Trigger Data Acquisition of PCs in a Network

[professor_rumsdiegeige]

Hello!

I've got around ten computers in a network. To each computer, one or more sensors are connected. All computers use Labview as the programming language.

The data acquisition of all sensors needs to start at the same time with a tolerance of up to half a second.

My idea is to make one PC a "master" that sends a trigger via network, i.e. a MultiCast packet telling all other PCs to start the data acquisition.

How do you think about it? Would you also use a Multicast packet?

Thanks for any contributions.

Sabine Lorentz

[TechNick]

UDP is a lossy protocol so it probably isn't the best solution for this application. The simplest thing to do would be to use Shared Variables. You can have a single shared variable on the master computer and monitor this variable for a change on the client computers. If you use shared variables you don't need to get into TCP programming at all. One the client computers use the DataSocket Read VI with the option to "wait for data change". You will use a URL something like "psp:\\server_name\library_name\variable\name". Now, whenever you want all the computers to take a new measurement you simply write a new value to the shared variable on the server. The DataSocket Read VI on the clients will return a new value (which you may or may not even need) and then the program can take the measurement.

Alternatively, you can establish TCP connections between the server and the client comptuers and write a "trigger" command to each client connection in a FOR loop.