Multiple pulse generation off master, 6602

I would like to generate 4 pulse trains phased with respect to the master pulse train. The example vi I am working with shows phasing relative to the preceeding pulse train (counter), so changing the phase of only one channel on the fly requires rephasing all subsequent channels. I would prefer not to do this. This example uses a "counter group" of 2 and sets the nth gate to the n-1 output ("other counter output"). Can I use a larger counter group and refer all channel gates back to the master pulse train? In doing so would this alleviate the need to use the Route Signal vi in going from one counter group to the next? I am using an 8 channel, NI 6602 card.

I'd like to try to give you an answer, but I might first need to ask some questions:
A. Is the "Master" pulse train an external signal or something you are going to generate from the 6602?
B. You talk about phasing, so I assume that the other 4 pulse trains need to have the same frequency as the master -- is this correct?
C. Do you need both rising and falling edges to be phased to the Master, or only one of the edges?
Here's an outline for how to handle an external Master, where the other 4 pulse trains are at the same frequency but only the rising edges have the desired phasing relationship. (You could also do it this way for an internally-generated Master.) They will be directly referenced to the Master, so you can change the phasing on any one of them without affecting the others.
1. Physically wire the Master pulse train to a legal Gate input. (If your Master is internally generated you could use RTSI and save the screwdriver work.)
2. Program the other 4 counters to be in "retriggerable pulse" mode, using max internal timebase as a Source, and the pin from step (1) as a Gate. Program Gate polarity to be sensitive to rising edges. Output polarity can probably left as default (low state during delay or when inactive, high state during pulse). Each one has to be configured separately, using a unique group #
3. Program the pulse parameters to use for delay, and a minimal pulse duration. The short duration allows the counter to be ready to be re-triggered as soon as possible after the needed delay, allowing you to approach 360 degree lag.
4. It sounds like you already know how to pass in a new delay parameter "Pulse Spec 1" and issue the "Switch Cycle" command when you need to change the phase on the fly.
(If you have an internally generated Master where you can know the exact period, you could also have passed in the new pulse duration parameter "Pulse Spec 2" such that the sum is always == Master pulse train period. This way you can maintain phasing relationships on both rising *and* falling edges.)
However, if you have an external Master and need phasing on both rising and falling edges, I'm afraid I'm stumped.
Regarding "grouping" the counters: I don't think it can be done yet. But you can set up 4 individual counters with each one mapped to use the same physical signal for its programmed Gate (used here for retriggering).
Since all 4 will be programmed similarly, you might clean up your block diagram a bit by carrying the task id's through as an array, over which you auto-index a For loop. Also think about whether to pass the error cluster through as an array (individual error chain for each counter) or a shift register (shared for all slave counters).
Regarding "other counter output." This is more restricted than it might sound. You don't get to choose which "other" counter you want. You get what NI has predetermined as each counter's "other." Specifically, they are paired on the 6602 as follows:
(0,1), (2,3), (4,5), (6,7) so that Counter #3 is the "other" counter for Counter #2, vice versa, and likewise for each other pair.

Similar Messages

Triggering a 6024E into data acquisition from start and end number of finite pulse generator from a 6602

My motion control system is driven by a 6602 I wanted to acquire analog current (to a voltage via I/V converter) from a 6024 AI when:
(1) At the start of the pulse generation
(2) Stop at the end of the pulse generation
(3) Read every possible data between and stream it on the harddisk
(4) Option to skip at regular intervals to reduce amount of data accumulation
Anyone have some suggestions? What I did try and attempted was to "loop an AI from a triggered intermediate Analog Input VIs" this is rather erratic!My question for the analog input software are:
(1)Can you trigger an AI to start a continuous acquisition?
(2) How do you do AI from a "start" p
ulse train to "end" pulse train?
(3) How do you manage time for File I/O meanwhile doing (1) and (2) above?
Bernardino Jerez Buenaobra
Senior Test and Systems Development Engineer
Test and Systems Development Group
Integrated Microelectronics Inc.- Philippines
Telephone:+632772-4941-43
Fax/Data: +632772-4944
URL: http://www.imiphil.com/our_location.html
email: [email protected]

