeJ 61 O l US 7 725 627 B2 Sheet 3 of 7 May 25 2010 U S Patent 69 0
3. and similar measurement test or auto mation instruments A measurement device may be further operable to perform control functions e g in response to analysis of the acquired or stored data For example the measurement device may send a control signal to an external system such as a motion control system or to a sensor in response to particular data A measurement device may also be operable to perform auto mation functions i e may receive and analyze data and issue automation control signals in response US 7 725 627 B2 7 FIGS 1A and 1B Distributed I O Systems FIGS 1A and 1B illustrate distributed I O systems suitable for implementing various embodiments of the present inven tion As may be seen FIG 1A illustrates a distributed I O sys tem that includes a controller 82 which may be referred to as a dedicated controller coupled to a distributed I O device 92 via a serial transmission medium 104 In this embodiment the distributed I O device 92 includes a plurality of I O mod ules 94 e g for data acquisition control automation signal generation and so forth as desired which may in turn be coupled to external devices e g units under test UUT motion control or automation devices etc In other embodi ments the I O functionality of one or more of the modules may be provided by one or more external devices coupled to the distributed I O device Note that as is well known in the art the controll
4. tocol wherein the time based protocol is automatically selected from a plurality of time based protocols with out user input specifying the time based protocol d if the data are determined to not be framed by time means for automatically determining that the data are framed by delimiters without user involvement means for automatically determining an appropriate delimiter based protocol for the data from a plurality of delimiter based protocols wherein the delimiter based protocol is automatically selected from the plu rality of delimiter based protocols without user input specifying the delimiter based protocol and means for handling the data according to the appropriate delimiter based protocol and means for repeating a d in an iterative manner to read a stream of data from the serial port
5. 5 illustrates a more detailed embodiment of the method for performing distributed T O described above vvith reference to FIG 4 The method shovvn in FIG 5 may be used in conjunction with any of the computer systems or devices shown in the above Figures among other devices In various embodiments some of the method elements shown may be performed concurrently performed in a different order than shown or omitted Additional method elements may also be performed as desired As shown this method may operate as follows Descriptions of method elements that are substan tially the same as those of FIG 4 are abbreviated First as shown in FIG 5 in 402 data may be read from a serial port as described above with reference to FIG 4 In 504 the time elapsed from last receipt of data may be determined and in 505 compared to a threshold value e g a minimum time based framing duration or timeout to deter mine if the data may be framed by time For example the data reception of 402 may occur at a current time of reception and a duration between reception of immediately previous received data and the current time of reception may be deter mined This duration may then be checked against a known minimum timing frame duration of a time based protocol 505 As mentioned above if the determined duration is greater than the threshold value then it is possible that the data may be formatted according to the time based protocol In one embodi
6. I O device the device coupled to a con troller may read data from a serial port may determine if the 51 Int Cl data are framed by time and if so may handle the data G06F 13 12 2006 01 according to a time based protocol If the data are not framed 52 U S CI 710 71 by time the device may determine if the data are framed by 58 Field a f Classification Search 2500 None delimiters and if so may determine an appropriate delimiter Sesnoplieaton file tor comble ie search histor based protocol for the data from a plurality of delimiter based PP P ry protocols and handle the data according to the appropriate 56 References Cited delimiter based protocol This process may be repeated in an U S PATENT DOCUMENTS 4 979 169 A 12 1990 Almond et al 5 841 992 A 11 1998 Martin 6 505 267 B2 1 2003 Luke etal 6 535 522 B1 3 2003 Arato et al 6 847 349 B2 1 2005 Azinger iterative manner to read a stream of data from the serial port The device may include or be coupled to one or more I O modules e g for DAQ motion control etc which them selves may be coupled to a unit under test or other external device or phenomenon via additional devices 20 Claims 7 Drawing Sheets read from serial port 402 data are framed by time 403 parse command according to time based protocol 404 data are framed by delimiters 405 determine delimiter based protocol IN 5 jep
7. be handled by the underlying time based software For example a message may be extracted from the data and the message parsed and interpreted Of course depend ing upon the particular message sent and extracted one or more operations may be performed in response e g signal generation acquisition storage etc with or by one or more of the I O modules and or devices coupled to the distributed I O device Ifin 507 the data did not pass the time integrity check then in 510 the data may be forwarded to a delimiter framing checker which may be operable to determine if the data are framed by delimiters For example as indicated in 512 the data may be scanned for delimiters associated with any of a plurality of delimiter based protocols Typically this scan ning will search for specified delimiter pairs defining a com plete frame data frame with respect to one of a plurality of delimiter based protocols In 513 a determination may be made as to whether a complete frame was found in 512 i e ifa specified delimiter pair defining a complete frame has been found in the data and if not the method may return to 402 to read the next data on the serial port and may proceed as described above Ifin 513 it is determined that delimiters are included in the data then an appropriate delimiter based protocol for the data may be determined based on the determined delimiters and an integrity check of the data may be performed in accor
