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Flock of Birds and EMG data sychronization summary

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  • Flock of Birds and EMG data sychronization summary

    Thanks to those who responded.

    Brad Lawrence

    Original message:


    Currently, in our lab we are collecting Flock of Bird data via an
    Ethernet connection, and EMG data on a second system/platform via a
    standard A/D card. The FOB cards seem to be customized to only collect
    the motion data. The A/D system which is flexible to collect data using

    multiple channels is not compatible with the FOB system (in both
    hardware and software).

    Has anyone collected Flock of Bird motion data and EMG data at the same
    time? If so, how were the data acquired such that both signals were
    synchronized in time?


    Brad Lawrence
    North Carolina State University

    Response 1:


    I'm not familiar with Flock of Birds but my experience of similar
    problems tells me there are two issues:

    1: Statrting data collection simultaneously

    2: Ensuring the two set-ups remain in sync

    Prtoblem 1 can be dealt with by using a single switch to input
    pulses to start data collection into both systems simultaneously.
    You'll need a double pole switch to ensure the two systems remain
    electrically isolated. Just run one wire from one sid of the
    to the trigger input on one machine and a wire from the other side
    the switch to the trigger input on the other machine. (This
    you can start data collection with an externam trigger on both

    Problem 2 is not a problem if the clocks that control data
    are accurate enough that they don't drift apart. If this is a
    you might be able to input a single external clock pulse into both

    You will also need to select an EMG sampling rate which is a
    of the sampling rate for the FOB otherwise the two data sets won't

    Andrew Pinder, PhD, MSc, Eur Erg, MErgS
    Ergonomics Section
    Health and Safety Laboratory, Broad Lane, Sheffield, S3 7HQ, UK
    Tel +44 114 289 2594; Fax +44 114 289 2526
    HSL home page:
    HSE home page:

    Response 2:

    Dear Brad,

    I have a flock of birds system in my lab, and have successfully
    EMG and bird simultaneously using serial port interface. To do this, I
    use 2
    computers: 1) Flock of birds 2) National Instruments board for EMG. I
    trigger data acquisition on the second computer by opening and closing a

    serial port, (1 of 4) (using homegrown software) which sends a 9 volt
    pulse through one of the pins. I then use this pin to trigger
    acquisition on
    the a/d board. Then I send 2 more sync pulses through the serial port by

    opening and closing it twice. By simply opening and closing the port, I
    avoid software delays associated with writing data to the port. The
    thing works rather well.

    However, I should note that I am currently in the process of revamping
    system to use only one computer. For this system, I am using tektronics
    osscilloscopes to collect emg data. They can be controlled via serial

    The impetus for having off-line EMG collection has been that I use
    display feedback from flock data, which is CPU intensive. Thus, I don't
    the high speed EMG collection to interfere. I can give more detail if

    Response 3:

    Hi Brad, we were having the same problem, except it was motion star and
    force plate data. As I was told by Ascension: "if you have a flock of
    the jumpers need to beinstalled for the use of a TTL Pulse. In the FOB
    Manual page 9 it lists the jumper settings needed to enable the TTL
    function and on page 116 ust he SYNC mode command information." The
    if you don't have it, can be down loaded at the following ftp site:

    Hope this helps, and do post your replies.

    Angela J. Tate B.Sc.
    M.Sc. Candidate
    Dept of Mechanical Engineering
    Queen's University
    McLaughlin Hall, Stuart St.
    Kingston, Ont. K7L 3N6
    Phone: (613)-533-3060
    Fax: (613)-533-6489

    Response 4:

    I am using Skill technologies software to do this. It is expensive, but

    allows you to collect FOB and A/D data simultaneously on one or two
    systems. I believe that you can also use a TTL out from the FOB to a
    trigger your a/d system to collect data whenever your FOB system is
    collecting data. Good luck.

    Warren Darling

    Response 5:

    My experience is that the FOB is too difficult to synchronize with other
    device, unlike Pulhemers. What we did was to use the CRT SYNC option
    provided by the Ascension and we generated our own SYNC signal by timers
    on the DAQ A/D card (National Instru.). In this way you can
    sychronize FOB with any signal sampled by the A/D card. But if you want
    to get exactly synchronized data point you should use STREAM MODE,
    because we found the CONTINEOUS POINT MODE gives you triple of the data
    points you want to get. And the FOB data should be shifted
    backward about 6ms (or maybe 5ms? I couldn't remember.) because its
    buffer gives data with such a delay. In this way, we could synchronize
    the FOB sometimes but not completely reliable. We gave up because we
    have no time to spend and people in Asension seems can not help
    anymore. What we do now is connecting the data transfer satrt signal (in
    RS232 cable) to one channel on the A/D card and sample it. Then at
    least we know when the Bird's data starts. Of course, we let the Bird's
    work at fixed frequency of 100Hz.
    Good luck. And if you finally fix the sychronization of FOB, kindly let
    me know.
    Amanda F. Lin, Ph.D
    Department of Physical Medicine & Rehabilitation/Rehabilitation
    Institute of Chicago
    Northwestern University Medical School

    Response 6:

    Hello Brad,

    Yes, the Skill Technologies Biomechanics Software (for Flock of Birds)
    can syncronize with analog systems (EMG, force plates, etc.) either
    through the Skill A/D
    package or through RUN Technologies' A/D. Visit our web site at If you have questions or need further
    information please contact
    me at your convenience.

