pattern generation and acquisition loopback

[Siddu 140]

Hi,
 
I am working over the NI DIO 32 HS 6534 card for the first time. One of my program in my application over the card is to run a loop back test using buffered configurations. I want to transmit a buffered pattern from one port and read it back through another port using the internal clock reference and verify that the data received is the same as data transmitted. I am able to do that perfectly at lower update rates (below 10000 updates/sec). But when i try the same at higher update rates i either miss out some data or read some junk data. I am unable to synchronize the configurations. I have to do this test at higher update rate ( >= 4Mhz). Attached is the example code which i tried and which works for lower update rates. Please help me out solving the problem.
 
Regards,
Siddu


Loopback.vi:
http://forums.ni.com/attachments/ni/70/3339/1/Loopback.vi

[Sean C.]

Hello Siddu,
 
Can you run the example VI at: <a href="http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B123AE0CB94D111EE034080020E74861&amp;p_node=201229" target="_blank">http://sine.ni.com/apps/we/niepd_web_display.display_epd4?p_guid=B123AE0CB94D111EE034080020E74861&amp;p_node=201229</a>&nbsp;?&nbsp; This example demonstrates how to synchronize the Digital Input and Digital Output tasks.&nbsp; If you can run the example (even at the high speeds) then there is probably a problem with your code.
&nbsp;
Please let me know your results.
&nbsp;
Regards,
Sean C.

[Sean C.]

Hello Siddu,
&nbsp;
I modified your code&nbsp;a little, and was able to get very good results up to 3.33 MHz.&nbsp; Will this be fast enough for your application?&nbsp; If you try to do this at rates of higher than 3.33 MHz, you will only read in every other sample.&nbsp; I have escalated this issue to R&amp;D and I am currently waiting on a response.&nbsp; I will let you know what I find out.
&nbsp;
Please see the attached VI for details about my modifications.
&nbsp;
Let me know if you have any further questions.
&nbsp;
Regards,Sean C.


Loopback[1].vi:
http://forums.ni.com/attachments/ni/70/3355/1/Loopback[1].vi

[Kip Leitner]

Hi,

I also am trying loopback on 6534, using burst mode and internal
clock.&nbsp; I am running at 2 MHz.&nbsp; I am using DAQ-MX and visual
C++.&nbsp;&nbsp; I have successfully sent and looped back a&nbsp;
single burst of 16 Mbytes.&nbsp; However, the "number of samples read"
values that I get back from the 'digital read' function is always '0',
so that's wierd.... hmm..... But, the data is correct.

I would like to put this in a loop.&nbsp; Can you post the loop code,
C/C++?&nbsp; I'm happy to try it.&nbsp; Thanks for any help you may be
able to offer.

Sincerely,

Kip Leitner &nbsp;