8. windows may optionally be tiled together A GUI may be associated with a graphical program In this instance various mechanisms may be used to connect GUI Elements in the GUI with nodes in the graphical program For example when Input Controls and Output Indicators are cre ated in the GUI corresponding nodes e g terminals may be automatically created in the graphical program or block dia gram Alternatively the user can place terminal nodes in the block diagram which may cause the display of corresponding GUI Elements front panel objects in the GUI either at edit time or later at run time As another example the GUI may comprise GUI Elements embedded in the block diagram por tion of the graphical program Graphical User Interface Element an element of a graphical user interface such as for providing input or dis playing output Exemplary graphical user interface elements comprise input controls and output indicators Input Control a graphical user interface element for pro viding user input to a program Exemplary input controls comprise dials knobs sliders input text boxes etc Output Indicator a graphical user interface element for displaying output from a program Exemplary output indica tors include charts graphs gauges output text boxes numeric displays etc An output indicator is sometimes referred to as an output control Computer System any of various types of computing or processing systems
9. US007725627B2 az United States Patent 10 Patent No US 7 725 627 B2 Crain II et al 45 Date of Patent May 25 2010 54 SERIAL PORT THAT SUPPORTS MULTIPLE 6 865 235 B2 3 2005 Khoini Poorfard PROTOCOLS 7 035 247 B2 4 2006 Ofek et al 370 350 7 065 101 B2 6 2006 Ziegler et al 75 Inventors Charles E Crain II Austin TX US N gt Merag Jr et al 0022 tas 430 UNEN siiri ese Tony Widjaja Austin TX US 7 508 190 B2 3 2009 Kagan etal 324 142 73 Assignee National Instruments Corporation 2002 0018475 AL 2 2002 Ofek et al 370 400 Austin TX US Continued Notice Subject to any disclaimer the term of this OTHER PUBLICATIONS patent is extended or adjusted under 35 ENET 232 Series and ENET 485 Series User Manual for Windows U S C 154 b by 484 days 2000 NT 4 0 and Linux x86 Solaris 2 x Nov 2001 Edition 105 pages National Instruments Corporation 21 Appl No 11 560 071 Continued 22 Filed Nov 15 2006 Primary Examiner Tariq Hafiz Assistant Examiner Aurangzeb Hassan 65 Prior Publication Data 74 Attorney Agent or Firm Meyertons Hood Kivlin US 2007 0168590 A1 Jul 19 2007 Kowert amp Goetzel P C Jeffrey C Hood Joel L Stevens Related U S Application Data ABSTRACT wo System and method for performing distributed input output 60 P 1 application No 60 752 791 filed on Dec 60 2700 2000 I O A distributed
10. a stream of data from the serial port of the distributed I O device Note that in some embodiments the method may only support a single time based protocol or multiple time based protocols if and only if their inter message timeouts or dura tions are identical Note also that the methods described herein may support an arbitrary number of delimiter based protocols since the delimiter based handler may be capable of searching for multiple sets of begin end sequences simul taneously In some embodiments an assumption may be made that any protocols supported have some type of integrity check that indicates whether a message is valid or not such as a CRC check or checksum or any other integrity check desired As indicated above in preferred embodiments the meth ods described herein may be performed by one or more pro grams executing on the distributed I O device 92 The one or more programs may include one or more of a text based program such as C C JAVA etc or a graphical program where the graphical program includes a plurality of intercon nected nodes that visually indicate functionality of the graphical program Exemplary graphical programs include those developed under the LabVIEW graphical programming development system provided by National Instruments Corporation In some embodiments the graphical program may include or be a graphical data flow program As mentioned above the one or more programs imple menting em
11. a graphical pro gram and the program may execute on the controller 82 e g on a computer system 82A or other device The controller or computer system may be a platform that supports real time execution e g a device including a processor that executes a real time operating system RTOS or a device including a programmable hardware element In one embodiment of the invention one or more graphical programs may be created which are used in performing Hard ware in the Loop HIL simulation Hardware in the Loop HIL refers to the execution of the plant model 96 in real time to test operation ofa real controller 82 For example once the controller 82 has been designed it may be expensive and complicated to actually test the controller 82 thoroughly in a real plant e g areal car Thus the plant model implemented by a graphical program may be executed in real time to make the real controller 82 believe or operate as if it is connected to areal plant e g a real engine In the embodiments of FIGS 2A 2B and 3B above one or more of the various devices may couple to each other over a network such as the Internet In one embodiment the user may select a target device from a plurality of possible target devices for programming or configuration using a graphical program Thus the user may create a e g graphical pro gram on a computer and use execute the program on that computer or deploy the program to a target device fo
12. bodiments of the present invention preferably execute on the distributed I O device 92 For example at least a portion of the one or more programs may be executed on a processor included in the distributed I O device 92 In some embodiments at least a portion of the one or more programs may be executed on a programmable hardware element e g an FPGA included in the distributed I O device In further embodiments the distributed I O device 92 may include both a processor memory and a programmable hardware element where each executes a respective portion of the one or more programs implementing embodiments of the present inven tion Benefits Devices implementing embodiments of the techniques dis closed herein are the first devices to allow users to employ a variety of stream based protocols on a serial port with no configuration required In other words the device automati cally detects which protocol is being used e g on a message by message basis and responds appropriately More specifi cally the device detects the different framing conventions used by the different protocols Possible benefits resulting from use of these techniques include but are not limited to Improved manufacturing efficiency the fact that a single device i e a single product and part number may support multiple serial protocols without special configuration pre cludes having to offer a variety of products that differ only in the protocol framing co
13. d data e g allowing for the plug and play interface described above Thus in some embodiments the controller may dynamically determine and use various protocols without specific user configuration Finally as indicated the method elements 402 408 may be repeated in an iterative manner to read a stream of data from the serial port Note that in preferred embodiments the data may be read by a distributed I O device that includes the serial port e g the distributed I O device 92 coupled to a controller e g controller 82 or 82A via a serial transmission medium In various embodiments the serial transmission medium may be a synchronous or asynchronous serial transmission medium As described above the distributed I O device 92 may also be coupled to one or more devices e g I O modules 94 that may themselves be coupled to additional devices as discussed above with reference to FIGS 2A and 2B As also described US 7 725 627 B2 11 above in some embodiments one or more of the I O modules may be comprised in the distributed I O device i e may be inserted into slots in the distributed I O device or alterna tively may comprise external devices coupled to the distrib uted I O device via any of various transmission media In one embodiment one or more of the I O modules may be operable to perform measurement or control operations e g signal generation data acquisition motion control etc The data read from the se
