EP1031209A1 - Appareil de mesure de la charge de bus utilisant un detecteur d'enveloppe numerique - Google Patents

Appareil de mesure de la charge de bus utilisant un detecteur d'enveloppe numerique

Info

Publication number
EP1031209A1
EP1031209A1 EP98952859A EP98952859A EP1031209A1 EP 1031209 A1 EP1031209 A1 EP 1031209A1 EP 98952859 A EP98952859 A EP 98952859A EP 98952859 A EP98952859 A EP 98952859A EP 1031209 A1 EP1031209 A1 EP 1031209A1
Authority
EP
European Patent Office
Prior art keywords
frame
meter
bus
meter according
output
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98952859A
Other languages
German (de)
English (en)
Inventor
Richard Thomas Mclaughlin
Kiah Hion Warwick Manufacturing Group Int. TANG
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Warwick
Original Assignee
University of Warwick
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University of Warwick filed Critical University of Warwick
Publication of EP1031209A1 publication Critical patent/EP1031209A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L12/407—Bus networks with decentralised control
    • H04L12/413—Bus networks with decentralised control with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD]
    • H04L12/4135—Bus networks with decentralised control with random access, e.g. carrier-sense multiple-access with collision detection [CSMA-CD] using bit-wise arbitration
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R16/00—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for
    • B60R16/02—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements
    • B60R16/03—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for
    • B60R16/0315—Electric or fluid circuits specially adapted for vehicles and not otherwise provided for; Arrangement of elements of electric or fluid circuits specially adapted for vehicles and not otherwise provided for electric constitutive elements for supply of electrical power to vehicle subsystems or for using multiplexing techniques
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/28—Data switching networks characterised by path configuration, e.g. LAN [Local Area Networks] or WAN [Wide Area Networks]
    • H04L12/40—Bus networks
    • H04L2012/40208—Bus networks characterized by the use of a particular bus standard
    • H04L2012/40215—Controller Area Network CAN
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
    • H04L43/0852—Delays
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/08—Monitoring or testing based on specific metrics, e.g. QoS, energy consumption or environmental parameters
    • H04L43/0876—Network utilisation, e.g. volume of load or congestion level
    • H04L43/0882—Utilisation of link capacity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L43/00—Arrangements for monitoring or testing data switching networks
    • H04L43/16—Threshold monitoring

