@trillbilly Avoid scripting something if you can. Here's how to do it without scripting, just connecting the controls in the interface designer.
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To do it with scripting you'll need to use the setAttribute function to assign a value to the waveform attribute of the waveform generator. At the moment all you're doing in your combobox callback is calling the getId function which doesn't do anything. Also you're passing a parameter to the function which will produce an error because that function doesn't take any parameters - check the docs.
