sampling simultaneously on pci express 7841r with pci 6255 and pci 4462

[guillaumegarreau]

hi all,

i am working on a project what aim to sampled several different analog signals at different frequencies. the basic systems is with pic microprocessor and adc on pcb but as the deadline is next week and some of the pcbs are not ready, i've been told to develop a solution using labview and NI acquisition cards.

the  systems is: 9 channels for seismic sensors (4.5Hz to 10Hz signals), 4 microphones for acoustic surveilliance unit (ASU) and 2 pairs of channels for mannequin and gerbils (kind of rats) microphones.

For the mannequin and the gerbil we use a NI PCI 4462, as the mannequin needs a current source to biase the microphones and we want to sampled up to 14KHz signals (the 4462 sampled at 204.8KHz).

the the 13 others channels the easy solution is to put all of them on the NI PCI 6255 and sample at the max frequency (750kHz/13) but this has a double disavantage:

1-the first is to use a unnecesary high sampling frequency for the seismic signals that means creating a bunch of data not needed

2-the 2nd is that we reduce the info bandwith for the ASU,

the solution was to use the NI-PCIe 7841r to sampled the ASU signals at 200kHz and use the 6255 for the seismic (sampled at 100Hz),

my problem is to sample simultaneously the 3 different cards, especially using the fpga in the same VI than the 2 other DAQmx...

anyone knows how to do it, or even if it is possible?

one more thing, i started to use labview a week ago...

thx in advance for any help

[jareds]

Hi,

It sounds like the three different cards are going to be sampling at different rates.  Is that correct?  If they are, then you should simply synchronize the start of all three operations using RTSI lines or external trigger signals.  This article describes how to synchronize with a 4462.

The VI which will be running the FPGA won't be able to have the DAQmx VIs in it.  This is because it will be running on the 7841r itself, while the DAQmx functions must be run on your computer's processor.  You can, however, interact with the FPGA VI running on the 7841r using the FPGA interface VIs.  You can find a general resource about FPGA programming here.