How can I syncronize a DAQx and a signal coming from the Serial port?

[Asier_gast]

Hello to everyone,
I am trying to represent and record three different signals. Two of them are coming from the DAQx card and the other one is coming from the COM1 serial port. Anyway, i managed to represent the three signals but i don´t know whether their  adquisition is taking place at the same time or not. It is very imortant for the research that they have the same starting reference so I can see  what is the shift of their fase. I would like then to store them together and represent on the same graph.
I am very new to labview so i don´t know if i am doing it the right way. I attach snapshots of what I have done so far hoping that someone will give me some advice on how to develop this project.

[Mark_E]

Hi Asier_gast,

There is no official way to do this as there is no common timing signal between COM ports and the PCI bus. The only way to synchronize devices running on completely separate buses is to use software-timing.

I highly recommend starting with example programs that come with LabVIEW (Help » Find Examples). There are examples for DAQ found under Hardware Input and Output » DAQmx » Analog Measurements, etc. For serial, try Hardware Input and Output » Serial. The idea would be to configure all your tasks/channels, take readings on all channels inside the while loop (with a wait function to time it properly), and close all tasks/close references outside the while loop.

You could also try searching NI Developer Zone at www.ni.com/devzone. I’ve looked here for anything I couldn’t think of, but all the posts I’ve seen seem to confirm that there’s really no good solution.

Please post back if you find a way to do this for your application.