14. dance with the determined delimiter based protocol i e a frame integrity check as indicated in 514 In 515 a determination may be made as to whether the data passed the frame integrity check and if the data passed the frame integrity check then in 508 the data may be handled according to the determined delimiter based protocol For example similar to above a message may be extracted from the data and the message parsed and interpreted in accor dance with the determined protocol As also described above depending upon the particular message sent and extracted one or more operations may be performed in response e g signal generation acquisition storage etc with or by one or more of the I O modules and or devices coupled to the dis tributed I O device In other words if the frame integrity check fails the data may be passed to the delimiter based handler which may assemble the discrete messages passed down from the time based handler then scan them for special sequences indicat ing the beginning and end of a frame If the sequences are found the message is checked for frame integrity and if the check succeeds passed to the underlying delimiter based software US 7 725 627 B2 13 Finally as FIG 5 indicates if the data did not pass the frame integrity check of 515 the data may be discarded and the method may return to 402 and may proceed as described above repeating 402 516 in an iterative manner to read
15. data acquisition and control application ina test and measurement application a machine vision application a process control application a man machine interface application a simula tion application or a hardware in the loop validation appli cation among others FIG 2B illustrates an exemplary industrial automation system 160 that may implement embodiments of the inven tion The industrial automation system 160 is similar to the instrumentation or test and measurement system 100 shown in FIG 2A Elements which are similar or identical to ele ments in FIG 2A have the same reference numerals for con venience The system 160 may comprise a controller 82 that connects to one or more devices via the distributed I O device 92 As noted above the controller 82 may comprise a CPU and memory and may operate via the distributed I O device 92 with the one or more devices coupled to process or device 150 to perform an automation function such as MMI Man Machine Interface SCADA Supervisory Control and Data Acquisition portable or distributed data acquisition process control advanced analysis and or other control among oth ers The one or more devices may include a motion control device 136 and or a sensor e g transducer 170 among other types of devices The controller 82 may couple to and operate with one or more of these devices via the distributed VO device 92 which may include various instruments e g DAQ devices inter
16. dium and executed by a processor Exemplary software programs include programs written in text based program ming languages such as C C Pascal Fortran Cobol Java assembly language etc graphical programs programs writ ten in graphical programming languages assembly language programs programs that have been compiled to machine language scripts and other types of executable software A software program may comprise two or more software pro grams that interoperate in some manner Hardware Configuration Program a program e g a netlist or bit file that can be used to program or configure a programmable hardware element Graphical User Interface this term 1s intended to have the full breadth of its ordinary meaning The term Graphical User Interface is often abbreviated to GUT A GUI may comprise only one or more input GUI elements only one or more output GUI elements or both input and output GUI elements The following provides examples of various aspects of GUIs The following examples and discussion are not intended to limit the ordinary meaning of GUI but rather provide examples of what the term graphical user interface encompasses 5 40 45 50 55 65 6 A GUI may comprise a single window having one or more GUI Elements or may comprise a plurality of individual GUI Elements or individual windows each having one or more GUI Elements wherein the individual GUI Elements or
17. er includes some type of processor and memory but may have limited or no stand alone user interface capabilities i e generally does not include a display device and so may rely on a host computer system for user input e g configuration programming etc FIG 1B illustrates a distributed I O system that uses a desktop computer or workstation as a controller specifically controller computer system 82A where the controller com puter system is coupled to the distributed I O device 92 via the serial transmission medium 104 The controller computer system 82A or controller 82 of FIG 1A may operate to execute a program e g a text based or graphical program e g application which may commu nicate with the distributed I O device 92 to perform specified functionality e g a measurement control or automation function among others Note that as used herein the term controller may be used generally to refer to either type of controller i e PC work station based FIG 1B or compact FIG 1A The controller may include a memory medium s on which one or more computer programs or software components according to one embodiment of the present invention may be stored For example the memory medium may store one or more text based programs e g C C JAVA etc and or graphical programs e g LabVIEW graphical programs IEC 61131 ladder logic or function block diagrams etc that are executable to perform the meth
18. erence static discharge etc much more so than PCs or consumer level electronics Some typical applications for distributed I O devices are factory automation the devices are deployed around a factory and used to monitor and control devices associ ated with a manufacturing process For example they may drive a conveyor belt or monitor the temperature in a boiler and control the heater attached to it machine control related to factory automation but on a smaller scale the device is deployed on a machine and used to control operations of the machine e g large washers that wash silicon wafers prior to etching into semiconductor chips trucks that service oil wells and so forth product testing the devices are often used to control and monitor large scale product testing rigs data logging the computer or controller connected to the device typically continuously requests data and logs the data to disk or a similar medium for later retrieval and analysis A controller may be thought of as a computer with the same rugged form as a distributed I O device i e a rugged distrib uted device that also includes programmability and intelli gence For example National Instruments controllers some time referred to as programmable automation controllers PACs allow users to write LabVIEW e g graphical pro grams then download them to the controllers which then run them autonomously Distributed I O devices provide c
