Two counter outputs with 90deg phaseshift

Hi,
I have NI PXI-1042 chassis and two NI PXI-6513 digital output cards in it.
Task is to create two pulses with 90degrees phaseshift.
Is there function in labview 7.1 which generates pulses descriped above. I`m meaning that if I tell function to count up, signal A is ahead signal B and if A is 90 degrees behind B it means counting down?
Is there way to do this by connecting 3 (signal A, signal B and GND) counter wires all in one counter and controlling only one counter to "count output down" or "Count output up"?
- Santtu

Hi Santtu,
I think I understand what you are trying to do.
Essentially you have two counters, but you want to be able to control their
phase relationship to one another. This is definitely possible to do;
however, there are not many examples dealing with it.
I did find one Traditional DAQ Example (non- M-Series) that
might help you out with this: Twin
Pulse Train Generation with Variable Phase Shift Control
Traditional DAQ uses an older API, so I would recommend you look at the
attached example over this example. Just wanted to give you more
than one option.
As far as it 'counting' up or down, that really would have
to be done by a counter input task. Since the input would be the same as
that for a quadrature encoder, then you would use the methods described in my
previous post. As the output it will simply look like two different
counters.
For the best solution though, I went ahead and created an
example for you. It shows how to generate 2 different counter pulses that
are out of phase with one another by a specified amount of time.
Hope this helps,
Otis
Training and Certification
Product Support Engineer
National Instruments
Attachments:
Gen Dig Pulse Train-Continuous-Dig Start-Phase Shift.vi ‏82 KB

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Synchronize two counter outputs on 6071E card

Well, it's the usual how do I synchronize two counters problem.
I'm using the 6071E with DAQmx .NET 4.0. I define a Task and attach to it two counter output channels with implicit timing and zero initial delay . When running the program
I catch the first edge with a scope single trigger. There is always a delay between the first edge of ctr0 and the first edge of ctr1 of 16.3 microsecs. Is there a way, besides setting the initial delay of ctr0 to 16.3 microsecs, to make the counters to always start together? what is the source of the delay(software/hardware) and should it always stay constant.
any help is welcome
Solved!
Go to Solution.

The source of the delay is that despite being in the same tasks the counters are still started sequentially by software. I'm surprised the delay you are seeing is constant.
If you want the counters to start together you should configure a start trigger. Once you start the counter tasks in software, issue the start trigger to begin generating your output pulses. The start trigger must be a hardware signal--as an example you might configure a software-timed digital output and wire it back in to one of the PFI lines.
If you want to avoid any additional wiring, you could split the counters into two separate tasks. Trigger one counter with the internal output of the other (start the task that is going to be triggered first). Doing this instead of using an external trigger, I would expect an additional delay between the counters on the order of 100 ns as the initial delay is at minimum 2 timebase ticks.
Best Regards,
John Passiak

How to synchronize two analog output with USB-6353 sharing a trigger

I'm have the need to synchronize two analog output on the same device (USB 6353) sharing a trigger signal on PFI0.
The programming environement is Visual C++ , and the code I wrote is as following:
DAQmxCreateTask ("", &Ao0TaskHandle); // is the task handle for the analog output Ao0
DAQmxCreateVoltageChan((Ao0taskHandle,"Dev1/Ao0","",-5.0,5.0,DAQmx_Val_Volts,NULL);
DAQmxCfgSampClkTiming(Ao0taskHandle,5000.0,DAQmx_Val_Rising,DAQmx_Val_ContSamps,1000);
DAQmxCfgDigEdgeStartTrig(Ao0taskHandle,"/Dev1/PFI0",DAQmx_Val_Rising);
DAQmxCreateTask ("", &Ao1TaskHandle); // is the task handle for the analog output Ao1
DAQmxCreateVoltageChan((Ao1taskHandle,"Dev1/Ao1","",-5.0,5.0,DAQmx_Val_Volts,NULL);
DAQmxCfgSampClkTiming(Ao1taskHandle,5000.0,DAQmx_Val_Rising,DAQmx_Val_ContSamps,1000);
DAQmxCfgDigEdgeStartTrig(Ao1taskHandle,"/Dev1/PFI0",DAQmx_Val_Rising);
DAQmxWriteAnalgF64(Ao0taskHandle,1000,FALSE,10.0,DAQmx_Val_GroupByChannel,AOdata,NULL,NULL); AOdata is a buffer containing a sinwave
DAQmxWriteAnalgF64(Ao1taskHandle,1000,FALSE,10.0,DAQmx_Val_GroupByChannel,AOdata,NULL,NULL);
DAQmxStartTask(Ao0taskHandle);
DAQmxStartTask(Ao1taskHandle);
What happen as result of the code is that only the Ao0 channel get the sinwave output , but not the Ao1 . It seems the two channels are not synchronized.
What is wrong in my code?
Please any help non referred to a LabView soloution , first because I'm not a LavView programmder and secondly the project impose C++ as the unique environement.
Thanks
Enky

