Pulse

Hi everyone.
How could I make a bipolar pulse(changes polarity every time) using VI examples on LabView 7.1?
I tried to manage it by using two VIs and by configuring it's duty rate and delay time.
I've checked it by using oscilloscope but it didn't work out.
I am feeling that VI's like "Generate Single Pulse Train" can't generate square wave from 0 V to under 0 V.
(for example, 0 to -5v square wave) In my case, it starts with 10v, then goes to 0v when setting the output polarity to negative.
Am I just confused or is there a way to solve this problem?
If anyone have an idea, please give me an advise.
I am using DAQ board for outputs.

Hello Mr. Kouim,
Thank you for your reply.
It looks like we're almost there! The problem you're seeing now is
that the two counters are starting out-of-sync. You'll need to
synchronize the counters by sharing the start trigger. A good sample
to start with is:
Sample Finder>Hardware
input output>>DAQmx>Generate Digital Pulse Signal (Counter
output)> Gen Dig Pulse Train-Continuous-Dig Start.vi
Modifying the above to work with two counters will enable you to start
both counter outputs in-sync using an external trigger signal.
For your reference, I've made a simple program that does this. Please see the attached file.
Thank you,
Daisuke Arase
Applications Engineer
National Instruments Japan
Attachments:
sync 2 counters.vi ‏111 KB

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UPDATE:
I was able to work around my problem for the moment by symlinking the configuration file to the location that pulseaudio was actually looking for it
# mkdir -p /usr/share/alsa/ucm/HDA\ Intel
# ln -s /usr/share/alsa/cards/HDA-Intel.conf /usr/share/alsa/ucm/HDA\ Intel/HDA\ Intel.conf
Although this does get my sound back, it is a hacky work-around and obviously not ideal. Anyone who knows a bit about pulse configuration, I welcome your input here
Last edited by OakRaider4Life (2013-04-14 22:14:34)

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signal generator.vi ‏78 KB

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Message Edited by awais.h on 03-30-2010 11:20 PM
Message Edited by awais.h on 03-30-2010 11:21 PM
Solved!
Go to Solution.

Hi
Thanks for the code but I'm afraid it won't work. Like you said the probability of choosing a value that is on both graphs may not happen. This is something that I would like the code to do automatically.
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Attachments:
peak_find_screenshot.jpg ‏45 KB

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How can I use the pulse train from a 6602 to trigger an niFGEN and niSCOPE on each rising edge of the pulse train?

Hello,
Here is my application: I need to use a 6602 counter/timer to generate a pulse train of certain frequency and duty cycle. On each rising edge of this pulse train, I need to output an arbitrary waveform on Ch. 0 of an niFGEN (5422) AND acquire data from CH. 0 of an niSCOPE (5124). I also need to synchronize the niFGEN and the niSCOPE to the same clock used for the pulse train (6602/ctr0). This process needs to continue until the user stops the system.
I can generate the pulse train using the 6602 just fine using ctr0, but the pulse train shows up on OUT0 by default. When setting up the niFGEN and niSCOPE to trigger on rising/positive slope edge, OUT0 is not an option for either device as a source for the digital rising edge (pulse train). The main options for both are PFI0-3 and RTSI lines.
Questions:
1.) Is there a way that I can direct the pulse train to a location (such as an RTSI line) where BOTH the niFGEN and the niSCOPE can use it as a start trigger for each rising edge? I noticed in MAX that a route can be made between ctr0's internal output and a trigger line and others. If this is a solution, could you please explain how to accomplish this?
2.) Once I configure the niFGEN and niSCOPE to be triggered on a digital rising edge, how can I effectively have this happen for every rising edge from the pulse train? In other words, can I just initiate the FGEN outside of the while loop and it will generate a waveform for each rising edge it sees at the source until the while loop is exitted?
3.) Is setting a reference clock for the niFGEN and the niSCOPE the same thing as synchronizing both devices using the same clock that generated the pulse train? It is not clear to me the difference, and why it would necessarily be useful.
Images of my current front panel and block diagram are attached. If you would rather have the actual VI's just let me know. Any help and/or explanation on this is greatly appreciated. Thanks in advance.
Attachments:
Front_Panel_Control.jpg ‏278 KB
Block_Diagram_Control.jpg ‏263 KB