"(1)Can you trigger an AI to start a continuous acquisition?
(2) How do you do AI from a "start" pulse train to "end" pulse train?
(3) How do you manage time for File I/O meanwhile doing (1) and (2) above?"
Answer 1 and 2)
Yes you can, This VI is part of the search examples that ships with LV:
"Continuous Acquisition & Graph Using Digital Triggering and External Scan Clock
Demonstrates how to continuously retrieve data from one or more analog input channels using an external scan clock when a digital start trigger occurs."
Go to Search Examples in the Help/Contents of LV. Then pick I/O Interfaces/Data Acquisition (DAQ)/Analog Input/Triggering an Acquisition/Triggering a Continuous Acquistion.
This VI is appropriate ifs you want to clock the DAQ with some clock (external scan clock) other than the on board clock.
The start trigger required by the DAQ card will be a TTL signal attached to the PFI0/TRIG1 pin of you DAQ card (via whatever signal conditioning you have).
The external clock also needs to be TTL and is attached to the PFI7/STARTSCAN pin.
You tell it which AI channel to use and wire that up appropriately.
All of this stuff is in the context help for the VI.
Answer 3)
You have a misconception of how the acquisition makes its way into a file on the hard disk. You don't really "stream to disk." The VI above will run a buffered acquisition. The DAQ card sets up a buffer that fills with the data continously. When you use the VI you set up how the buffer is configured, you will see controls for buffer size, number of scans to read at a time, etc. The acquisition runs data into the buffer continously and reads from the buffer are a parallel process where chuncks of the buffer are extracted serially. You can end up with a scan backlog where the reads are falling behind the data. Making the buffer bigger helps. All of this is limited by the sampling capability of the DAQ card. 200kSamples/second is for one channel of AI. Divide by 2 for 2 channels. etc.
The short answer is that the VI and DAQ card manage the file I/O for you.
The VI above writes the scan out to the waveform chart on the front panel. You will want to wire that data out from the AI Read Sub VI to a spreadsheet file in tab delimited form or similar.
Look inside the VI block diagram. There is a While loop containing the AI Read. Every time the loop runs (unless you hit STOP), the AI Read plucks the specified # of scans from the buffer (starting from the last unread datum). If you wire the double orange wire from AI Read out of the loop (and set the tunnel for Auto Indexing) the Vi will build another buffer in memory that is a series of AI Reads appended to each other, a sequencial record of the acquisition. Here you put in a Write to Spreadsheet VI. This is in the Functions Pallete, it is the first VI in the File I/O Pallette (icon looks like a 3 1/2 disckette).
There is more to it than this. The spreadsheet Write is 1D or 2D only. By running the array out of the while loop with auto indexing enabled, you create a 3D array. (If you turn off auto indexing you will only get the last array performed by the AI Read.) You will need to create a new array withe the pages of the array placed serially into a 2d array. I don't think I want to get into that. It isn't that bad to do, but you should get some time messing with arrays on your own, then you will see how to do it yourself. One solution is to only run the While loop once with a buffer big enough to hold the whole acquisition, or in other words no loop at all. I don't know how many scans you want. The other thing is by wiring that AI Read out of the loop you are creating an array that must be dynamically resized as the loop runs. Kind of a no no. Better to know what you are acquiring size wise and letting the VI set up buffers and array space that does not need to be changed as the program runs.
Caveat: I am fairly new to this and I could be wrong about the arrays and buffers and system resources stuff. However, I have done essentially what you are trying to do succesfully, but not "continuously." I limited the AI Read to one large read that gets what I need.
"Continously" is usually reserved for screen writes as in the VI above. The computer is not required to continually allocate space for an ever expanding array to be written as a file later. Each time this VI runs the While Loop the data goes to the waveforn chart. Each new AI read overwrites the previous one. Sort of like if you turn the Auto Indexing off. When the VI stops, the waveform chart on screen would show the same data as was written to the spreadsheet.
Feel free to email me directly: [email protected]. I will help as I can.
Mike Ross

Pulse Generation application with DAQmx and a PXI-6624 module?