19. es a consistency check such as a check sum or cyclic redundancy check CRC that ensures integrity of the message Serial media such as RS 232 do not have standard framing conventions and therefore each individual distributed I O protocol is free to define its own In general framing conven tions fall into two categories 1 Time based the beginning and end of messages are defined by pauses between messages For example a speci fication for a time based framing convention might indicate that the end of a message occurs after a pause of greater than 100 milliseconds or as another example greater than 64 bit times where a bit time is the time required for the medium to transmit one bit of data An example of a protocol with time based framing is Modbus RTU 2 Delimiter based the beginning and end of messages is indicated by some special sequence of bits that is guaranteed never to occur in the middle or body ofa valid message Valid data reside between the beginning and end sequences and any other data are disregarded Examples of delimiter based protocols are Modbus ASCII and OptoMUX Currently distributed I O devices generally support only a single protocol with a single framing convention Thus cus tomers must order the specific device that supports the pro tocol they wish to employ Some more sophisticated devices allow the user to configure the device to accept a variety of protocols that the device supports However no c
20. face cards e g for motion control etc in the form of I O modules 94 The devices may in turn be coupled to a unit under test UUT or process 150 As also shown the distributed I O device may also be operable to receive signals directly from the UUT or process 150 via a direct channel 180 The system 100 may be used in a data acquisition and control application ina test and measurement application a machine vision application a process control application a man machine interface application a simula tion application and or a hardware in the loop validation application among others US 7 725 627 B2 9 FIG 3A is a high level block diagram of an exemplary system that may execute or utilize programs according to the present invention FIG 3A illustrates a general high level block diagram of a generic control and or simulation system that comprises a controller 82 a distributed I O device 92 and a plant 96 The controller 82 represents a control system algorithm the user may be trying to develop The distributed VO device 92 represents the distributed I O interface between the controller 82 and the plant 96 The plant 96 represents the system the user may be trying to control For example if the user is designing an electronic control unit ECU for a car the controller 82 is the ECU and the plant 96 is the car s engine and possibly other components such as transmission brakes and so on As shown a user may create a prog
21. floppy disks 104 or tape device a computer system memory or random access memory such as DRAM DDR RAM SRAM EDO RAM Rambus RAM etc or a non volatile memory such as a magnetic media e g a hard drive or optical storage The memory medium may comprise other types of memory as well or combinations thereof In addi tion the memory medium may be located in a first computer in which the programs are executed or may be located in a second different computer which connects to the first com US 7 725 627 B2 5 puter over a network such as the Internet In the latter instance the second computer may provide program instruc tions to the first computer for execution The term memory medium may include two or more memory mediums which may reside in different locations e g in different computers that are connected over a network Carrier Medium a memory medium as described above as well as signals such as electrical electromagnetic or digi tal signals conveyed via a communication medium such as a bus network and or a wireless link Programmable Hardware Element includes various types of programmable hardware reconfigurable hardware programmable logic or field programmable devices FPDs such as one or more FPGAs Field Programmable Gate Arrays or one or more PLDs Programmable Logic Devices such as one or more Simple PLDs SPLDs or one or more Complex PLDs CPLDs or other types of program mable hardware A
22. including a personal computer system PC mainframe computer system workstation network appliance Internet appliance personal digital assistant PDA television system grid computing system or other device or combinations of devices In general the term com puter system can be broadly defined to encompass any device or combination of devices having at least one pro cessor that executes instructions from a memory medium Measurement Device includes instruments data acqui sition devices smart sensors and any of various types of devices that are operable to acquire and or store data A mea surement device may also optionally be further operable to analyze or process the acquired or stored data Examples of a measurement device include an instrument such as a tradi tional stand alone box instrument a computer based instrument instrument on a card or external instrument a data acquisition card a device external to a computer that operates similarly to a data acquisition card a smart sensor one or more DAQ or measurement cards or modules in a chassis an image acquisition device such as an image acqui sition or machine vision card also called a video capture board or smart camera a motion control device a robot having machine vision and other similar types of devices Exemplary stand alone instruments include oscilloscopes multimeters signal analyzers arbitrary waveform genera tors spectroscopes
23. ion may be made as to whether the data are framed by time and if so then in 404 the data may be handled according to a time based protocol Note that the time based protocol may be selected from a plurality of avail able time based protocols e g including a Modbus RTU protocol among others In some embodiments the time based protocol may be determined automatically i e without user input specifying the time based protocol Thus the time based protocol may be determined based on the received data e g in order to allow for a plug and play framework for the distributed system Thus in some embodiments the control ler may dynamically determine and use various protocols without specific user configuration If the data are determined to not be framed by time then in 405 a determination may be made as to whether the data are framed by delimiters If the data are determined to be framed by delimiters then in 406 an appropriate delimiter based protocol for the data from a plurality of delimiter based protocols may be deter mined and in 408 the data may be handled according to the appropriate delimiter based protocol The plurality of delim iter based protocols may include Modbus ASCII and or OptoMUX among others Similar to above the determina tion of the delimiter based protocol may be performed auto matically without user input selecting the delimiter based protocol The protocol may be selected based on the receive
