Time Synchronization for multiple Arduino

Question

I made a program wherein there are 3 nodes, each node measure temperature using thermocouple. Each node has 1 arduino and 1 Xbee. All the three will send their temperature data to the base station where Xbee exists. What I want to do is All of the data will be placed in chart, it should have time and date. As shown in my VI, and if you see something that I have used incorrectly please do say. I am new to LabVIEW.
How will I synchronize the data? For each and everyone have a time and date? Say, node 1,2, and 3 took a measurement at t=0. Since they all have different location, they will all have a different received time in base station? How can I make them send their data and place the appropriate time for the temperature measurement?
Attachments:
overview.vi ‏64 KB

Answer 1

Serial communication via RS-232 is always one-to-one because there is no addressing capability. The LIFA Init VI does not have any addressing capability so it appears that none of the other communications methods allows more than one device per channel. I think you will need three separate channels (COM ports) for the three devices.
How precisely do you need the temperatures to be synchronized? I would expect that any system using XBEE will not be responding to rapid changes of the temperatures. Just assume that the three readings taken in the same loop are at the same time and append a timestamp or tick count in software. I do not have the Get All Data.vi so I canot tell how fast it executes. I would move the Write to File to a parallel loop and put a Wait in the read loop to set the loop time. For most temperature applications software timing is good enough.  What will you be doing with the data?
Lynn