What is the best implementation method for the following pulse generation application
using LabVIEW, DAQmx and a PXI-6624 counter\timer module?
I have two rising edge trigger signals (Trigger-1 and Trigger-2).
There is ample spacing between each trigger. They never occur at the same time.
I need to generate a single pulse (fixed width, variable delay) whenever Trigger-1 occurs and
a finite pulse train (fixed width, variable delay, N-pulses) whenever Trigger-2 occurs.
However, the output must appear on one counter output because this composite signal
will be used as a trigger source for another PXI module in the rack.
With DAQmx and a TIO counter\timer can I use both the GATE (for Trigger-1) and
AUX (for Trigger-2) at the same time on the same counter to gate out the desired pulses?
Trigger-1 would be wired to the GATE of CTR0. One Trigger-1 event would generate one pulse on the output of CTR0.
Trigger-2 would be wired to the GATE of CTR1 and the output of CTR1 would be routed to the AUX input of CTR0.
One Trigger-2 event at the GATE of CTR1 would generate multiple pulses on output of CTR0.
Would DAQmx and the PXI-6624 TIO support this implementation?
What is the best way to accomplish the task at hand.
Thank You.
Best Regards,
Scooby

Hi Scooby,
I have looked into the application you have described and I see a potential problem with what you describe. In DAQmx, it is not possible to call the counters of the same DAQ device in the same task, so you cannot have the finite pulse train generation and the single pulse generation tasks running at the same time. What you can do, since you mention the triggers will not occur at the same time, is to stop one counter task while you are triggering another. The way I would suggest you merge the outputs is with a two input Or logic gate to avoid damaging your counters. Your signals will effectively be added together by this logic gate. I do not see any way to merge the outputs internal to the DAQ device.
Please let me know if I can be of additional assistance.
Laura

Two retriggerable pulse generations after a pulse train generation

I am trying to generate 3 pulse trains (ABCABCABC...) one after another.
The program currently I am using generates 2 pulse trains (ABABAB.....).
I am using the Traditional NI-DAQ and PCI-6602.
I am thinking about using pulse train generation first and then retriggerable pulse generation after that.
I understand that the retriggerable pulse generation can generate a pulse train triggered (or gated) by other counter output.
I have attached a test vi.
It uses the pulse train generation code when the counter number is 0 and when the counter number is not 0, then it uses the retriggerable pulse generation code, which I tried to modify from the pulse train generation code.
First of all, I am not sure if I wrote the retriggerable pulse generation code correctly.
Secondly, I don't know if the whole code will generate ABCABCABC...
I would really appreciate your help.
pchemjjang

pchemjjang,
I believe I may have misunderstood your original concern. It sounds like you want to output this finite pulse train on three different counters. You will output these pulse trains for 10 minutes and cease your program. The Finite Pulse Train.vi will output a pulse train from only one counter. With this Traditional DAQ example you would need to have three of these Finite Pulse Train.vi programs running simultaneously in parallel to output from 3 counters. I would strongly recommend using DAQmx for this application because you will only need to utilize 4 VIs. The rest of the work is done behind the scenes. There is an example in DAQmx which should accomplish exactly what you are looking for in one program. You must make sure to make the number of pulses 2000000, the duty cycle as 1/3 and the frequency as 1/(300us). The DAQmx driver can found here. In terms of the counters, I believe that each task requiring two counters will use the counter adjacent to it. If you would like to output on counter 0 using finite generation then counter 1 will be used as the gating counter. When you have the DAQmx driver then you can find this example by selecting Help>>Find Examples and then expanding Hardware Input and Output>>DAQmx>>Generating Digital Pulses>>Gen Dig Pulse Train-Finite.vi. I have included an image to show how the front panel of this example should be configured to work. The major note to make is that you will need to configure all of the counters in the channel names list. In Traditional DAQ this did not seem possible. In Traditional DAQ you would need to create a subvi out of the Finite Pulse Train.vi run three copies of it, in parallel, in a larger program. Please let me know if you will be able to utilize DAQmx in this application.
Thanks,
Gio L.
Digital Support - Product Manager
National Instruments
Attachments:
Counteroutput.jpg ‏49 KB