It will depend on what you are programming the NI 5112 device with.
If you are using LabVIEW, you can use the example program attached below. In it, it will show you how this is done.
If you are using VB, VC++ or CVI, you can look at one of the NI 5112 shipping examples that are installed on your computer. These are located in the VXIPNP folder. For example, the VC++ example would be located here:
C:\VXIpnp\WinNT\NISCOPE\Examples\c\MStudioC++\5112Sync
These examples will show you how to synchronize the two digitizers.
Let me know if you have any questions about these examples.
Brian
Attachments:
Multiple_NI_PXI-5112_Synchronization_Demo.llb ‏151 KB

I get two different outputs with "Digital 1D U8 1Chan NSamp"

I have two variations of a program that I am using to try and synchronize data collection at different rates.
Version A:
I have an anemometer attached to the DAQmx Create Channel (DI).vi
The Create Channel VI enters a while loop, and connects to DAQmx (Digital 1D U8 1Chan NSamp).vi, collecting 2000 samples
This create an output that feeds into a Build Waveform
The output of the waveform goes into NI_MAPro.lvlib:Extract Single Tone Information.vi to determine the dominant freqency of the pulses from the anemometer
The frequency gets multiplied through by a constant to determine the reading off the anemometer.
When I run this version of the program, I get that the windspeed is approximately 4-4.5 mph
However, I then needed to coordinate this 2-second collection rate with a photogate that is measuring rpm of a gear (60 teeth, approximately 20rpm, so pulses on about a 50ms cycle). I then created version B of my program
Version B:
Utilizes two While loops.
While loop #1: Just as in version A, but the reading off the anemometer at the end gets fed into a global variable (which is initialized to zero at the very start)
While loop #2: Uses a series of nested Case Structures to determine if the photogate has detected a new pulse, and if so, updates all outputs derived from the photogate data to determine what tooth we're on, the rpm, the time since the program started, and pulls the current value of the global variable.
Both While loops are slaved to a Wait Until Next ms Multiple delay of 1ms to try and synchronize the two loops.
Now, when I run this program, in the exact same conditions, I get a windspeed of about 8-9mph, and the values from the global variable update about every 4 seconds (which seems to imply that there's a related problem).
Can anyone help with this?
-G-

I'm sifting through the results for Time DIO (thanks for the quick suggestion). In the meantime, here are the two versions of the program. From what I've seen distant professional colleagues do, it should be fairly straightforward
Attachments:
Simple - Wind.vi ‏32 KB
RPM, Angle.vi ‏60 KB

Counter Input with Delayed counter Output with board 6023E

HELLO
Is possible with board 6023e have two counters working at same time in this case i need a counter to creat a delay and another one to read. If isn´t possible how i can have a delay in microseconds.

