This m-file implements a simple data acquisition gui with multiple channels and custom triggering

It demonstrates how to:

1) Use nested functions to simplify data acquisition programs

2) Use a simple GUI (a couple of pushbuttons) to start and stop data acquisition.

3) Wait for an event/trigger (like a button press) and log pre-event or pre-trigger data from multiple synchronized channels.

4) Record pretrigger data based on custom criteria. In this m-file the triggering event is a button click. However, the event could be any custom criterion (e.g., the data amplitude is greater than a threshold *and* a toggle button is enabled).
Requires: the Data Acquisition Toolbox (TM) and the Winsound adapter. It does not depend on any hardware-specific capabilities.