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daqmx triggering

I've poked around the KB a bit and didn't see anything related to my seemingly easy problem regard triggering with my PXI-6533. My device is named "Dev3" and the line I'm polling for a waveform is "Dev3/port0/line3". I want to trigger off of this same line to start my waveform but the only available options for the trigger source are PFI and PXI_Trig lines. I've attached a screen shot of my VI and of the source options for triggering. I'm using LabVIEW 8.6.



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Have you looked at the manual/pinout for the device? I couldn't find a manual but it normally tells you which lines are PFI lines - it maybe the the line P0.3 is a PFI line. For example on the 6211, P0.0 is PFI0


Hope this helps




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Message 2 of 8

Found the specs. The PFI lines are categorized as "control lines". I didn't expect to have to wire my signal into two separate inputs. I will try to wire one of the PFI lines at work tomorrow.

Digital Lines and Ports

The 32 individually configurable lines of digital input and output on the NI 6533/6534 are grouped into four 8-bit ports, as shown in the following table. Dev1 in physical channel names is the default device name for NI 6533/6534 devices. You can change these names in Measurement & Automation Explorer (MAX).

Port NI-DAQmx Physical Channel Name (Lines) NI-DAQmx Physical Channel Name (Ports)1
Port 0 Dev1/port0/line0Dev1/port0/line7 Dev1/port0
Port 1 Dev1/port1/line0Dev1/port1/line7 Dev1/port1
Port 2 Dev1/port2/line0Dev1/port2/line7 Dev1/port2
Port 3 Dev1/port3/line0Dev1/port3/line7 Dev1/port3
1This physical channel name refers to all eight lines in a port at once.

For Ports 0 through 3, you can configure a port width of 8, 16, or 32 bits. To configure a 32-bit port, use the physical channel name Dev1/port0_32. To configure a 16-bit port, use channel names that refer to all the lines in multiple consecutive ports: Dev1/portP_N, where P is 0 or 2, and N is the total number of lines. For example, to combine Port 2 and 3 into a 16-bit port, you would specify Dev1/port2_16 as the physical channel.

Control Lines

The NI 6533/6534 has two timing controllers (Group 0 and Group 1) for high-speed data transfer. Each group contains four control lines which can time the input/output of data with hardware precision. You can use Groups 0 and 1 to perform the following actions:

  • Generate or receive digital patterns and waveforms at regular intervals or timed by an external TTL signal
  • Transfer data between two devices using the handshaking or burst sample timing type
  • Acquire digital data every time the state of a data line changes (the change detection sample timing type)

Configuring Unused Control Lines as Extra Data Lines: Ports 4 and 5

If you are not using Group 0 and/or Group 1 as timing controllers for timed operations, you can use their control lines as extra data lines. These lines constitute Ports 4 and 5. The direction of these lines is not configurable—four lines are used as input only (Port 4), and four are used as output only (Port 5). On a per line basis, Port 5 lines can be configured for open collector generation.

Even though there are eight actual lines, the port widths are 4 bits. The following table shows the lines that make up Ports 4 and 5.

Direction Line Group I/O Pins Physical Channel Name (Lines)
Input 0 0 PFI 0 Dev1/port4/line0
1 1 PFI 1 Dev1/port4/line1
2 0 PFI 2 Dev1/port4/line2
3 1 PFI 3 Dev1/port4/line3
Output 0 0 PFI 4 Dev1/port5/line0
1 1 PFI 5 Dev1/port5/line1
2 0 PFI 6 Dev1/port5/line2
3 1 PFI 7 Dev1/port5/line3
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Message 3 of 8

I put a jumper on my signal wire so it is now going into Dev3/port0/line3 as well as /Dev3/PFI0 for my trigger. DIO acquires signal fine until I insert the trigger VI. Now DAQmx Start Task is erroring out with


"Error -200904 occurred at DAQmx Start

Possible reason(s):

Measurements: Start Trigger Type requested is not supported given the requested Timing Type.  

To use the requested Timing Type, do not set the Start Trigger Type property. NI-DAQmx automatically selects a compatible Start Trigger Type setting.

To use the requested Start Trigger Type, select a different Timing Type.

Property: SampTimingType
Requested Value: On Demand

Property: Start.TrigType
Requested Value: Digital Edge

Task Name: _unnamedTask<31>"

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Message 4 of 8

Hello Andrew, this is Paul with Applications Engineering at National Instruments.


Just to be sure, you want to trigger a digital input off of itself, correct?


The best way to tackle this is going to basically be what you have already started on by using jumpers between the 2 lines.  It may be possible to achieve this through internally rerouting the signal, and only using 1 hardware input, but this will likely create problems and be more complex.


We actually have a shipping example that demonstrates what you are trying to do.  You are going to want to use a technique we call acquiring pre-trigger samples in order to ensure that your acquisition start coincides with the trigger, and that you don't miss samples in the delay.  Essentially by pre-triggering we are setting up your device to read trigger samples ahead of time, sort of as a buffer, to ensure that we don't lose your actual data samples.


In this example will need to use both a DIO line as well as that PFI line with a jumper as you are already doing.  To get to the example, in LabVIEW, please go to Help>Find Examples>Browse>Hardware Input and Output>DAQmx>Digital Measurements>'Read Dig Chan-Int Clk-Dig'


Let us know how that works out for you, and if we can be of more assistance.




Paul Davidson
National Instruments
Product Owner - Chat
Message 5 of 8

the valid start trigger sources for the PXI 6533 are PFI6 and PFI7.  Since your using PFI0 you get your error

PXI 6533 help

"Should be" isn't "Is" -Jay
Message 6 of 8

What Jeff said is also true, I missed this when looking through your documentation, although I would still recommend using pre-trigger samples (with PFI 6/7) to ensure that you don't lose any of your original signal.

Paul Davidson
National Instruments
Product Owner - Chat
Message 7 of 8


@Paul-D wrote:

What Jeff said is also true, I missed this when looking through your documentation, although I would still recommend using pre-trigger samples (with PFI 6/7) to ensure that you don't lose any of your original signal.

Someones gotta keep the blue bars honest! Smiley Very Happy


"Should be" isn't "Is" -Jay
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