How to Get Fast RT/XP Ethernet Comm.s?

Question

I have an application where I need to do the following between an XP
computer and a PXI-8187 RT computer:
1. Send a small set of values (<100 bytes) from XP to RT.
2. Send a small set of values (<100 bytes) from RT to XP.
3. Send a large I16 array (20,000 size or 40kbytes) from RT to XP.
My RT loop rate needs to be 20 Hz. The XP loop rate can very but I cannot
miss any of the 20k I16 array.
I started out by using DataSocket but it was much too slow. My next step
was to do number 1 & 2 above using UDP. This was simple and works fine.
Unfortunately, RT cannot presently send UDP packets that are greater than
4096 bytes at one time so I could not use UDP to send the I16 array.
I then setup TCP/IP and RT FIFO parallel loops to send the I16 array but it
isn't working very well. I setup my FIFO to be 80x 20kI16 arrays which
should be four seconds of data. When I run my program my TCP transmit loop
loses some of the packets from the RT buffer. I will get good data for a
second or two and then loose around 20 packets and this will then repeat
every few seconds but the time it works is not consistent. I'm not sure if
my problem has to do with the RT FIFO or the Ethernet communications. I did
setup a test VI that did not have the RT FIFO in it and did not lose any
data but this only works if I can guarantee that the XP computer can keep a
consistent 20Hz TCP/IP loop and this would be too risky. Note that I did
not use the RT Communication Wizard to setup my program but I did use it to
create a similar example to look at. My XP monitor shows LAN utilization of
only 0.4% max and my XP CPU usage is only around 10%.
Does anyone have any ideas of why I can't get consistent data at the speed I
am trying for?
Does anyone have a better network communications approach to do what I am
trying to do?

Answer 1

Would something like this work?  It is 8 channels at 33kSa per second per channel from a 200Mhz RT controller
http://sine.ni.com/nips/cds/view/p/lang/en/nid/202103
The source code for this is at:
http://zone.ni.com/devzone/conceptd.nsf/webmain/3F941A040879E64086256FA20067041A
It uses the command server architecture
Preston Johnson
Principal Sales Engineer
Condition Monitoring Systems
Vibration Analyst III - www.vibinst.org, www.mobiusinstitute.com
National Instruments
[email protected]
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