private static extern short ps3000_set_trigger2(
     short handle,
     Channel source,
     short threshold,
     TriggerThresholdDirection direction,
     float delay,
     short autoTriggerMs);
 public void SetTrigger(Channel source, short threshold, TriggerThresholdDirection direction, float delay, short autoTriggerMs)
 {
     CheckOpened();
     CheckRet(ps3000_set_trigger2(_handle, source, threshold, direction, delay, autoTriggerMs), "ps3000_set_trigger2");
 }