07-14-2010 08:58 AM
Hello, I am trying to make a program where a user cn telnet into my computer and labview will recevie data and analyze it. it then decrypts the emssage finding which analog output he is trying to change and then change it. I have it all the working but I'm getting the error 50103 which say i cant have 2 DAQ assistant express VIs running simultaneously. I want to have 2 different signals on A0 and A1 on my USB-6281 board. Is this possible? thanks in advance. btw im using labview 8.2
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07-14-2010 09:13 AM
Only one task can be active for a single A/D or D/A converter at a time.
The work-around is to configure the task to acquire from/write too multiple inputs/output and then select which set of data is monitred/written.
So you either have to stop the previous task or revise your code to use more than one output.
Ben
07-14-2010 09:16 AM
is there a way i can have one daq assistant, and when i need to chaneg one of the outputs i can tellt he assistant to change outputs?
07-14-2010 11:53 AM
You have duplicate code in your two cases. Your String to Numeric, the constant 10, the divide, and the Simulate Signal. Pull these out of the case since they will execute no matter what the case is. You can also pull out the Add function and the 0.25 constant and the waveform graph. That leaves the DAQ Assistant inside the case. Get rid of it. Use discrete DAQmx functions. This will be the only way to switch channels in the middle of a program. Inside the case you should just have the channel (AO-0 or AO-1) you want to use. You will have to use DAQmx functions to setup the DAQ with one of the channels, set the timing, trigger, and so forth. After the case, you will have to close the task, then re-initialize (DAQmx Create Channel) using the output of the case structure as the physical channel. This will allow you to change channels. You may have to also set the timing, triggering, etc. Don't forget to close the task when the program ends.
This is why I am against using DAQ Assistant. Its a cheap short cut that does not give you total control. Beginners start using it because it is simple, they get used to it, then when they need versatility they don't know what to do. Learn the real DAQmx functions.
07-14-2010 11:57 AM
@tbob wrote:
...
This is why I am against using DAQ Assistant. Its a cheap short cut that does not give you total control. Beginners start using it because it is simple, they get used to it, then when they need versatility they don't know what to do. Learn the real DAQmx functions.
Amen!
Ben
07-14-2010 12:18 PM
Attached is the vi in LV2009. I have made the mods that I had described. It should be a start. Modify as needed.
07-14-2010 12:45 PM
thats great thanks tbob! i will try and get mroe comfortable wiht the basic functions instea dof using the express VIs. i just started using labview and "graphical programming" so Im still trying to lear the ins and outs. thanks for youre help.
07-14-2010 12:51 PM
could u save it for labview 8.2 compatibilty? i cant open it.
07-14-2010 12:57 PM
I saved it for 8.2 but I got some warnings. You need to check it out thouroughly.
07-14-2010 01:03 PM
awesome thanks il give this a shot