GigE Vision Events

Programming Questions C-style API
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Hi @Theo,

I will reply in two steps. In this post I describe the prefered way (GenApi). Use this if the camera supports it.

As per your example I assume you got the Cust::EventLine5PulseStartTimestamp node via the camera’s device node map (NMHGetNodeMap and then NMGetNode). First we need the call back function that is called every time the node changes (in this case when a new GEV Event arrived):

void __stdcall Line5PulseStart(NODE Node, void *pPrivate);

Then you can call this code to register this callback :

  NODE hLine5PulseStartTimestamp = /* get Cust::EventLine5PulseStartTimestamp node handle as described */;

  NODECALLBACK unregisterToken = NULL;
  cvbres_t result = NRegisterUpdate(hLine5PulseStartTimestamp, &Line5PulseStart, NULL, unregisterToken);
  if(result < 0)
    ; // error handling

Instead of the NULL in the register function, you can also give it a pointer to something that brings you back to your context (e.g. a class’ this pointer).

Important Note

The hLine5PulseStartTimestamp NODE object stores the Line5PulseStart callback function. If you release the hLine5PulseStartTimestamp via ReleaseObject, the also the callback is gone. Thus keep the hLine5PulseStartTimestamp object alive as long as you need the callback.

Why is this preferred?

The GenICam Standard Features Naming Convention only standardizes the names, not the numeric values. Thus the vendors are free to change the numeric event IDs as they see fit. This normaly only happens between vendors or device series, but we have also see them change due to firmware updates. Names are safer because of the standard.

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