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09-17-2015 03:40 PM
Hey guys,
I am writing a program to snoop on the SPI communication between a microcontroller and two MAX-7221 display drivers. Essentially, I want to read the Din pin of both chips and convert the data streams into the corresponding numbers that are being displayed on the devices front pannel (each chip controls two 3 digit numbers, 6 digits in all). The data is 16 bits and contains a 4 bit address and a 4 bit code B representation of the number. I recognize both of those values in the vi, convert the code B into decimal, and use the address to combine each digit into corresponding 3 digit numbers that I can display and save to a file.
Each chip has a Din line that contains the data, a clock, and a load signal (called CS). In my vi I aquire data using the external clock signal and use a pause trigger to aquire only when CS is low. This worked perfectly for collecting data from one MAX-7221 chip, but I started to run into problems when trying to aquire data from both chips simultaneously.
Since I am using two differnt clock and trigger signals, I couldn't use a single DAQ. I had a PCI-6251 laying around and decided to use that to aquire from one chip and my original USB-6361 to aquire from the other. Aquiring data from either chip with the USB-6361 works perfectly, but when I try to aquire from both DAQs simultaneously I get Error 200452 associated with the PCI-6251 pause trigger.
I have been doing a ton of digging, but I can't seem to figure out what the issue is. The NI website says that the PCI-6251 supports pause triggering, and no matter what channel I use I still get the same error. I even tried to use other types of triggers, but no matter what I do I get Error 200452.
Thoughts?
Thanks in advance!
Colin
Solved! Go to Solution.
09-17-2015 04:16 PM
In my previous post I meant to say that there is a Din line that contains the data, a clock, and a load signal (called CS). Each chip has its own CS signal as per normal SPI functionality. I am not using different Din and clock signals, just different trigger signals. What I was trying to say was I have the clock and Din signals routed into each DAQ so I can use two separate triggers. I realized that the previous post was a bit confusing, so I wanted to clarify.
09-18-2015 05:15 PM
What different clocks are you using? Are they on the chips, or are you using the internal clock of your DAQ cards?
09-18-2015 06:10 PM
09-21-2015 05:01 PM
Have you tried turning on highlight execution to confirm that the error is coming from the pause trigger node? As you said, the device should support that property. What DAQmx driver are you using?
09-25-2015 03:49 PM
I did turn on highlight execution and the errors occur right after the pause trigger node. I updated all of my drivers to 15.1.0f1 and updated my labview version to 2014, was prevously 2010, and neither one of those corrected the problem.
09-28-2015 05:43 PM
It appears that the PCI-6251 only supports digital pause triggering on an analog task. You are using it on a digital input task. The USB 6361 supports pause triggering on both types of tasks. That's why you are getting an error.
09-28-2015 09:21 PM
Hmm interesting. Could you point me in the direction of where I can find those specifications? I am looking at getting anotther DAQ and I am curious what other DAQs support digital pause triggering on a digital task.
Thanks!
09-29-2015 03:00 PM
No problem! If you go to the data sheets for each device, under the "External Digital Triggers" section, it gives a list of the types of triggers that are supported for the different types of functions the cards do, see page 13 of each products manual. The fastest way that I found it was to just search for "pause" on each manual.
USB 6361 data sheet
http://www.ni.com/datasheet/pdf/en/ds-151
PCI 6251 data sheet
09-29-2015 03:25 PM
Awesome. Thanks agian for your help and for pointing me to the correct page of the datasheets!