24. iter based protocols since the delimiter based handler may be capable of searching for multiple sets of begin end sequences simul taneously Furthermore an assumption may be made that any proto cols supported have some type of integrity check that indi cates whether a message is valid or not such as a CRC check 20 25 35 40 45 50 55 60 65 4 or checksum or any other integrity check desired Thus the method may include performing integrity checks and verify ing those checks Thus various embodiments of the above method may oper ate to dynamically read serial data streamed from a serial port in accordance with any of a variety of communication proto cols without requiring configuration e g user configuration of the system BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the present invention can be obtained when the following detailed description of the pre ferred embodiment is considered in conjunction with the following drawings in which FIGS 1A and 1B illustrate distributed I O systems suitable for implementing various embodiments of the present inven tion FIG 2A illustrates an instrumentation control system according to one embodiment of the invention FIG 2B illustrates an industrial automation system accord ing to one embodiment of the invention FIG 3A is a high level block diagram of an exemplary system which may execute or utilize programs according to some embodi
25. limiter based protocol for the data from a plu rality of delimiter based protocols may be determined and the data may be handled according to the appropriate delim iter based protocol Similar to above the determination of the delimiter based protocol may be performed automatically without user input selecting the delimiter based protocol The protocol may be selected based on the received data e g allowing for the plug and play interface described above Thus in some embodiments the controller may dynamically determine and use various protocols without specific user configuration Finally as indicated the method may be repeated in an iterative manner to read a stream of data from the serial port Note that the data may be read by a distributed I O device that includes the serial port coupled to a controller via a serial transmission medium In various embodiments the serial transmission medium may be a synchronous or asyn chronous serial transmission medium The distributed I O device may also be coupled to one or more devices that may themselves be coupled to additional devices One or more of the I O modules may be comprised in the distributed I O device i e may be inserted into slots in the distributed I O device or alternatively may comprise external devices coupled to the distributed I O device via any of various trans mission media In one embodiment one or more of the I O modules may be operable to perform measureme
26. ment for example a server process execut ing on the distributed I O device preferably a FieldPoint device may constantly gather data from the RS 232 port and measure the time between characters received If in 505 it is determined that the duration exceeds the specified value an integrity check of the data may be per 20 25 30 35 40 45 50 55 60 65 12 formed in accordance with the time based protocol i e a time integrity check as indicated in 506 Any type of integrity check consistent with the time based protocol may be used as desired including but not limited to cyclic redundancy check CRC checksum and so forth Note that in some embodiments a particular time based protocol may be deter mined from a plurality of possible time based protocols e g based on analysis of the received data and or the determined duration Said another way if the time exceeds the minimum inter message time for a time based framing convention the intact message may be passed to a handler for time based protocols which may subject the data to the time integrity test As FIG 5 also shows in 507 a determination may be made as to whether the data passed the time integrity check of 506 and if the data passed the time integrity check then in 508 the data may be handled according to the time based protocol In other words the message may be checked for integrity and if the check is successful the message may
27. ments FIG 3B illustrates an exemplary system which may per form control and or simulation functions FIG 4 is a flowchart diagram illustrating one embodiment of a method for performing distributed I O and FIG 5 is a flowchart diagram illustrating a more detailed embodiment of a method for performing distributed I O While the invention is susceptible to various modifications and alternative forms specific embodiments thereof are shown by way of example in the drawings and are herein described in detail It should be understood however that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed but on the contrary the intention is to cover all modifications equiva lents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Incorporation by Reference Provisional Application Ser No 60 752 791 entitled Serial Port that Supports Multiple Protocols whose inven tors were Charles E Crain II and Tony Widjaja is hereby incorporated by reference in its entirety as though fully and completely set forth herein Terms The following is a glossary of terms used in the present application Memory Medium Any of various types of memory devices or storage devices The term memory medium is intended to include an installation medium e g a CD ROM
28. nt or control operations e g signal generation data acquisition motion control etc The data read from the serial port may include commands sent from the controller e g specifying one or more opera tions to be performed with or by the devices coupled to the distributed I O device For example a first I O module may include a signal generator that may be operable to provide a stimulus signal to a unit under test UUT A second I O module may include a DAQ device that may be operable to receive resultant signals from the UUT in response to the provided stimulus signal The controller may thus send a command to the distributed I O device invoking the genera tion of the stimulus signal via the first I O module and may also send a command specifying that the second module acquire the resulting signals and send them to the controller or another device for storage and or analysis Thus the distributed I O device may communicate with e g may send and receive data to and from the controller e g in accor dance with the determined communication protocol Note that in some embodiments a command may be assembled from data received over multiple read cycles Note that in some embodiments the method may only support a single time based protocol or multiple time based protocols if and only if their inter message timeouts or dura tions are identical Note also that the methods described herein may support an arbitrary number of delim
