Is there a cross reference for Datalink funtions and PI-SDK calls?
For example, Datalink has PISampDat(). What call would return the same data using PI-SDK? I assume Datalink uses the PI-SDK “under the hood”.
Most of the functions which PI Datalink have will be matched the function under PIData class in PI SDK help file. Like PIData class has Snapshot() function to retrieve snapshot value, RecordedValues() to retrieve archived values with a time range. However, there still have some differencne. Like you mentioned "Sampled Data" function. This function is located in IPIData2 class, named InterpolatedValues2().
You are right, PI Datalink is using PI SDK as "under the hood", but makes some optimization.
Please note that as of PI DataLink 2013, it has switched over to use the AF SDK under the hood.
Retrieving data ...