Yes, each one of those boards have two STC counters you can use. Take a look at the User Manual of the boards for more information. When looking at the pin diagram for the boards, the counter pins are GPCTRx_.
If you are using LabVIEW, CVI, VB or VC++, when you install NI-DAQ, it will install a lot of counter example programs which will show you how to program the counters.
Brian

Different Counter Outputs with different number of samples

I´m using an 6602 Timing I/O Board and/or a MIO 6281. For timing control of our measurements I use different counters from both boards triggered by a Digital Out for synchronization. The counters are set to CO Pulse Time, implicit timing, digital triggered and finite sample mode.
Lets assume I use two Ctr´s from the 6602 board. My problem is when setting the number of samples from only one CTR to another value then the second I´m getting an error. The rest works perfect, I can use different starting delays, low or high times, only different sample amounts don´t work. It´s regardless if I use the Timing I/O or Multi I/O board.
For example:
Ctr 0 / 6602 _ _ | |_ _| |_ _ --> 2 samples
Ctr 1 / 6602 _ _ | |_ _
Somebody any idea or advice?
Solved!
Go to Solution.

Here is my currently used code, perhalps it helps you understanding the problem. Both are doing the same but one is a bit optimized. Hopefully someone can help.
Attachments:
Example_1.png ‏70 KB
Example_2.png ‏90 KB

Counter Output with NI cDAQ 9188

I am trying to generate pulses with the counters included in the NI 9188 cDAQ chassis.
I tried first to do that with NI 9411 module but this task didn't figure out in MAX.
I'm trying now to perform that with the PFI 0 BNC connexion in the chassis but that still doesn't exist in max
what should I do?

Duplicate Post
Best Regards,
John Passiak

DAQmx: 2 Counter Outputs in 1 Task?

Is it possible to have two counter outputs with different timings in one task?
One counter will be used to generate a PWM pulse train and the other one will be used to re-arm the trigger for analog data acquisition.
Thanks for your help.

Hi,
Thank you for posting to the NI forums. You should be able to output on two counters with separate timing sources. I’ve done just this using an M Series DAQ device and the DAQ Assistant’s auto-generated LabVIEW code. The screenshot to this VI is attached below.
I hope this helps. Please post back if you have further questions.
Ed W.
Applications Engineer
National Instruments
Message Edited by Ed W on 01-26-2007 01:50 PM
Message Edited by Ed W on 01-26-2007 01:50 PM
Message Edited by Ed W on 01-26-2007 01:51 PM
Attachments:
Two Counters.JPG ‏56 KB

Can I generate pulse trains on more than one counter output at the same time?

I have a PCI 6601 card with a BNC 2121 to connect the signals to two devices. The card is used as a trigger for both devices and I want to be able to generate pulse trains on two output channels at the same time, with a time delay between the two. How do I do that in Labview 7.1 Development with DAQmx?

I feel foolish for not being able to figure this out, but it still doesn't work. Attached is the VI I use now. Counter 0 generates a finite pulse train and I programmed Counter 1 to generate a retriggerable single pulse triggered by CtrOinternaloutput. I still get the same error message: -50103 The specified resource is reserved. The operation could not be completed as specified.
The same happens if I set the trigger for counter 1 at PFI36 (default output of counter 0) or any other PFI line. If I try a pulse train generation on only one of the counters, both work fine.
If I try the example in traditional DAQ for multiple counter outputs with phase delay, it works fine.
Can you tell me what I'm doing wrong?
Attachments:
Shutter_AND_lamp_trigger.vi ‏103 KB

Buffered counter output in C

Hi everyone,
I am looking for a possibility to generate a finite buffered counter output with varying pulse widths, using the X-Series. I am working in C / Python.
I want to output two pulses triggered to an external signal. The first pulse should be short, the second pulse long.
The following code outputs only two identical pulses. How can I modify it to output two different pulses?
CreateCOPulseChanTicks(channel,"","100MhzTimebase",DAQmx_Val_Low,0,300,300)
CfgImplicitTiming(DAQmx_Val_FiniteSamps,2) #output two pulses
CfgDigEdgeStartTrig(src,DAQmx_Val_Falling) #external signal
SetStartTrigRetriggerable(True) #retrigger
Best Regards,
Stefan

