View Full Version : Flock of Birds and EMG data sychronization summary

Brad Lawrence
08-07-2000, 01:45 AM
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
Email: Andrew.Pinder@hsl.gov.uk
Tel +44 114 289 2594; Fax +44 114 289 2526
HSL home page: http://www.hsl.gov.uk/
HSE home page: http://www.hse.gov.uk/hsehome.htm

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
http://www.skilltechnologies.com. 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

Website: http://www.skilltechnologies.com

My email: terry@skilltechnologies.com
General email: skill@skilltechnologies.com

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. (Ljohnson@innsport.com ;
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 http://www.innsport.com/prod02.htm. 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 skilltec@skilltec.com.

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:
www.innsport.com 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

To unsubscribe send SIGNOFF BIOMCH-L to LISTSERV@nic.surfnet.nl
For information and archives: http://isb.ri.ccf.org/biomch-l