Multifunction DAQ

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Measurement Synchronization


I have the USB based DAQ and a CF card based DAQ device.  My rquirement is to measure power consumed by a iPAQ device. I wanted to know if anyone can suggest me how I can synchronize the measurements. Suppose I want to signal the beginning and end of sampling, how can I get a signal from the iPAQ. I can use the parallel port to generate a trigger signal if it was a laptop. But the iPAQ has limited interfaces.

Is there a way this can be done? Any suggestions are welcome.

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Message 1 of 6

I am a little unclear as to what you mean by the phrase "signal the beginning and end of sampling".  Do you mean that you want a signal from the IPAQ to trigger the sampling?  Also, what measurements are you trying to "synchronize"?  This will really hinge on what USB DAQ device you are referring to.  There are E-series DAQ Pads, USB-6008/9, etc...  Each of these has different triggering capabilities.  Can you clarify your objective a little more?

Jeffrey Phillips
National Instruments Applications Engineer

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I am using the CF 6004 and USB 6008 DAQs. I know that these have digital inputs that can be used to signal the start of the sampling and stop the sampling also. What I was interested in finding out is that, is there some way I can generate this signal from a handheld device?

Since the handheld device has only a USB and serial ports and since I am using the serial port for connecting it to my Laptop, is there a way to do this? Also, I wanted to be able to do the generation of the signal from Linux installed on the handheld.


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I'm still a little unclear as to the physical set-up.  See if this is correct:
You have an IPAQ with Linux embedded on the PDA.
This IPAQ is connected through serial to the laptop.
The laptop is connected via USB to the USB-6009.
You want to generate a signal from Linux on the PDA to trigger the program in LabVIEW on the laptop via the USB-6009.  Is that correct?
The CF6004 cannot be accessed from Linux embedded on the PDA.  Furthermore, the serial digital logic levels are not compatible with the logic levels on the USB-6008.  In short, this is probably not going to work.  However, you might want to look into sending a message from the IPAQ to the laptop. 
-Jeff P.
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Message 4 of 6
Sorry for not being clear the second time also.

The setup is like this (as you mention)

The iPAQ (running Linux OS) is wired to measure power. The wires are connected to the USB 6008 device (analog inputs). The USB 6008 device is connected to the USB port of the laptop (running Windows XP, NI DAQ software) and is logging the results. For now, I am triggering the samples by clicking "Start" in the Measurements and Instrumentation software on a certain task I have setup.

In addition to this, the serial line output of the iPAQ is connected to the laptop serial port and I use hyperterminal to access the iPAQ.

Now, there is something running on the iPAQ for which I need to make power measurements.

Since I have a lot of software to run in the iPAQ, I wanted to create an automated measurement setup so that when something is run on the iPAQ (I add aditional code on the iPAQ) it also triggers the 6008 to start sampling. I was thinking something of the nature of sending a signal on the USB port. But, I am not sure if this is possible or not. If you can give me some pointers on what other people might have done or what can solve this porblem for me, it would be great.

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Message 5 of 6
If I understand literallyl what you are saying, then I have to say "no".  You cannot hardware trigger the acquisition with a "signal" sent from the IPAQ to the USB 6008.  However, if by "trigger", you mean to start and stop the data acquisition through the USB 6008, then you can have the IPAQ send a "command" through the serial port to the computer to logically tell the computer when to start the data acquisition.  By "Measurement and Instrumentation Software", are you referring to LabVIEW or to the Measurement and Automation Explorer (MAX) that installs with the DAQ driver.  If you are using MAX to start and stop your task, then this computer-received "command" from the IPAQ will not work.  MAX was not designed to do data acquisition, just verifying hardware functionality and configuration.  There is a functionality in MAX called VI Logger Lite that was designed and can be used to do data acqusition, but cannot be programmatically started and stopped.  It runs exclusively off of timed acqusitions.  However, If you are referring to LabVIEW by "Measurement and Instrumentation Software", then this is possible.  Use the IPAQ to send a software command through serial.  Have LabVIEW read the serial port and logically interpret the command and software trigger the data acquisition.
Hope this is hepful.  Sorry  it took so long to understand the physicaly set-up.
-Jeff P.
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