It's good you found a workaround but the behavior doesn't seem right to me...
The default behavior in DAQmx (the C / LabVIEW / .NET APIs) is to regenerate data from the buffer. Perhaps the python wrapper you are using is disallowing regeneration somewhere? I tried this with regeneration disabled and it gives the same behavior you reported (though with regeneration enabled it does not).
You can use DAQmxGetWriteRegenMode to verify this theory and DAQmxSetWriteRegenMode to enable regeneration in case it is disabled.
Best Regards,
John Passiak

How to Immediately Change Counter Output Rate?

I have a piece of code that largely works like this example: http://zone.ni.com/devzone/cda/epd/p/id/5493
In other words, I set up the Counter Output with some initial frequency and duty cycle, but then during the main loop of my program I continuously change the frequency to a new value based on other criteria.
I'm using an M-series PXI card and LabVIEW RT.
The problem I'm having is that the card waits for the next edge before changing the counter output rate. For instance, lets say it is going at a low frequency and I am upping to a high frequency. If the command arrives in the middle of the current pulse, it will wait to complete the low-rate pulse before starting the high frequency output. Is there a way to make it interrupt the current count and immediately start counting at the new rate?
Thanks,
Isaac

Hi Isaac,
I posted the code in LV 8.2 so you should be able to open it now (it sometimes takes several minutes to upload).
There are a few limitations to using the digital lines instead of the counters:
1. The digital lines are updated off of a sample clock which will be much slower than a timebase. For example, on the 6221 the maximum update rate is 1 MHz, while the counter output has a max timebase of 80 MHz. As a result, the number of frequencies you can generate are going to be more restricted (divide down from 1 MHz vs. 80 MHz).
2. On M series devices, the digital lines must be clocked from an external source. This could be generated from a counter
3. You have to build the digital waveform, which is a bit tricky (I think the example code should help out with that but I haven't had time to thoroughly test it).
4. If you are generating digital lines at fast rates, you will need to write quite a few samples at a time to the output buffer to ensure the data does not underflow. If the buffer includes multiple periods of the digital signal, you would have the case that using the counter output would still update more immediately.
Again, to determine the best course of action it would be useful to know what frequencies you want to generate and which exact hardware you are using. I just mentioned the digital lines as an alternative to the counters, but it might not be ideal for your situation.
-John
John Passiak

How to use counter output pulses to trigger analog input?

Hello all,
I hope the kind people using this forum can help me, a lowly beginner LV programmer! I have been attempting to create a VI that produces a user defined number of TTL pulses, separated by every n seconds. Each TTL would be outputted to a stimulator, which in turn generates its own TTL. Using the stimulator-generated TTL, I would like to trigger finite analog data acquisition (e.g. for every TTL, trigger the collection of a data sweep that contains 4000 samples (collected at 4000 Hz), with 1000 samples collected pre-trigger. I would like to also be able to see each data sweep as it is triggered on a chart. As I understand things (lots of online/book/forum reading), I should be using the counter output to generate my TTL pulses, and syncing each counter produced TTL with analog input, as well as using a reference trigger. Also, the AI part should be started first, so that I don' t miss any counter outputs. If it matters, I also need to use one of the AI channels to acquire the TTL, so I can see my stimulator-induced responses to the stimulator in time.
I am able to generate the TTL pulses from the counter output, but I am having a problem with the AI part. I am unsure how to sync the counter output with AI. Also, since I need to acquire pre-trigger samples, I would be needing to acquire samples continuously, but when I set 'continuous samples' on daqmx timing, the VI doesn't work (hence why's its set to 'finite samples').
I hope someone out there can help, as I have been at this for what seems ages, with limited success. I am using a USB-6259 and LabView v8.2. Thanks!
Attachments:
RC001 v_1.vi ‏49 KB

