[Discuss-gnuradio] How to use the output of a hierarchical block in the symbols field in Correlation Estimator

Dear Mailing list subscribers,

I'm using some self-defined packet prefix(chaotic complex numbers) in my communication system. In the receiver, I use Correlation Estimator to detect the packets. It needs to know the prefix. Since the prefix are interpolated and filtered by a root raised cosine filter, I decide to build a hierarchical block to generate the prefix for the correlation estimator. The hierarchical block alone works fine. But I can't call the block in the symbols field in correlation estimator. It shows 'module' object is not callable. It makes some sense to me. 

Is there a better way to do it? I prefer using existing modules since why reinvent the wheel? Thanks.

Regards,

Edwin