Overflow error cRio NI9222

Question

Hi All
I'm trying to program a cRio 9068 to record data from two synchronised NI 9222 cards, all channels sampling at 500kS/s.  I've been playing around with Labview FPGA and I've managed to read data from the cards, however I've started getting an overwrite error which I'm having issues solving.
I've based my FPGA code on examples in LabView reading NI9222 cards. I have the host vi reading from two Read FIFOs - one reads the number of remaining elements and then the other reads those elements and sends them off to an array which currently doesn not do anything. It all seems to work OK until I start to set the sample rate to around 500kS/s. I then to begin to get overwrite errors and I haven't been able to figure out how to get round the problem.
What's worrying me is that I might have come across a fundamental limit of the cRio- too many samples per second? I've tried to set the 'Requested Number of Elements' in the FIFO properties dialog to 8192 but that flagged up an error in compiling the FPGA. Anyone have any ideas? I'm fairly new to this so would not be surprised if I've done something relatively stupid.
Code is attached.
Cheers
Attachments:
NI_9222_Anologue_DAQ2_FPGA.vi ‏179 KB
NI_9222_Anologue_DAQ2_FPGA.vi ‏179 KB
cRio_Project_2.lvproj ‏42 KB

Answer 1

Hi Maria
Thanks for your reply. To answer your questions:
1) It seems that things are relatively stable at one sample every 4us. Once set to 1 sample every 2us then the FPGA stops working and I get the overwrite error. One thing I have recently noticed is that I have two possible options for selecting the FPGA (see attached pic). If I select RIO0 in the drop down menu of my host vi things are a bit more stable than if I select rio://169.254.232.241/RIO0. Is there an explanation for this- I assumed these were the same thing?
2) I have tried using four channels and everything seems to work OK. Due to the time it takes to compile the FPGA I haven't tried all channels but with 5 channels at 2us sampling things would still fall over every now and then.
3) I am trying to build an application which records 8 channel raw .wav files at 500kS/s. The cRio will be placed in an autonomous buoy, deployed at sea and used to record the vocalisations of harbour porpoises from an array of 8 hydrophones. The reason I must sample at 500kS/s is that harbour porpoises vocalise at 120-150kHz and so sample rates of at least 300kS/s are needed- higher is much better and 500kS/s is the research standard. I'm hoping to convert the FPGA bitfile to a C API so I can program the cRio in eclipse, however I thought it better to get everything working on LabView first.
Attachments:
cRio Pic.jpg ‏367 KB