Hello,
Due to the fact that analog tasks themselves are not retriggerable, a
pulse train produced by a counter is always used as the sample clock
for the analog input task in order to recreate a retriggerable effect
for analog input. This can be done by creating a finite pulse train set
to retriggerable using the DAQmx Trigger Property Node, or the pulse
train could be continuous and just be gated by another signal. Neither
of these methods can be properly applied in hardware to create a
retriggerable reference trigger. You can however implement something
similar in software by just stopping and restarting your reference
triggered analog input task within a loop. There will be some delay
between when the task is stopped and restarted, as these events require
software intervention, but if there is enough time between when each
trigger signal is generated, there should not be any noticeable delay
or missed samples.
I have attached an example of this!
Mark B
===If this fixes your problem, mark as solution!===
Attachments:
RC001 v_1mod.vi ‏25 KB

Two Counter channels in one task ID with DAQmx?

I am writing a program which will control the movement of a gimble on the X and Y axis with servo motors while recieving
position feed back from two encoders on those axis. I am using a 6251M series card's AO to control the movement
of the gimble, while running the encoders into a 6602 for position. When setting up my task ID in MAX I noticed I could add
both ctr0 and ctr1 to the task ID, but when I tried read the counters with that task I got an error in Labview and with the
test function in MAX saying I need to use a multichannel read. I can not find a multichannel read under the counter
section of my DAQmx read, and was wondering if this is even possible. I am used to programming with Traditional DAQ
and know you have to keep separate counter task ID's, but having bought an M series card and having to use DAQmx I
was wanting to know if I could combine them.
Thanks

You can have multiple channels in a single task, but those channels all
have to be of the same type. You can have analog inputs together
with other analog inputs, but cannot combine digital inputs/outputs,
analog outputs or counter tasks with that analog input task.
Once you pair only like tasks together then you shouldn't run into any more issues like this.
Best of luck,
Otis
Training and Certification
Product Support Engineer
National Instruments

How can I wire two PWM outputs of Accelerometer into PCI-MIO-16E boad with SC-2043-SG?

I have been using counter/timer pin since the accelerometer (ADXL202AE, Analog Device) provides about 550Hz PWM signal. The purpose of the project is:
- To acquire PWM signals with Full cycle(ms) and Posity duty cycle(ms) generated in Accelerometer.
- To convert the cycles into acceleration value.
By using counte/timer(GPCTR0_Source) and Trigger(Trig1) on SC-2043-SG board, the signal was obtained.
However, after converting the PWM signal to acceleration value and plotting with labview on-line, the sampling rate was pretty low (26-28samples/sec).
Then, I began to doubt that there is a wrong wire connection. Even though I am using one counter/timer pin, the sampling rate
was low. The purpose of using the acceleration was to obtain two output using two counter/timer pins.
Could anyone help me wire pins and solve the problem?
GINO.