Definitions

  • This invention relates to bus loading meters for monitoring the loading of a data bus.
  • GB 2280574 A discloses local area network (LAN) monitoring circuitry for preventing unauthorised use of services.
  • Such circuitry incorporates a data rate detector circuit for each user port which counts data pulses for each service in use during a preset clock period. If the count exceeds a predetermined value, the user is disconnected from that particular service.
  • Such monitoring circuitry is not capable of providing a direct indication of the bus loading of a network such as a CAN network.
  • SUBSTITUTE SHEET (RU.LE 25) It is an object of the invention to provide a bus loading meter which is capable of providing a direct indication of the bus loading of a CAN network at reasonable cost.
  • Figure 1 is a graph of the percentage bus loading of a CAN against latency
  • FIG. 1 is an explanatory diagram
  • Figure 3 is a block diagram of the meter
  • Figure 4 is a timing diagram of the meter
  • Figure 5 is a circuit diagram of the meter
  • Figure 6 is a table providing a comparison of the actual bus load and the readout from the meter.
  • Figure 2 shows the form of a typical CAN message in which the start-of- frame (SOF) 2 is indicated by a dominant bit, and the end-of-frame (EOF) 4 is indicated by seven recessive bits, only the last two of which are shown.
  • SOF start-of- frame
  • EEF end-of-frame
  • the meter detects the SOF 2 and the EOF 4, and calculates the average (mean) value of the message frame 6 in order to determine the percentage loading of the bus. Furthermore, using the mean value theorem, the average value of a square wave may be calculated from
  • This mean value represents the percentage bus loading.
  • FIG. 3 is a block diagram of the bus loading meter which comprises a CAN transceiver 10 which converts the incoming CAN signal to a standard digital (TTL) signal, and a counter 20 for capturing the SOF and EOF of the signal by calculating the number of recessive bits present immediately before a dominant bit (to determine the SOF) and after a dominant bit (to determine the acknowledgement slot), which is followed by seven successive recessive bits indicating the EOF.
  • TTL standard digital
  • the meter further comprises a message frame converter 30 which is triggered by receipt of a start pulse from the counter 20 to start counting, such counting being subsequently terminated on receipt of an end pulse from the counter 20 which resets the converter 30, forming a message envelope at the output of the converter 30 which is supplied to a voltmeter 40 providing a visual indication of the percentage bus loading.
  • the converter 30 is controlled by a frequency switch 32 supplied with a 16 MHz (or 8 MHz) frequency signal by a crystal oscillator 34.
  • the timing diagram of Figure 4 shows the relative timing of the signals in such a meter, the CAN signal being simplified with only a few bits being shown to indicate the SOF and EOF.
  • the bus idle time is indicated by the "off period of the digital envelope.
  • the circuit diagram of Figure 6 shows the various components of the meter in more detail, including the CAN transceiver 10, the 12-stage binary counter 20, the frequency switch 32, the EOF detector 35, the frame converter 30 and a power supply 36.
  • the power supply 36 comprises a power FET Ql, a zener diode Dl, a 5v supply circuit 37, and associated capacitors Cl and C2 and resistors R5 and R6.
  • a switch SI is provided for selection of a data rate of 125 Kbaud, 250 Kbaud or 500 Kbaud depending on the particular application. For each of these data rates the output of the counter 20 is supplied to the EOF detector 35 by a jumper Jl.
  • a data rate of 1 Mbaud may be selected if the output of the counter 20 is supplied to the EOF detector 35 by a jumper J2.
  • the circuit as shown uses the 8 MHz output from the frequency switch 32, although it is also possible to make use of the 16 MHz output from the switch 32 in some applications.
  • the RXD pin of the transceiver 10 is set to logic 0 and the resulting output signal is supplied to the J-input of the converter 30 by way of a Hex converter
  • the CLK input of counter 20 receives 8 MHz pulses from the frequency switch 32
  • SUBSTTTUTE SHEET (RULE 26) supplied with a frequency signal by the oscillator 34.
  • a clear signal is supplied to the CLR input of the counter 20 so as to reset the counter.
  • the counter 20 then counts the number of pulses equivalent to the width of the 8 recessive bits until the EOF detector 35 detects a logic 1 at the pin Jl or J2 of the counter 20 causing a 0 to be applied to the CLR input of the converter 30 which in turn causes the Q output of the converter 30 to be set to logic 0.
  • the Q output of the converter 30 will be set to logic 1 only when the J input is high, and the only condition that will cause the Q output to be set to logic 0 is when the CLR input of the converter 30 is set to 0.
  • the EOF of a CAN signal will cause the Q output of the converter 30 to go low. Subsequently any dominant bit on the bus will trigger the Q output of the converter 30 to go high again.
  • the table of Figure 5 shows measured percentage bus loading values obtained by the bus loading meter as compared with the corresponding calculated values obtained from the time between two messages (cycle time) and the message frame time.
  • a single device was connected to the bus, in addition to the meter, and the device was used to permanently transmit a duplicate MAC ID check message.
  • the message was simultaneously detected by an oscilloscope to enable the actual values to be calculated for the continually repeated message.
  • the table indicates the high accuracy of the meter in measuring the percentage loading.
  • the meter can be used in any CAN system or its application networks, such as DeviceNet, Smart Distributed System (SDS), CANKingdom, CANOpen or other proprietary systems.
  • CAN Smart Distributed System
  • CANKingdom CANOpen
  • CANOpen CANOpen
  • a network fails it transmits no signal (0 percent) or repeatedly transmits a frame (80+%) or operates in some other condition that does not match the protocol specification.
  • the resulting bus loading indicates that the bus has failed. It is envisaged, therefore, that such a meter may be used as an inexpensive check tool to check the bus loading of a vehicle, for example when the vehicle has failed on the road. If the bus loading is found to be different from the specified value, it can be concluded that at least one of the nodes has failed to function.
  • the meter may also be used by a system developer to verify that there is no latency problem in the system design.
  • the bus loading meter as described is particularly advantageous as it can be produced at low cost and so as to be made particularly compact. Furthermore an external voltage supply is optional as the supply voltage can be taken directly from the CAN system depending on the application network.
  • the meter may be adapted to support a wide range of frequencies (up to 1 Mbps), and no programming of the device is required. Furthermore the meter is a virtual device which does not provide a load to the bus, that is it does not have any identifier and does not respond to any CAN signal.
  • a variant of such a meter can be designed for use with networks other than CAN, such as, for example, Ethernet (Manchester Coding), J1850(PWM), VAN (enhanced Manchester Coding), ControlNet, Data highway, Profibus, World FIP, Fieldbus Foundation, ArcNet, LONWorks, ASI, InterBus, Hart, and any other network utilising serial protocols with SOF and EOF.
  • Ethernet Manchester Coding
  • VAN enhanced Manchester Coding
  • ControlNet Data highway
  • Profibus World FIP
  • Fieldbus Foundation Fieldbus Foundation
  • ArcNet ArcNet
  • LONWorks ASI, InterBus, Hart, and any other network utilising serial protocols with SOF and EOF.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Small-Scale Networks (AREA)