Frequency divider/ pulse generation from 1 to n

Hi,
I have a sample pulse which in some cases needs to be divided. I tried to use the pulse train generation function, which works fine (giving me a pulse every n sample pulses), but only starting at 2 input pulses. I need to be able to use this function from a division of 1 and up.
Put in another way, can a counter be configured in such a way that it outputs a pulse every rising edge of the source signal?
I'm using a PXI 6602 counter card and am programming it through calls to NIDAQ32.DLL under Labview 7.

Hi Walter,
In short, no. You can't output a pulse on every input pulse. You can however configure the degree of division. Here are the rules for division:
When set to pulse train generation, you will have a register for the low value of the pulse train and a register for the high value. What happens in typical pulse generation is that these registers are loaded with count values such as 2 and 2 for each register respectively. In default operation, the first register will count 2 pulses on the source and then toggle the output. The second register will then count to pulses and toggle the output again. The operation then cycles back to the first register. This toggling effectively creates a pulse train that is divided by 4 and a duty cycle of 50%.
You can however change the output mode to pulse instead of toggling upon completion of counting on a register. In the above example, you would count 2 source edges and then pulse for the first register and the count 2 more edges and pulse again for the second register. You will of course repeat this in pulse train generation mode. This mode allows you to obtain greater resolution since you are now dividing by 2 but your duty cycle will be different. Each pulsed output will be equivalent in size to the source pulse width.
Finally, the two registers can be populated with integer values of 2 or greater. Therefore, the smallest frequency division is 2.
You will have to work with these three elements to obtain the pulse train of your desired frequency. Hope that helps. Have a good day.
Ron
Applications Engineering
National Instruments

Simple pulse generation toggle

Below is an excerpt from the 6602 manual. The figure may not show so I've attached a word document showing it. I want to do exactly what this says but am not sure how to make it happen. I need to generate a quadrature signal and I think this would work wonderfully. I want to setup one counter as my source and have two others toggle appropriately (keeping 90 degree phase shift).
How do I get into "Toggle" mode???
Thanks!
In toggled mode, the counter output changes state on the SOURCE edge
that follows the assertion of the TC pulse. Figure 3-6 illustrates the two
output modes for a pulse generation with a delay of two and a pulse width
of four.
Figure 3-6. Output Modes
Attachments:
6602 manual excerpt.doc ‏28 KB

Howdy,
You can use any of three DAQmx Create Channel VI's (CO Pulse Freq, Time or Ticks) to accomplish this generation. For this particular application, CO Pulse Ticks would probably be easiest since it allows us to input an initial delay, number of high ticks, and number of low ticks. For example, looking at Figure 3-6, to generate the bottom waveform, we would have something like the following config:
the top waveform (SOURCE) would be connected to the source of ticks input on the DAQmx Create Channel (CO Pulse Ticks).vi
initial delay: 3
high ticks: 4
low ticks: 2
The DAQmx help for DAQmx Create Virtual Channel goes into more detail about these three Create Channel VI's if needed.
(Just in case anyone references this thread in the future, this discussion is referring to Figure 3-6 of the January 1999 version of the 6601/6602 User Manual available here.)
Warm regards,
pBerg

