Synchronizing the NI PXI-4472 with E Series Analog Output in Traditional DAQ

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Note:
This example uses Traditional DAQ VIs. We recommend the use of DAQmx VIs with these devices. See link below for examples.
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This example program illustrates hardware synchronization between NI PXI-4472 dynamic signal acquisition (DSA) devices and E Series multifunction data acquisition (DAQ) devices. In this example, the multifunction DAQ devices provide analog output rather than input.

The synchronization is not as straightforward as synchronizing a pair of E Series devices. The NI PXI-4472 routes its oversample clock on the PXI_Star line, while the E Series device uses a Real-Time System Integration (RTSI) bus line for an output update clock. One of the general purpose counters on the E Series device divides down and redirects the DSA oversample clock so that the E Series device can use it.

The DSA oversample clock runs at 256 or 128 times the DSA sample rate, while the E Series device requires a slower clock at exactly the update rate. The counter source is RTSI 6, another name for the PXI_Star line carrying the DSA oversample clock. The counter divides this signal down by the correct ratio and outputs a slower E Series device update clock to a standard RTSI line. Because the divide-down ratio can, in principle, be any number, the E Series and DSA devices can sample at different rates while maintaining synchronization.

This synchronization scheme does not work for DSA and E Series devices for the PCI bus. The reason for this is that the PCI DSA device uses a special RTSI line that cannot be "seen" by a counter.

Using the Software:

-- Make sure your PXISYS.INI file is configured correctly. To do this, launch MAX and display the list of devices and interfaces by clicking the + symbol next to the Devices and Interfaces icon. You should see the NI PXI-4772 in the device list. Highlight the NI PXI-4472 which is physically located in slot 2 of the PXI chassis. Look in the frame on the right side of the screen which lists the PXI slot. The slot should appear as "2". If it appears as "0", you probably have a problem with the PXISYS.INI file, or it is not present. If you are using a PXI controller, copy the appropriate PXISYS.INI file to the top level of the Windows or WINNT folder. If you are using MXI-3, please refer to Knowledgebase 2CFE965P, linked below, to fix your PXISYS.INI file:

-- Set the device numbers appropriately. If you have only one DSA device, the master in slot 2, you should empty the array labeled DSA Slave Devices.

Fill in the array labeled PXI Slot Numbers for DSA and MIO slaves. This array should contain the physical PXI slot numbers for all DSA and E Series devices except the NI PXI-4472 in slot 2.

-- Run the program. You should see time domain data from the DSA device at 50 kS/sec and the E Series device at 100 S/sec. This is intended to represent sampling rates that might be used for accelerometers and thermocouples, respectively.

-- If you change any of the sampling parameters, check to be sure that the value in the box labelled ratio of total acquired points is a whole number. If it is a fractional number, a scan backlog will slowly build on either the DSA or E Series device, eventually producing a buffer overrun error. Setting the DSA and E Series device at the same scan rate works without problems. In general, you should have no difficulties when the sample rate of either the sample rate of the DSA or E Series device is evenly divisible by the other.

Related Links:

Knowledgebase 2CFE965P: PXISys.ini File

KnowledgeBase 3EE7N2NQ: Synchronizing DSA Devices with DAQmx

Requirements

Filename: 202808.llb

Software Requirements

Application Software: LabVIEW Full Development System 6.1
Language(s): LabVIEW

Hardware Requirements

Hardware Group: Multifunction DAQ (MIO)
Hardware Model: DAQCard-6023E, PCI-4472
Driver: Traditional NI-DAQ (Legacy) 6.9.3

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