compact-DAQ NI 9178 and USB3

[A._Dek...]

Hi,

I'm using a system based on a cDAQ 9178 (with 2 NI 9223 + 1 NI 9401) with a sampling frequency at 1MHz (the maximum rate).

Using USB3 ports, my application was not able to read the samples on time : buffer overwrite error

Using USB2 ports, everything was fine...

DAQmx version : 9.9 (delivered with the devices)

LV 2011 (run-time)

I don't find any information on NI website. Did anyone also notice this point ?

I didn't check the USB 3 performances, but just used the USB2 instead.

Best regards,

Adeline.

[Jerry_X]

Adeline, may you specify which error code you were seeing? -200361 overflow or -200279 samples no longer available? It sounds like you are getting the second error but I just want to make sure because they are very different scenarios.

-200361 overflow signifies that due to system or bus-bandwidth issue the device can't stream the data back to the host fast enough to keep up; -200279 samples no longer available signifies that the device was able to stream the data back to the host buffer but the software application was not able to read the data out of the host buffer fast enough such that samples were being overwritten.

I have run into -200279 samples no longer available error plugging USB 2.0 device into USB 3.0 ports while running existing DAQ applications. This was on Windows 7 with a TI USB 3.0 host controller and host controller driver. The root cause I found in this case is that the TI host controller driver was putting a heavier load on the CPU versus the USB 2.0 host controller driver built into Windows provided by Microsoft. The increased CPU load causes my DAQ application to read less often from the host buffer every second, thus cause my DAQ application to not keep up. I found a way to work around this issue by increasing the size of host buffer that DAQmx uses and increasing the number of samples read.

[A._Dek...]

Hi,

thanks for your reply.

In fact, I don't have the devices anymore, so I can not test again and I don't remember which error it was exactly.

It was under Windows 8.1, Intel chipset (but I don't remember which model exactly)

I optimized the DAQmx buffer size and the number of samples read when I developed the application 2 years ago.
Indeed, the system using 1MHz as sample frequency, it's quite high... and due to some problems, I tested several things. But finally, I reached the requirements.

This time, I simply worked around the problem by using the USB2.0 like in the previous system.
In fact, I posted more to share this point in the forum, for further users.

I hope that NI is planning to migrate all their compactDAQ and RT controller to USB3 soon...

Best regards,

Adeline.