Trigger acquisition and pulse generation

Hi,
I would like to generate a pulse on a PXI 6602 and start aquiring data on a PXI 6133 at the same time.
The attached VI seems to do the job but it has a race condition at the read vi. I am sure there is a better way to implement.
The problem is that the read vi seems to have an implicit wait until done. Labview does not continue but waits until the read vi finishes.
Is there a way to commit a read task to the DAQs and then start and trigger it? Similar to what I did with the clock on the PXI 6602.
Thanks!
Attachments:
DaqAndTimingTest.PNG ‏44 KB
DaqAndTimingTest.vi ‏32 KB

Take a look at this KB article: http://digital.ni.com/public.nsf/allkb/EBD603683446EC13862575B3006A63A2 It discusses how to synchronize your tasks. Not in the examples that there needs to be a start task for each task you create. Also take a look at both the Synchronization Examples in LabVIEW and the Multiple Device Examples. These should illustrate everything you should need to get your system up and running. I would also recommend that you use the Trigger VI's instead of the Property Nodes.
Alex D
Applications Engineer
National Instruments

Start button for DAQ Assistant doing pulse generation

Hi,
I am new to Labview, and I got the USB 6210.
I used the DAQ assistant and selected ctr0 to create a pulse.
This works fine, but the pulse is generated when you run the program.
I want it so that when you press a button, the pulse generation starts. Then when you press the button again, it offs.
How would you do this, I dont see any 'data' input anywhere on the DAQ Assistant. Please help.
Also, I was wondering how to change the digital output line where the pulse will output. Currently it comes out the first D/O line. USB6210 has 4 digital outs, how do I change the output line.
In DAQ assistant, all i see are two choices for pulse, crt0 and crt1 (USB 6210 has 2 counters).
Again I am just learning, thanks for any replies

Hi,
I’m using NIUSB 6218 to acquire measurements from 16 (Ai16-Ai31) displacement sensors and 16 (Ai0-ai15) from ultrasonic sensors. These sensors are activated alternately which means when acquiring data from the ultrasonic sensors the displacement sensors are deactivated. For ultrasonic scan contains 16 channel x 16 samples then it will followed by displacement sensors also 16 channels x 16 samples. The acquisition samples are controlled by the trigger signal (rising edge) from the PIC. The whole system is using external clock from the PIC 20MHz. I’m planning to insert START and STOP button on the front panel. The assignment of the pin is as follows:
          PFI0- Trigger signal (acquiring data) from PIC.
            PFI1- BURST signal from PIC (send all (16x16) acquired data to be displayed/save into spreadsheet file.
            PFI4- START signal to PIC
            PFI5- STOP signal to PIC
So far my VI works when I applied external trigger signal at PFI0. The VI can sample the data but how to inform the PIC that the 16 sample data has been acquired? My problem is I do not know how to combine all these functions (START/STOP/BURST) into my VI. Attached is my sample of the VI which I’m working on. Please advice.
TQ
Attachments:
displacement and ultrasonic data.jpg ‏259 KB

Software triggered single Pulse Generation

Hi,
I have an AT-MIO-16E10 board and I am trying to generate multiple but
finite digital pulses without having to reset, configure and rearm the
counter for every pulse. This takes too much time for my application. I
would like to configure just once the counter and gate it by any
software method. I am using LabWindows/CVI.
Does anybody know if it is possible to rearm the counter without having
to reset and configure it previously?.
Does anybody know how to generate a software trigger?
Thanks
Manolo

Hi Manuel,
Configure your counter for retriggerable pulse generation, and connect
one of the digital lines to the counter gate. Toggle the digital line each
time you want to generate a pulse. See GPCTR_Set_Application(),
application = ND_REGRIG_PULSE_GNR in the NI-DAQ Function Reference
Manual for details. Please feel free to email me if you need more help.
Regards,
Reed.
Reed Blake
Beta Technology
Industrial and Scientific Computing
Manuel Prieto Mateo wrote in message <[email protected]>...
>Hi,
>I have an AT-MIO-16E10 board and I am trying to generate multiple but
>finite digital pulses without having to reset, configure and rearm the
>counter for every pulse. This takes too much time for
my application. I
>would like to configure just once the counter and gate it by any
>software method. I am using LabWindows/CVI.
>Does anybody know if it is possible to rearm the counter without having
>to reset and configure it previously?.
>Does anybody know how to generate a software trigger?
>
>Thanks
>
>Manolo
>

In Delayed Pulse Generation vi,Problem With THE PULSE WIDTH??

