Two DAQ tasks in a certain sequnce

Hi everyone
my mission includes two DAQ task, one is AI (voltage input), the other is DO(counter PWM output). the problem lie in the somewhat time sequence. that is,
in a word, the recording (AI) is a little longer than generating (DO).
for clear description, there are three episodes,
1. recording began and last 50ms, at 1000Hz rate,
2.the PWM generation began after recording began 50ms, the PWM frequency and duration could be set by a controler, meanwhile, the recording go on
3.when the PWM output ends, the recording keep last 100ms, then recording completes.
the point is that the recording couldn't be disrupted by the PWM in the whole mission.
How could I arrange the two task ?
my card is a M series one.
THANK YOU advanced

Yamaeda 已写：
- Setup the two tasks
- Start AI task and Read 1D array of 50 values (samples)
- Start DO task.
- Poll Task complete in a 0ms wait loop
- wait 100ms
- Read AI task 1D array with -1 samples (grab all)
/Y
Thank you very much! Yamaeda.
I am freshman. May I ask more clearly?
1.Do you mean that it doesn't obey syntax? when a task line include more than one "DAQmx read.VI", and as a matter of affect, the recording isn't interrupted between two DAQmx raed.VI?
2.How to merge the the two"read.VI" output in one awaveform chart rather display them separately in two chart?
3.How to insert a wait in the DAQmx task? use a sequence structure with a "programing/time/wait" or a "time delay express VI"?
thank you again!

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How can I combine these two DAQ tasks???

I am using LabVIEW 11, Windows XP, cDAQ-9174 chassis, two NI-9205 modules.
Please see my code for reference. I am very new so i will accept all suggestions.
I am acquiring 12 volatage signals in a producer/consumer structure giving me a queue of 1-d array of waveform(dbl). Then I am acquiring 12 voltage signals in another loop giving me 2-d array of waveform(dbl).
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Attachments:
WaveTest_6.2.vi ‏558 KB

Hello chrisbe723,
When you say that there is an issue creating the channels, are you getting a specific error message when running your code? Also are you referencing the same set of channels for the two DAQ task you are configuring?
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How many DAQ tasks per loop?

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I am working on a system in which I have to read signals of 5 different sensors which have different ways to communicate (4 - 20 mA, voltage, RS-232, ModBUS, etc.) with the DAQ Device (cDAQ in my case), at same time when I am reading the variables I must check for the state of several digital inputs to verify connections and if any is interrupt I must stop the Data Acquisition.
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Message Edited by John P on 03-25-2010 06:35 PM
Message Edited by John P on 03-25-2010 06:36 PM
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DAQmxAO Write DC& Raster switch.vi ‏280 KB

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Solved!
Go to Solution.

Never mind...
Found it as "DAQmx Save Task"

Is it possible for a DAQ task to just stop responding to commands?

The software I am working on controls a NI USB-6501 digital I/O device using the NI-DAQmx library. When the software initializes, it attempts to create 10 "tasks" (for different I/O lines of the device) using DAQmxCreateTask(). If any of the tasks cannot be created, the software should close with an error message.
if ((!CreateTestModeTask(&TestModeTask, USBdevname)) &&
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     (!CreateChargeEnableTask(&ChargeEnableTask, USBdevname)) &&
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Once the tasks are created, the software goes on to use them to manipulate the I/O signals of the NI USB-6501 device with DAQmxWriteDigitalLines() or DAQmxWriteDigitalU8(). The software does not check whether these functions return an indication of success or not... The assumption is that it works every time.
This is my question:
At run time, is it possible for a successfully created DAQ task to simply stop responding to commands? This is what I believe happened. I observed it only once out of hundreds of trials, but it is still a great concern. Only 1 task stopped properly controlling the NI USB-6501. All of the other ones continued to work properly. It continued to misbehave until I closed and re-started the software (thus re-creating all tasks).
And if it is possible for a task to simply stop responding, is there any way to prevent it?
-Mike

Your assumption that instructions will work every time without facing errors is excessive in my opinion. I never observed a daqmx task simply stopping responding to commands: every time it happened, an error condition was raised explaining the misbehaviour.
I would add some error checking where you are manipulating the daq board and look into the informations the error message gives you.
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Two DAQ tasks in a certain sequnce

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