how to capture the waveform more faster or real-time form TDS220 osilloscope to PC via GPIB using LabVIEW

[fliablerain]

Now I am trying to use LabVIEW 8.20 to capture the waveform of the Tektronix TDS220

osilloscope(bandwith 100MHz,1GS/s Sample Rate 8-bit) to PC via GPIB interface card(PCI-3488,

Adlink technology inc. made in Taiwan, up to 1.5MB/s data transfer rates). I have installed

LabVIEW 8.20, NI VISA 4.1 (http://joule.ni.com/nidu/cds/view/p/lang/en/id/348) and

tktds2xx.llb(http://sine.ni.com/apps/utf8/niid_web_display.model_page?p_model_id=289). Now

It works well and I can get the answer form the osilloscope. But When I run the GPIB.VI in

LabVIEW example, I write "*IDN?", it read "TEKTRONIX,TDS 220,0,CF:91.1CT FV:v2.03

TDS2CM:CMV:v1.04" in less than 1second. When I use TKTDS2XX Getting Started 2.VI in

tktds2xx.llb to catch the whole waveform(2500 dots) displayed on TDS220 osilloscope, it

takes almost more than 8 seconds. Then I change to use wavestar(software for TDS220) to

capture the waveform via RS232, it also takes about 10 seconds. So I don't know why it takes

so long to transfer the waveform to PC when using GPIB. Can anybody help me to make it

faster and realize real-time control and capture?
Thanks for your attentions! Any comments will be appreciated!

[Dennis_Knutson]

First, there is no such thing as real-time control and capture with GPIB. It's simply not designed for that.

However, you can speed things up considerably by not calling the high level Getting Started every time. Look at the block diagram. with every call, it does the initialize which does the *IDN?, then it resets the scope, then it sets the vertical, horizontal, triggering, etc. before doing ana acquisition and then the transfer. I doubt that you have to do all of that every time you need a waveform. Just by looking at the block diagram, I suspect that all you have to do is call the Read Waveform to Array and the Scale Waveform Array functions. There might be commands in the Read Waveform to Array that might be skipped as well. I don't have a manual for this scope so I can't tell for sure. See if there is a section in your manual about high speed transfers. That will usually give you the minimum commands to acquire and transfer a waveform if you don't need to change any of the setups.