In Delayed Pulse Generation vi, I want to input a very low number for the Pulse Width while using an external timebase source. But the minimum pulse width has to be 2. Does anyone know how can I solve this problem??

Hey 45,
Unfortunately, there is no way to generate a pulse width smaller than 2x your external timebase.
There is an option to create a pulse of arbitrary width of your external source if you can afford some software processing in between. What you can do is use 1 counter to measure how many source edges of your card's internal timebase (80 MHz for TIO only, 20MHz or 100kHz for TIO and STC) your external signal is. This uses pulse width measurement as the counter application. Once you know how many source edges it takes to represent your pulse, then you can use triggered pulse generation and use the internal timebase with the pulse specs set to create the exact pulse width you want (and delay) and you can use your external pulse as the trigger. Th
is works well if your pulse is always the same width and you can measure it before hand. As an example, let's say your pulse is 20 internal timebase pulses when measured. This means you can use the pulse specs to specify a pulse width of 0.75 your pulse width by using only 15 internal timebase edges for your pulse width.
I don't know if I was clear above or not but if you give me your exact application you are looking to achieve, I might be able to help you out. Hope that helps.
Ron

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

Can I put multiple object placeholder in Master slide?

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Apple Maps is not a GIS application. It might be one day. For now, you will have to use ArcGIS or something similar.

Monitoring pulse generation

Hi all,
I am using a USB-6210 card and
measurement studio with VStudio2003. I would like to drive a stepper
motor (which turns a miror in a spectrometer) by sending digital pulses
to a motor driver. Using another channel on my card, i would also like
to read a voltage (from an IR detector) every time i send 100 pulses to
the stepper motor on the other channel. The purpose is to be able to
log the voltage against the position of the motor.
I am not sure what the correct method is... I can think of different options :
Use
\National
Instruments\MeasurementStudioVS2003\VCNET\Examples\DAQmx\Counter\Generate
Pulse\GenDigPulse + incrementing a variable that counts each time i
send a single pulse. When the variable reaches 100, i take a reading.
This concept is simplistic, however with this method i am concerned
about having to often start/stop the task.
I have seen interesting examples in the following directories, using a continuous pulse train + counting digital events.
\National Instruments\MeasurementStudioVS2003\VCNET\Examples\DAQmx\Counter\Generate Pulse\GenDigPulseTrain_Continuous
\National Instruments\MeasurementStudioVS2003\VCNET\Examples\DAQmx\Counter\CountDigEvents\
How can i integrate these two examples to be able to count the pulses? Shall I just physically connect the counter pin and the pulse generation pin on the connector block of my card?
To
decide whether the motor has arrived to the aimed position I could use
the a "counting" class to drive (=start/stop) a "pulse generation"
class ?
However the counting methods are driven by a Timing
function (which runs every 50ms max), so i will always end up being
slightly over positionned because of the lag time of the OnTime method?
(i guess it doesnt really matters, as long as i know where i am)
Use
a finite pulse train. This imply using my two counters and then i would
not be able to know where my motor is if the software was to end
prematurely.
Does anyone know what is the right way to do this?
Thanks
Laurent

Duplicate thread:
http://forums.ni.com/ni/board/message?board.id=250&message.id=37363