Gino,
You should definitely be getting many more values in your buffer. You should actually be getting 500,000 values every second because a measurement is being taken for every pulse. I found a couple knowledgebases that describe error -10920 and how to remedy it. One is pasted below and the other can be found through the link.
But I'm not sure if you're going to be able to fix this problem because you're measuring pulses at a very high rate. What is happening is every time a pulse width measurement is taken it is put into an onboard (DAQ board) FIFO buffer that is 9 samples long. The computer then reads these samples out of the FIFO and into an a buffer that you can see in LabVIEW. I think the FIFO is filling up too fast and the computer is not able to read the data out fast enough. Therefore you are losing samples because they are being overwritten. This is all dependent on your system.
Here are some benchmarks for pulse measurements:
The following numbers were derived from a Gateway with 128 MB-RAM and an Athlon 700 for ONE counter of the PCI-6602. The number of counters you are using will affect these numbers.
Finite Buffer
Buff Period - 7.25 MHz
Buff Pulse Width - 7.25 MHz
Buff Semi-Period - 3.35 MHz
Continuous Buffer
Buff Period - 250 kHz
Buff Pulse Width - 250 kHz
Buff Semi-Period - 140 kHz
You should still be getting many more samples than 26 though. Try using this example with a very slow frequency pulse to make sure it operates correctly. Then start speeding up the pulse and determine when you get error -10920.
Here is an internal knowledgebase that may help you:
Title:
After Long Periods of Acquisition with AI and Counters, a -10920 Error Occurs
Problem:
A customer has a PCI-MIO-16E-4 and his application is acquiring analog input signals and performing event counting with the buffered event counting mode. The problem is that the buffered event counting is at some arbitrary amount of time (e.g., after 2 days) getting an error with the number -10920. The questions are:
1. Why is he getting this error?
2. Do you know how big the FIFO is for this buffered event counting?
3. When he shares a DMA channel with the floppy controller, how can we make sure they use separate DMA channels?
Solution :
Here are the answers to the above questions:
1. There is probably just some noise on the signal line coming in at some point. The STC is VERY sensitive, so if there is any fast glitching, it will attempt to transfer all of these. This can also happen if the signal does not ramp up fast enough, resulting in double-triggering in the middle region. Use a filter, or a Schmidt trigger*, to clean up the signals. Another suggestion is to use the PCI-6602 with filtering.
2. There is no FIFO used for the counters. The mMite has its own FIFO, but it is only about 9 samples long.
3. PCI does not "share" DMA channels. It may technically be the same DMA channel number, but this is just for reference. PCI cards use Bus Mastering. With Bus Mastering, the operating system gives up control of the PCI bus so that the hardware (in this case, our DAQ board) can handle its own data streaming, eliminating the extra step of having the OS monitor the transfers. The DMA channel numbers are just the "channels" that are supported by the mMite chip. You can have 3 PCI cards in the PC, each with DMA 1, 2, 3, and none of them will actually be sharing any resources.
And another knowledgebase about error -10920
http://digital.ni.com/public.nsf/websearch/8FB9091CB9BB452B8525642000554799?OpenDocument
Hopefully this all helps,
Erick D.
NI Applications Engineer

Hardware-timed counting of two TTL sources with a pair of PCI-6014's

First, in a nutshell: I'm trying to count TTL pulses from two photon
detectors with short (.1-1 ms) integration times, for fluorescence
correlation spectroscopy. I have a pair of PCI-6014 DAQs, each with a
BNC breakout box.
First I created a LabView vi in which the counter from Dev1 outputs a
pulsetrain of the appropriate integration time, and then Dev1/CTR0 out
is physically routed to Dev2/PFI0 to time the acquisition of TTL pulses
on Dev2/CTR0. This seemed to work fine. The vi is attached below
(1_counter_works).
Then I added a second counter task, using Dev2/CTR1. Up until now
I've
been using a LabView vi in which I use this same idea, but with a
software-timed loop for integration times of >5ms. Software
timing
is too slow for shorter integration times, which is why I'm trying to
use hardware timing. But when I add the second channel, I
get the error "No DMA channels available", which is reasonable, I
guess, because each pci6014 only has one DMA channel. So then I
tried to measure and queue the data in one loop structure, then pass it
to a second loop structure to analyze and display the output (and
eventually I will also update a large data array). But I still
get the same DMA error. That vi is also attached below
(2_counters_queue_notworking). Perhaps I'm not doing the queueing
correctly. I also tried doing the counter measurement and
queueing sequentially in a flat sequence, but was unsuccessful.
This question seems to have come up several times recently, but not
with the exact hardware I have. I've looked through
this thread,
this one, and this one,
and haven't been able to solve the problem on my own.
Can anyone tell me if this is going to be possible with the hardware I have, and if so, how to go about employing queueing to
Attachments:
1_counter_works.vi ‏96 KB
2_counters_queue_notworking.vi ‏134 KB

Problem solved by adding a DAQmx channel properties step, specifying
the data transfer mechanism as 'Interrupts' instead of 'DMA'.

Two counter outputs with 90deg phaseshift

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