DAQmxErrorOutputFIFOUnderflow2 -200621

[dduta41]

Hello,

I'm using a PXI1056 with PXI6652 connected to my PC via MXI connection.  I connected up to 8 PXI-4461 . When I running 7 PXI-4461 I have no issue but adding the eighth one generate  (DAQmxErrorOutputFIFOUnderflow2 -200621).the practical effect:  My SRC is generating not all samples and stop a few ms after.

Each PXI-4461 is triggered via the SMB on a rising or falling edge of a signal.

is there a technical limitation for getting a such number of PXI4461in the chassis 1056. Please note also if I running all the 4461 at low frequency ( digitizer and source), I have no error.. but as soon as I run around 120kHz the digitizer , it generating  this error.

the same PXI 4461 running alone  is working perfectly

Any feedback is welcome

regards,

[Andrew.M]

Hi Dduta41,

Have you tried out that slot of the 1056 to make sure it is working properly? Where is the 6652 located in the chassis? How are you configuring your synchronization of the modules?

Regards,

[dduta41]

Andrew,

the PXI4461  that generating this error is on slot18 . It's working fine alone and with other 6 additional PXI it is working also perfectly ,When I add 1 more ( total of 😎 that the sources of the 18 stop to work after a few ms

the MXI module is on slot one, 6652 on slot 2, then all PXI4461 are in slot 4,3,9,10,11,16,17,18.  A different arrangement such 4,3,5,6,7,8,9,10 for the PXI4461 might help ?.

I added a new computer and this message is occurring at higher frequency for the source and digitizer. Adding additional RAM up to 2G might help also  ( 1 have 1G for now)

Regards

[Robert__R]

dduta41,

It sounds like you're running into bandwidth limitations.  Output is much less efficient on the PCI bus, so that's going to be the weak link.  There may be some software things to try (like buffer sizes), but here's some stuff from the hardware perspective.

Put the boards as close to the controller slot as you can.  Slots 2-4 are best, slots 5-11 are intermediate, and slots 12-18 will get the lowest bandwidth.  These correspond to the 3 PCI segments in the 1056 chassis.  Your suggestion of rearranging the cards should help.

Are you using MXI-4 or MXI Express?  MXI Express will give you more bandwidth, so an NI PCIe-8361 and an NI PXI-8360 will do better than MXI-4 because the PCIe fabric is faster and more efficient for the host link.

How close are you to your target sample rate?

- Robert

[dduta41]

Robert,

I  will try some software trick as the buffer. As previously mentioned moving the module on  slot 5 to 11 might help . I'am using MXI4, to use MXIexpress, I need to change the chassis and the PXI4461 is not PXI express, meaning that I need to change my configuration.

Regards,

[Robert__R]

dduta41,

I'll be interested to hear how much improvement you get from changing slots.  Is it close to what you need for your application?

To clear up a misconception, there are several versions of MXI Express.  The NI PXI-8360 is compatible with your chassis (not to be confused with the NI PXIe-8360, which is not).  If you need a little higher sampling rate you may want to consider it.

Good luck.

- Robert