Hello Cgifford,
Welcome to National Instruments Forums.
To output your signal to the PFI lines,
you can use external connectios between OUT0 and PFI lines. You can also use
the backplane to do so by routing into the same RTSI line.
1)
On the SCOPE and FGEN, the name of the
terminals are actually “PXI Trigger Line x/RTSIx” but on the 6602 you might
need to route the signal using the property:
You can also use the DAQmx route signal which perform the same opperation.
2)
This will depend on the frequency of
your pulse train. If this is lower than about 10 ms, then you can probably
place this on a loop and start and stop the acquisition every time. If the
frequency is higher than this, you will have to use:
- Scripting on the FGEN side (read more)
- MultiRecord Fetch (more information in the scope help file
section “Acquisition Functions Reading versus Fetching”).
3)
The short answer is yes. The longer one
might depend on how tight you need the synchronization to be (us, ns, ps). For
very tight synchronization, you should look into here.
Message Edited by Yardov on 06-18-2007 03:14 PM
Gerardo O.
RF Systems Engineering
National Instruments
Attachments:
property.JPG ‏7 KB

PCI 6602:How can I use the digital lines of the board and in the same time to generate pulse train using a counter?

Hello!
My problem appeared when I tried to update my code from Traditional NI-DAQ Legacy to DAQmx.
I am using 2 counters (counter 5 and counter 7) from PCI-6602, to generate pulse train, and also the Digital I/O lines of the port 0 (the lines form 0 to 7). What I do in my application is that I am starting to generate the pulse train on the output of the 2 counters, and after that I am playing with the state of the digital lines.
In traditional there was no problem using the counters and the digital lines in the same time, everything was going perfectly, but in DAQmx this is not possible.
What happens: I start to generate pulse train on the output of the counters, no errors encountered, but when I try to modify the state of one line of the digital port the generation of the pulse train is stopped. This is happening when I start the task associated to the digital port.
My question is: it is possible to create a channel on the digital lines without altered the channels created for the counters?
Another thing what I manage to see using the "Measurement & Automation Explorer" and Test panels for PCI-6602, basically is the same thing, I generate pulse train on the output of the counter 7 and try to start a task on the digital line, but I get one error :
"Error -200022 occurred at Test Panel
Possible Reason(s):
Measurements: Resource requested by this task has already been reserved by a different task.
Device: Dev4
Terminal: PFI8"
Instead if I use the counter 0 or counter 1 to generate pulse train I don't encounter the same problem.
Which resources are used by the counters 2 to 7 from the PCI-6602 board and the counters 0 and 1 do not use?
Thank in advance for any replies!
Ciprian
Solved!
Go to Solution.

Hello Jordan, thank you for your reply.
I am sorry but I can not see or run your example, I don't use LabView, I use Visual C++ for developing.
Here is the code for generating the pulse train:
GeneratePulseTrain(unsigned long ulCount1, unsigned long ulCount2)
    short nStatus = 0;
    nStatus = DAQmxCreateTask("",&m_taskHandle);
    nStatus = DAQmxCreateCOPulseChanTicks (m_taskHandle, "Dev4/count5", "", NULL, DAQmx_Val_Low, 0.0, ulCount1,ulCount2);
    if( bTriggerMode == true) // if hardware trigger is enabled
       nStatus = DAQmxSetTrigAttribute (m_taskHandle, DAQmx_ArmStartTrig_Type, DAQmx_Val_DigEdge);
       nStatus = DAQmxSetTrigAttribute (m_taskHandle, DAQmx_DigEdge_ArmStartTrig_Edge, DAQmx_Val_Rising);
       nStatus = DAQmxSetTrigAttribute (m_taskHandle, DAQmx_DigEdge_ArmStartTrig_Src,"Dev4/PFI17" );
   //set the internal timebase
   nStatus = DAQmxSetCOCtrTimebaseSrc(m_taskHandle,"Dev4/count5","20MHzTimeBase" );
   nStatus = DAQmxStartTask(m_taskHandle);
    return nStatus;
And the code where I try to set the digital line:
SetChannelState(short nState)
    short nStatus = 0;
    uInt8 wrtBuf0[1]={0};
    nStatus = DAQmxCreateTask("",&m_taskHandle);
    // Configure line as output
    nStatus = DAQmxCreateDOChan (m_taskHandle, "Dev4/port0/line0", "", DAQmx_Val_ChanPerLine);
nStatus = DAQmxStartTask(m_taskHandle);
    wrtBuf0[0] = nState;
    nStatus =DAQmxWriteDigitalLines (m_taskHandle, 1, 0, 0, DAQmx_Val_GroupByScanNumber , wrtBuf0, NULL, NULL);
    nStatus = DAQmxWaitUntilTaskDone(m_taskHandle,10);
    nStatus = DAQmxStopTask(m_taskHandle);
    nStatus = DAQmxClearTask(m_taskHandle);
    m_taskHandle = 0;
    return nStatus;

Pulse

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