29. nvention that they are pre configured to support No configuration the user does not have to specify which protocol they want to use The device is plug and play and recognizes any protocol that it supports out of the box Ease of ordering customers and salespeople do not need to decide which product is appropriate since the single prod uct supports many serial protocols 20 25 30 35 40 45 50 55 60 65 14 Engineering efficiency because support and mainte nance of multiple products is not reguired nor support main tenance and documentation of a configuration interface the device is less expensive in terms ofnon recurring engineering and expense and ongoing support Although the embodiments above have been described in considerable detail numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated It is intended that the follow ing claims be interpreted to embrace all such variations and modifications We claim 1 A method for performing distributed input output 1 0 the method comprising using a computer to perform a receiving data from a serial port coupled to a serial transmission medium b automatically determining if the data are framed by time wherein said automatically determining if the data are framed by time is performed without user involve ment c if the data are determined to be framed by
30. ods described herein Also in the controller computer system embodiments the memory medium may store a graphical programming development environment application used to create and or execute such graphical programs The memory medium may also store operating system software as well as other software for operation of the computer system Various embodiments fur ther include receiving or storing instructions and or data implemented in accordance with the foregoing description upon a carrier medium Further details of the operation of the distributed I O device are provided below Exemplary Systems Embodiments of the present invention may be involved with performing test and or measurement functions control ling and or modeling instrumentation or industrial automa tion hardware modeling and simulation functions e g mod eling or simulating a device or product being developed or tested etc Exemplary test applications where the graphical program may be used include hardware in the loop testing and rapid control prototyping among others However it is noted that the present invention can be used for a plethora of applications and is not limited to the above 20 25 30 35 40 45 50 55 60 65 8 applications In other words applications discussed in the present description are exemplary only and the present inven tion may be used in any of various types of systems Thus the system and method of the presen
31. ontrol lers an affordable way distributed I O devices cost less than controllers to extend the amount of I O that a controller can perform or manage and also distribute that I O to where it needs to be physically Of course a standard PC or worksta tion or laptop may also be used as a controller environmen tal conditions permitting 15 20 25 30 35 40 45 50 55 60 65 2 The data communicated between the controller and the distributed I O device are transmitted over a variety of media using a variety of protocols many of which are open stan dards A common medium for data transmission used by these devices is serial e g using RS 232 RS 422 or RS 485 interfaces These media transmit data in streams in which individual bits of data are sent in sequence This is in contrast to a medium such as Ethernet which sends data in packets which are large 1 e multi bit or multi byte sets of data with a defined beginning and ending Transmitting distributed I O data over a stream based medium has a central challenge distributed I O protocols are message based i e consisting of discrete large data sets and are therefore better suited for packet based media Therefore any distributed I O protocol that travels over a stream based medium must have some type of framing convention which is an aspect of the protocol that defines where a message begins and ends The distributed I O protocol often includ
32. otocol 404 protocol 408 FIG 5 yes US 7 725 627 B2 1 SERIAL PORT THAT SUPPORTS MULTIPLE PROTOCOLS PRIORITY This application claims benefit of priority of U S provi sional application Ser No 60 752 791 titled Serial Port that Supports Multiple Protocols filed Dec 21 2005 whose inventors were Charles E Crain II and Tony Widjaja FIELD OF THE INVENTION The present invention relates to the field of serial commu nications and more particularly to a system and method for serial communications supporting multiple protocols DESCRIPTION OF THE RELATED ART A distributed I O device performs measurements and gen erates signals based on data e g commands transmitted from a host device typically a computer or controller The distributed I O device is generally coupled to one or more modules that acquire data or generate signals based on the commands received from the controller and in the case of data acquisition DAQ may transmit the acquired data to the host controller or to another external device Many applications involve measurements or devices to control in environments for which it is physically inconve nient or impossible to deploy a system based on personal computers PCs or consumer level electronics In these situ ations distributed I O devices are often used because they are typically rated very highly for resistance to extreme tempera tures shock vibration electromagnetic interf
33. programmable hardware element may also be referred to as reconfigurable logic Medium includes one or more of a memory medium carrier medium and or programmable hardware element encompasses various types of mediums that can either store program instructions data structures or can be configured with a hardware configuration program For example a medium that is configured to perform a function or imple ment a software object may be 1 a memory medium or carrier medium that stores program instructions such that the program instructions are executable by a processor to perform the function or implement the software object 2 a medium carrying signals that are involved with performing the func tion or implementing the software object and or 3 a pro grammable hardware element configured with a hardware configuration program to perform the function or implement the software object Program the term program is intended to have the full breadth of its ordinary meaning The term program includes 1 a software program which may be stored in a memory and is executable by a processor or 2 a hardware configuration program useable for configuring a program mable hardware element Software Program the term software program is intended to have the full breadth of its ordinary meaning and includes any type of program instructions code script and or data or combinations thereof that may be stored in a memory me
