Hi Ali,
I really think that it would be best for you to use DAQmx for your application. You can find the DAQmx shipping examples in LabVIEW by going to: Help >> Find Examples >> Hardware Input and Output >> DAQmx >> Analog Measurements >> Voltage
Also, we have several synchronization shipping examples under Hardware Input and Output >> DAQmx >> Synchronization.
Basically, for shynchronization use the DAQmxTiming VI on the task that is on the slave board. In the DAQmxTiming, set the sample clock of the slave device to be the sample clock of the master device. You can also do the same thing for triggering. Set the digital start trigger on the slave device to be the ai/startTrigger from the master device.
We have a great synchronization tutorial online:
http://zone.ni.com/devzone/conceptd.nsf/webmain/6DC991028566309886256F990080A720
Please check it out.
Thanks,
Sal