Pulse generation PCI-6220

Hi there,
I´m an absolutely newbie to labview and hope to get some advices as I´m completely stuck at the moment.
I´d like to generate variable TTL pulses to 3 different lines. Since the PCI6220 card only has two counters I´ve to go for the normal hardware correlated DIO lines.
For now I´d be happy to see it working just for one line as follows:
__| |________| |_ ...
I´ve to be able to set the pulse width of the high time for the first and the second pulse as well as the two different low times. This scheme should furthermore than be repeated n times. Thus having 5 variables, the length of the pulses in ms: 'Low1','High1','Low2','High2', and the number of repetitions: 'n'.
I may be horribly wrong with this, but I think working with the duty cycle doesn´t work for that application, does it?
Assuming I use the frequency generation of a counter as a sample clock to my pulse generation, it seems rather simple taking for instance 'High1' corresponding pulses of the counter clock to generate the 1st pulse then 'Low2' pulses for the subsequent low pulse and so forth. Could anyone give me a hint to do so, or are there better/other ways how to achieve this? Are there eventually vi's available I could start with (haven´t found proper one´s in this forum nor in the Labview implemented library)?
Many, many thanks in advance for any help!!
Robert

Rob: I looked at your example earlier when I was near my LV machine. From memory:
1. I think I recall that you specified PFI 2 as the sample clock source for the digital task while using CTR 0 to generate the clock. According to this doc, the default output pin for CTR 0 is "terminal" 2. However, that does NOT turn out to be another name for PFI 2. Rather, terminal 2 is designated as PFI 12 as can be seen here. (This stuff is also visible in MAX when you select your device, right-click and choose "device pinouts").
2. I recall you used a U32 array version of DAQmx Write. You may need to use the U8 version on your 6220 board. Also, the init values you wrote before the loop alternate between 255 (all bits high) and 0 (all bits low). The values you write inside the loop alterate between 1 (LSB high, all other bits low) and 0 (all bits low).
3. You defined the digital task for finite generation, filled its buffer before the loop, then attempted to keep overwriting it inside the loop. These are not mutually consistent. If you want finite generation, fill once only. If you want continuous generation, it'll take some care not to overwrite too soon.
4. Minor nit: It may not matter in your app, but often its best to start up the digital task before starting the counter task that generates its clock. You can accomplish this by simply routing the error cluster from the digital task's DAQmx Start up to the counter task's Create Virtual Channel.
I'm not near LV now to look at the recent example from Christian M. Hope it suits your needs...
-Kevin P.

How to configure a continuous pulse generation that doesn't end after the VI exits with DAQmx?

Hi,
I'm just learning the DAQmx and I have run into a problem.
With the legacy DAQ API I could configure a counter to create continuous pulses and
when I needed change the freq or duty cycle, I would just call the the configuration function
again. The pulses were generated even after I closed LV, so it was all in the hardware.
Now, with DAQmx api, it seems that this is not possible. I read a forum post saying that
LV will end the pulse generation after the VI exits. Is there a workaround for this?
I could ofcourse create a LV thread for this, but I liked the old one better
It was simpler and I didn't need to worry about threads so much.
All LV operations are going to be inside a DLL that is called from outside of LV, so I can't
use LV threads in a simple way, e.g. putting things inside a while loop. Just that you'll
know why I wan't to avoid using the threads.
Thanks.

It is possible to achieve this behavior using the DAQmx API by using the DAQmx Create Task VI to explicitly create the task (rather than relying on DAQmx Create Channel to do it implicitly) and setting the AutoCleanup attribute to False. This method prevents LabVIEW from automatically clearing the task when your VI (or the function you'll be exporting to your C .dll) finishes executing. The disadvantage is that you might accidentally "leak" a task if you're not careful. In order to stop the pulse generation on command, you can either reset the device or somehow store the task name you created and come back later to call DAQmx Stop and/or Clear Task.
Here's how you would start the generation:
...and how you could come back and stop it later, using the task name you created:
Hopefully this helps-
Message Edited by Tom W [DE] on 11-16-2007 07:54 AM
Tom W
National Instruments
Attachments:
autoCleanup.JPG ‏17 KB
clearTask.JPG ‏4 KB

Multiple pulse generation off master, 6602

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