34. r remote execution on the target device that is remotely located from the computer and coupled to the computer through a network 20 25 30 35 40 45 50 55 60 65 10 In some embodiments the target device may include the controller 82 various portions of the distributed I O device 92 and or any other systems described herein among others Graphical software programs which perform data acquisi tion analysis and or presentation e g for measurement instrumentation control industrial automation modeling and or simulation such as in the applications shown in FIGS 2A and 2B may be referred to as virtual instruments FIG 4 Method for Performing Distributed I O FIG 4 illustrates one embodiment of a method for per forming distributed I O via any of a plurality of protocols without configuration The method shown in FIG 4 may be used in conjunction with any of the computer systems or devices shown in the above Figures among other devices In various embodiments some of the method elements shown may be performed concurrently performed in a different order than shown or omitted Additional method elements may also be performed as desired As shown this method may operate as follows In 402 data may be received i e read from a serial port e g an RS 232 port although it should be noted that any other type of serial port may be used as desired e g RS 422 RS 485 etc In 403 a determinat
35. ram e g a graphical program that specifies or implements the functionality of one or all of the controller 92 the distributed VO device 92 and the plant 96 For example a control engi neer may use a modeling and simulation tool to create a model e g a graphical program of the plant 96 and or to imple ment the algorithm for the controller 92 and possibly for the distributed I O device 92 FIG 3B illustrates an exemplary system that may perform control and or simulation functions As shown the controller 82 may be implemented by a computer system 82A or other device e g including a processor and memory medium and or including a programmable hardware element that executes or implements embodiments of the present inven tion In a similar manner the plant 96 may be implemented by a computer system or other device 144 e g including a processor and memory medium and or including a program mable hardware element that executes or implements a graphical program or may be implemented in or as a real physical system e g a car engine In one embodiment of the invention one or more graphical programs may be created which are used in performing rapid control prototyping Rapid Control Prototyping RCP gen erally refers to the process by which a user develops a control algorithm and quickly executes that algorithm on a target controller connected to a real system The user may develop the control algorithm using a program e g
36. rial port may include commands sent from the controller e g specifying one or more opera tions to be performed with or by the devices coupled to the distributed I O device For example a first I O module may include a signal generator that may be operable to provide a stimulus signal to a unit under test UUT A second I O module may include a DAQ device that may be operable to receive resultant signals from the UUT in response to the provided stimulus signal The controller may thus send a command to the distributed I O device invoking the genera tion of the stimulus signal via the first I O module and may also send a command specifying that the second module acquire the resulting signals and send them to the controller or another device for storage and or analysis Thus the distributed I O device may communicate with e g may send and receive data to and from the controller e g in accor dance with the determined communication protocol Note that in some embodiments a command may be assembled from data received over multiple read cycles Thus various embodiments of the above method may oper ate to dynamically read serial data streamed from a serial port in accordance with any of a variety of communication proto cols without requiring configuration of the system A more detailed embodiment of the method of FIG 4 is described below with reference to FIG 5 FIG 5 More Detailed Method for Performing Distributed VO FIG
37. serial port 19 A computer accessible memory medium that stores program instructions executable by a processor to a receive data from a serial port coupled to a serial trans mission medium b automatically determine if the data are framed by time without user involvement c if the data are determined to be framed by time handle the data according to a time based protocol wherein the time based protocol is automatically selected from a plurality of time based protocols without user input specifying the time based protocol d if the data are determined to not be framed by time automatically determine that the data are framed by delimiters without user involvement automatically determine an appropriate delimiter based protocol for the data from a plurality of delimiter based protocols wherein the delimiter based protocol is automatically selected from the plurality of delim iter based protocols without user input specifying the delimiter based protocol and handle the data according to the appropriate delimiter based protocol and e repeat a d in an iterative manner to read a stream of data from the serial port 20 A system comprising means for a receiving data from a serial port coupled to a serial transmission medium means for b automatically determining if the data are framed by time without user involvement means for c if the data are determined to be framed by time handling the data according to a time based pro
38. t invention is operable to be used in any of various types of applications including the control of other types of devices such as multimedia devices video devices audio devices telephony devices Internet devices etc as well as general purpose software applica tions such as network control network monitoring financial applications games etc FIG 2A illustrates an exemplary instrumentation control system 100 which may implement embodiments of the inven tion The system 100 comprises a controller 82 which con nects to one or more devices via the distributed I O device 92 As noted above the controller 82 may comprise a CPU and memory The controller 82 may operate with the one or more devices through the distributed I O device 92 to analyze measure and or control a unit under test UUT or process 150 The one or more devices may include a motion control device 136 and or a sensor e g transducer 170 among other types of devices The controller 82 may couple to and operate with one or more of these devices via the distributed VO device 92 which may include various instruments e g DAQ devices interface cards e g for motion control etc in the form of I O modules 94 The devices may in turn be coupled to a unit under test UUT or process 150 As also shown the distributed I O device may also be operable to receive signals directly from the UUT or process 150 via a direct channel 180 The system 100 may be used in a