Abstract

Un appareil de mesure de la charge de bus prévu pour un réseau de zone de contrôleur (CAN) comprend un émetteur-récepteur (10) qui convertit un signal CAN entrant en un signal numérique standard (TTL). Un compteur (20) est prévu pour capturer le début de trame (SOF) et la fin de trame (EOF) du signal en calculant le nombre de bits récessifs présents avant un bit dominant (pour déterminer le début de trame) et après un bit dominant (pour déterminer la fin de trame). L'appareil de mesure comprend un convertisseur de trames de message (30) qui est déclenché par la réception d'une impulsion de début émise par le compteur (20) pour commencer le comptage. Ce comptage prend fin dès réception d'une impulsion de fin émise par le convertisseur (30) qui est fournie à un voltmètre (40) assurant une indication visuelle du chargement du bus en pourcentage. Le convertisseur (30) est commandé par un commutateur de fréquences (32) fourni par un oscillateur à quartz (34).
EP98952859A 1997-11-08 1998-11-05 Appareil de mesure de la charge de bus utilisant un detecteur d'enveloppe numerique Withdrawn EP1031209A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9723557 1997-11-08
GBGB9723557.6A GB9723557D0 (en) 1997-11-08 1997-11-08 Bus loading meter
PCT/GB1998/003316 WO1999025097A1 (fr) 1997-11-08 1998-11-05 Appareil de mesure de la charge de bus utilisant un detecteur d'enveloppe numerique

Publications (1)

Publication Number Publication Date
EP1031209A1 true EP1031209A1 (fr) 2000-08-30

Family

ID=10821733

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98952859A Withdrawn EP1031209A1 (fr) 1997-11-08 1998-11-05 Appareil de mesure de la charge de bus utilisant un detecteur d'enveloppe numerique

Country Status (4)

Country Link
EP (1) EP1031209A1 (fr)
AU (1) AU1040799A (fr)
GB (1) GB9723557D0 (fr)
WO (1) WO1999025097A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE533636C2 (sv) 2004-10-25 2010-11-16 Xinshu Man L L C Anordning vid bussförbindelse i CAN-system
EP1829294A1 (fr) * 2004-10-25 2007-09-05 Kvaser Consultant AB Dispositif pour systeme can
US7818603B2 (en) 2007-03-28 2010-10-19 Microsoft Corporation Deriving accurate media position information

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2577368B1 (fr) * 1985-02-12 1987-04-17 Electricite De France Dispositif d'analyse de trafic sur reseau local de transmission de donnees
WO1993022857A1 (fr) * 1992-05-04 1993-11-11 Ford Motor Company Limited Circuit asservi de commande de bus pour les communications de classe a dans un vehicule a moteur

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9925097A1 *

Also Published As

Publication number Publication date
WO1999025097A1 (fr) 1999-05-20
GB9723557D0 (en) 1998-01-07
AU1040799A (en) 1999-05-31

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