    Terry W. Long
    V.P. of Marketing
    Skill Technologies Inc.

    Telephone: (602)277-7678
    Fax: (602)277-2326


    My email:
    General email:

    Skill Technologies Inc., "The True 3D, True Real-Time Motion Analysis

    Response 7:

    I have collected these type of data. I used a synchronization
    switch on a separate A/D channel to both the EMG and the Motion Star
    kinematic data. I suggest that you contact Lee Johnson from Innovative
    Sports Training Inc. ( ;
    were very helpful to me and have developed excellent software to address

    this problem among others.

    Leif Hasselquist
    Biomedical Engineering
    University of Iowa

    Response 8:

    Dear Brad,

    We produce The MotionMonitor(TM) for use in biomechanical, motor
    physical therapy and sports medicine research applications. This product
    designed to deal with the synchronicity issues of collecting data from
    Ascension trackers, video, A/D boards, forceplates and emg. It will
    data from each device at different measurement rates that you specifiy,
    synchronize that data, and play it back immediately. All data, raw and
    processed, can also be exported to other software packages. You can see

    details on this product at While
    product is normally sold as a turn-key product with all hardware, we
    sell the software stand-a-lone for installation with your hardware.

    The eathernet connection you purchased is really not the best interface
    use for research because of the latency involved in the TCP/IP protocol.

    The preferred interface is ISA. Our software will work nicely with the
    ethernet protocol but does require special switch assemblies to do so.
    you would like to discuss this in more detail please feel free to call
    me at
    the number below.

    Good Luck!
    Lee E. Johnson
    tel: 773-528-1935
    fax: 773-528-2149
    Innovative Sports Training, Inc.

    Response 9:

    I am much of the way into writing a LabView driver for the Flock of
    I have read Jimmy Abbas’ comments of 1996, and incorporated them into my

    programming. I have been able to auto configure for our four sensors,
    read from one sensor, and will continue to refine until all sensors can

    Two questions come to mind:
    1) What baud rates are being used for single RS232 systems, and how was
    2) Is the Flock of Birds being used where sensors cross the hemishere?
    Ascension said the rear hemisphere is not calibrated.

    Mark Bresler
    Research Scientist
    Center for Rehabilitation Technology
    Helen Hayes Hospital
    Rt 9W
    W. Haverstraw, N.Y. 10993
    (914) 786-4995

    Response 10:

    Dear Brad -
    I will be using both FOB and EMG in the future. I would like to know
    what kind of responses you get.
    Also, did you have any problems with signal interference from the
    magnetic field of the FOB? I expected it to be a major obstacle.
    Thanks -
    Janina Wilen

    :::::::::::::::::::::::::::::::::::::::::::::::::: ::::::::::
    Janina Wilen
    BioMechanical Engineer, B.S.
    Kessler Medical Research and Rehabilitation Corp
    Human Performance and Movement Analysis Laboratory
    West Orange, NJ 07052
    fax: 973-243-6984

    To answer your question, the magnetic interference occurs at very
    discrete frequencies on the EMG data (i.e. 120,240,360, etc.) which can
    be easily filtered, so it is not much of a problem. - Brad

    Response 11:

    I don't know the details about how Skill manages to do it, but I know
    they start up the FOB system, then wait a short period of time to ensure

    that it is active. Then they export a pulse that the A-D system uses as
    trigger to begin acquisition. They also record the time (or frame
    of the pulse in their system. Once you know that then you can
    the two signals. The people at Skill are quite helpful, so they may be
    to tell you what you need to know. You can call them at 602-277-7678, or

    email them at

    I'm sorry I can't be more helpful than this, but I hope this helps at



    Response 12:

    Dear Brad: I use the Skill software but have not yet checked that they
    synchronized. You should be able to use the TTL signal from the FOB to
    trigger data collection from the a/d board or use the event marker
    I bought something from Ascension for an event marker method, but I
    recall what it was. I have talked to people at Ascension previously.

    Warren Darling

    Response 13:

    Hello Brad,

    I had the same problem. I ordered a commercial package. It is the Motion

    Monitor and you can find more information on the following website: This software is capable of synchronising EMG signals,
    forcesignals and bird data. It is possible that your bird has to be
    configured for the software. But as far as I know it is the cheepest and

    easiest way for synchronising. There is also another company that is
    skill technologies. You can also find them on the internet. If you want
    information, feel free to ask.

    Best regards, Dennis

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