Re: [Discuss-gnuradio] OFDM GRC block attempt

[Josh Blum]

>
> I'm still not entirely sure what the difference between the hier and
> hier2 versions are? Is there anywhere that discusses this? I've checked
> the wiki and the mailing list with no results.
>

The hier blocks were a way to hide a linear chain of blocks inside a
"macro block", and all blocks ultimately reside in one top level flow
graph. However, this method of doing things is being phased out of
gnuradio in favor of the hier2 blocks.

hier2 blocks offer a fully hierarchical approach. A hier2 block can
contain any number of gr blocks and hier2 blocks. These blocks may
connect to any number of input and output ports. A hier2 block is
itself, a flow graph. And the highest level hier2 block is nothing
more than a hier2 block with no IO ports, this is called gr.top_block.

hier2 blocks should offer everything that hier blocks offer, but also,
can do a lot more. The gnuradio trunk is towards the end of switching
from hier to hier2. Currently, both types of blocks work in the
gnuradio trunk, but are incompatible with one another. Also, the blks2
package is still missing some blocks that you would find in blks.

GRC uses the hier2 format, but continued to support the hier blocks
(due to some hackery) until the "incompatible trunk check in". Just
another week or so, and all the GRC blocks should be functional again.

-Josh

> Thanks,
> Dev
>