T7 Analog Channel Streaming

[IntelSen]

I am working on a demo program that will have two analog inputs (AIN0 & AIN1) on a T7 my initial objective would be to stream in the data. The current program is graphing the individual channels on one page and averaging (boxcar) the two channels on another page, thus far everything works well. I will soon need to stream the data in and I cannot find any examples for data streaming for the T7? Please excuse me if I missed the T7 stream example. 

[AzeoTech]

The T7 is an evolving product (though very quickly reaching maturity) and so the examples are limited.  Streaming is also a little more crude than streaming on the UD devices (U3, UE9, etc).  In the UD streaming, data is automatically streamed into channels. In the LJM (T7) version, you have to script reading the streaming data and putting it into channels.  This also means you can get the data and do something else with it if you want.  I expect we'll add streaming direct to channels at some point soon.  In the meantime, I've attached a sample.

 

The StartStream sequence is where all the work is.  Line 3 actually starts the streaming, then the rest of the sequence takes care of continuously reading the stream data and putting it into our AIN0 channel (which could be named something else of course).  StopStream simply stops the startStream sequence and sends the command to the T7 to stop streaming.

 

 

[Ian]

I'm so new here I don't see where to download samples.

[AzeoTech]

No, its me.  I always forget that in this forum after selecting the file, you have to click "Attach this file" to actually upload it to the post.  Hopefully its attached to this post instead...

ljmStreamTest.ctl

[IntelSen]

Downloaded the sample program I added two buttons one to start stream and one to stop stream. When I click on the start stream I get "C1000 Channel or function not found: startStream Line 13 - Uncaught error in sequence startStream". Also I attempted to add a variable value component to display the channel value, for the expression I tried to use the expression ain0, seems as though there is an error trying to use this as an expression?

[AzeoTech]

There's nothing wrong with the expression, you just don't have data in your AIN0 channel yet because of the error in the startStream sequence.  As to the error, I am unsure.  The script works perfectly for me.  Can you post your version of the script?

[IntelSen]

private scansPerRead = 500
private scanRate = 10000
device.labjackM.LJM_eStreamStart("ANY", "AIN0", scanRate, scansPerRead, 1)
private dataIn
private data
private st = systime()
private s
global backlog
global dt
private s = 0
while(1)
   dataIn = device.labjackM.LJM_eStreamRead("ANY")
   data = insertTime(dataIn.data.AIN0, st, 1 / scanRate)
   st += scansPerRead / scanRate
   ain0.AddValue(data)
   backlog = dataIn.ljmscanBacklog
//   delay(0.1)
//   ? "" + data.deviceScanBacklog + " : " + data.LJMScanBacklog + " : " + data.data.ain0
endwhile
 

[AzeoTech]

Update: worked directly with IntelSen.  The issue was old firmware and kipling on the T7.  Lesson of the day: if hardware doesn't work the way you think it should, especially LabJack hardware (because they are constantly adding new cool stuff), make sure you have the latest firmware and drivers from the manufacturer.

[Ian]

Running the sample unchanged I get:

C1000 Channel or function not found: startStream Line 13 - Uncaught error in sequence startStream

This line fails:

   data = insertTime(dataIn.data.AIN0, st, 1 / scanRate)

if I change:

dataIn.data.AIN0

to something else like AIN0 or some number then it runs, but its useless data of coarse.

 

This also fails:

   backlog = dataIn.ljmscanBacklog

so I just // comment it out to run.

 

What do I need to check and or fix to make "dataIn.data" function?

 

Thanks

[Ian]

I forgot to mention I'm running firmware version 1.0126

[AzeoTech]

Streaming a T7 requires DAQFactory 5.91 which will be released this week, probably later today.

[IntelSen]

In DAQFactory is there somewhere that tells you what the parameters are for various LJM functions?  For example, this is how LJM_eStreamStart(int Handle, int ScansPerRead, const int *aScanList, double * ScanRate) is defined by labjack, the signature of the function appears to be completely different in DAQFactory or at least the signature in your streaming example is different. I can't find any documentation in DAQFactory that describes your LJM interface.  

[AzeoTech]

Stream support is added in 5.91, which has not be officially released (though will be in the next day or two).  You received a prerelease version that did not have the documentation complete.  Once the release is available, you will find the proper documentation on the parameters in the help.

[IntelSen]

Installed version 5.91 went through help content including searching various stream types I could not find one reference to the stream command or it's parameters? Please excuse if I am not looking in the correct area.

[AzeoTech]

It is in section 17.8 of the user's guide.

[IntelSen]

When I start the streaming script I get the yellow triangle on the bottom of the screen. I am receiving a C1000 error message, I looked up the error code  which states:

 

"The name provided was not found:
1) Check your spelling, check for typos.
2) If you are not specifying the connection, make sure the default connection is correct."

 

I have checked my spelling for the device name and it appears to be correct. I am using the sample script provided in the latest release of the user guide. I do not see a reference to specifying the connection? Could you please assist with item 2 as it relates to the example script in user guide. I have attached a copy of my ctl program and a copy of the startStream script.

streamStart Script.txt

Rexam Stream New Script.ctl

[AzeoTech]

Ok, first, watch your indentation.  You should indent all block structures, meaning indent after while(), if(), for(), switch(), try(), etc. and then outdent when you get to the end of the block.  This is programming 101.

 

Next, I don't know what you are doing in StreamRate.  The 3rd line is not DAQFactory script, but rather part C++ header code, and part DAQFactory script.  I don't see where you actually run this sequence, but I thought I'd mention it.

 

Finally, your application runs fine for me.  The exception is that I get a "STREAM_IS_ACTIVE" error once I start the streaming.  This is because the Average channel has a Timing of 1.  You probably want that to be 0.  At 1, that means it reads that analog input every second, but once you start streaming, you can't read analog inputs on the LabJack because they are busy streaming.

 

As to the error you saw, I'd need at least a line number to examine.

[IntelSen]

Ok, good input, here is what I found the problem actually resides in the StreamRate sequence. The objective of the StreamRate sequence is to read the data rate from the T7. Here is the entire StreamRate sequence:

"while(1)
global scanrate = 0
LJ_ERROR _stdcall eGet("ANY",LJ_ioSTART_STREAM,0,@scanrate,0)
endwhile"

[AzeoTech]

eGet isn't implemented in the LJM.  In the DAQFactory form of LJM_eStreamStart, the actual scanrate is returned.  So, all you need to do is change this line:

 

device.labjackM.LJM_eStreamStart("ANY", {"AIN0", "AIN1"}, scanRate, scansPerRead, 1)

 

in your StartStream sequence to:

 

global actualScanRate = device.labjackM.LJM_eStreamStart("ANY", {"AIN0", "AIN1"}, scanRate, scansPerRead, 1)

 

Then you can access the variable actualScanRate from anywhere.