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Update digital output at kHz

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#1 Elliott

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Posted 27 August 2012 - 10:19 AM

Hi, I am trying to use a UE9 to test another data acquisition system that has a digital input. I want to output the DB37 or DB15 ports to the digital input of the DAQ that I'm developing, then output known values with the UE9 and ensure that they are all received correctly. It is critical that I can change the digital outputs of the UE9 at a high rate. For this to be a useful test I need to do it at at least a kHz, 20 would be preferable. I have gone through the LabJack documentation and examples (very useful by the way) and have seen some useful features but none that really does what I need. In the LabJack API, it seems like what I want is the "stream-DAC", but for the digital outputs. Does this exist and I'm missing it? I have also looked at using timers, but I don't see a way that I can change the digital outputs at known intervals. I'm currently using a Windows 7 machine and the LabJackPython sources, but I have OSX and Linux machines around and am comfortable with Matlab and C. Good job with all the online information. I apologize in advance if I'm just missing something. Elliott

#2 LabJack Support

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Posted 27 August 2012 - 02:04 PM

From Section 3.1 of the UE9 User's Guide we see command/response times of 1.7 or 1.5 ms, so you can get close to 1 kHz but likely not quite there. Stream-DAC only supports analog outputs on the UE9. On the upcoming T7 you will be able to do digital also. Also, the T7 will eventually have scripting support so you could program it to do what you want in hardware. Timer outputs are just square or rectangular waveforms. The one other thing you might look at is the SPI or Asynchronous functionality. You can use these to get digital information out on one channel quickly.

#3 Elliott

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Posted 28 August 2012 - 08:19 AM

Thanks for the response. I'll follow up on those couple of ideas. I'll update this if I get something to work out. Thanks again, Elliott

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