iPaq5550 & DAQ6062E - Time delay through WLAN transmission

[cornenemy]

Hello LabVIEW gurus!

Problem Description:

Actually, I work on a VI for a PDA (iPaq5550 & DAQ6062E) for a data acquisition of 16 channels (@100Hz) and a following transmission through a WLAN-connection (TCP/IP) to a client. In more detail, between the DAQ and the received data at the client there is a time delay of about 2.5 to 3 seconds which I wasn't able to solve. I tried to reduce the source code to a rudimentary construction where only the raw data of the 16 channels (INT16 values, 1D-array, 100samples/channel) was sent one time per second directly over the network connection. There was no parallel file writing process, graphs or anything else.

Questions:

1. Is it possible, that the problem occours because of the performance of the used PDA in combination with a multichannel DAQ?#

2. Do you know a method to reduce this time delay to guarantee a "live" preview of the data e.g. on a laptop?

3. What network protocol should I use instead of TCP/IP?

Thanks a lot for anwering my question(s)!

Greetings from Vienna,

Philipp Kornfeind
University of Vienna
Institute of Sport Science
Section of Biomechanics, Kinesiology and Applied Computer Science

[Ingo_Schumacher]

Hello Philipp,
here are some ideas concerning your questions:

1) Sure, the hardware performance can be a reason for this delay. But quite often it is also that the program is resource consuming. I would try to program this application based on a Producer/consumer design pattern. And try to play around with the DAQ parameters. Increasing the block size of the data to be read can save performance as well.

2)There is no golden ruel - or method I could recommend in general. It depends pretty much in the way you program (see hints above)

3)You could try UDP as an alternative - it is taking part of the handshaking and error checking - maybe this is increasing your transmission rate.

regards