39. ted I O device 9 The method of claim 8 wherein the one or more pro grams comprise one or more of a text based program or a graphical program wherein the graphical program com prises a plurality of interconnected nodes that visually indicate functionality of the graphical program 10 The method of claim 9 wherein the graphical program comprises a graphical data flow program 11 The method of claim 8 wherein at least a portion of the one or more programs is executed on a processor comprised in the distributed I O device 12 The method of claim 8 wherein at least a portion of the one or more programs is executed on a programmable hard ware element comprised in the distributed I O device 13 The method of claim 8 wherein the data are received from a controller coupled to the distributed I O device via the serial transmission medium 14 The method of claim 13 wherein the controller com prises one or more of a desktop computer system or a dedicated controller 15 The method of claim 13 further comprising the distributed I O device sending further data to the con troller via the serial transmission medium 16 The method of claim 8 wherein the distributed I O device is coupled to one or more I O modules wherein the one or more I O modules comprise one or more of a data acquisition DAQ device a motion control device or a signal generation device 17 The method of claim 1 wherein the time based pro
40. time handling the data according to a time based protocol wherein the time based protocol is automatically selected from a plurality of time based protocols without user input specifying the time based protocol d if the data are determined to not be framed by time automatically determining that the data are framed by delimiters wherein said automatically determining that the data are framed by delimiters is performed without user involvement automatically determining an appropriate delimiter based protocol for the data from a plurality of delim iter based protocols wherein the delimiter based pro tocol is automatically selected from the plurality of delimiter based protocols without user input specify ing the delimiter based protocol and handling the data according to the appropriate delimiter based protocol and e repeating a d in an iterative manner to read a stream of data from the serial port 2 The method of claim 1 wherein said receiving data comprises receiving the data at a current time of reception and wherein said automatically determining if the data are framed by time comprises determining a duration between reception of immediately previous received data and the current time of reception and if the determined duration exceeds a specified value per forming an integrity check of the data in accordance with the time based protocol 3 The method of claim 1 wherein said handling the data according to the
41. time based protocol comprises extracting a message from the data and parsing the message 4 The method of claim 3 wherein said handling the data according to the time based protocol further comprises performing an integrity check of the data in accordance with the time based protocol 5 The method of claim 1 wherein said automatically determining that the data are framed by delimiters comprises scanning the data for delimiters associated with any of the plurality of delimiter based protocols and determining that delimiters are included in the data and US 7 725 627 B2 15 wherein said automatically determining an appropriate delimiter based protocol for the data from a plurality of delimiter based protocols comprises determining the appropriate delimiter based protocol for the data based on the determined delimiters the method further comprising performing an integrity check of the data in accordance with the determined appropriate delimiter based pro tocol 6 The method of claim 5 wherein said handling the data according to the appropriate delimiter based protocol com prises extracting a message from the delimited data and parsing the message 7 The method of claim 1 wherein the serial transmission medium comprises a synchronous serial transmission medium or an asynchronous serial transmission medium 8 The method of claim 1 wherein a e are performed by one or more programs executing on a distribu
42. to col or the delimiter based protocol is determined automati cally without user input selecting the time based protocol or the delimiter based protocol 18 A distributed data acquisition system comprising distributed I O device comprising a serial port and acontroller coupled to the serial port of the distributed I O device via a serial transmission medium wherein the distributed I O device is operable to a read data from the serial port b automatically determine if the data are framed by time without user involvement c if the data are determined to be framed by time handle the data according to a time based protocol wherein 20 25 30 35 40 45 50 55 60 16 the time based protocol is automatically selected from a plurality of time based protocols without user input specifying the time based protocol d if the data are determined to not be framed by time automatically determine that if the data are framed by delimiters time without user involvement automatically determine an appropriate delimiter based protocol for the data from a plurality of delimiter based protocols wherein the delimiter based protocol is automatically selected from the plurality of delimiter based protocols without user input specifying the delimiter based protocol and handle the data according to the appropriate delim iter based protocol and e repeat a d in an iterative manner to read a stream of data from the
43. urrently available devices allow the user to employ any of a variety of protocols with different framing conventions without first having to configuring the device to accept the specific proto col desired Thus improved systems and methods for serial communi cations are desired SUMMARY OF THE INVENTION One embodiment of a method for performing distributed VO via any of a plurality of protocols without configuration The method may operate as follows Data may be received 1 e read from a serial port e g an RS 232 port although it should be noted that any other type of serial port may be used as desired e g RS 422 RS 485 etc A determination may be made as to whether the data are framed by time and if so then the data may be handled according to a time based protocol In some embodiments the time based protocol may be determined automatically 1 e without user input specifying the time based protocol Thus the time based protocol may be determined based on the received data e g in order to allow for a plug and play US 7 725 627 B2 3 framework for the distributed system Thus in some embodi ments the controller may dynamically determine and use various protocols without specific user configuration If the data are determined to not be framed by time a determination may be made as to whether the data are framed by delimiters If the data are determined to be framed by delimiters an appropriate de
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