I am trying to make a simple PLL using a VCO but I get an error
“RuntimeError:flow graph has loops!”. Anyway around that?
Thanks…Tom
On Fri, Aug 09, 2013 at 07:31:58AM -0700, tom sutherland wrote:
I am trying to make a simple PLL using a VCO but I get an error
“RuntimeError:flow graph has loops!”. Anyway around that?
Nope, stock GNU Radio does not support loops. There’s plenty of PLLs
available already, though.
MB
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)
Dipl.-Ing. Martin B.
Research Associate
Kaiserstraße 12
Building 05.01
76131 Karlsruhe
Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu
KIT – University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association
Hi,
since I also had trouble with this issue at first, please allow me to
clarify this further: GNURadio does not support looping of blocks.
Inside a single block you can loop as often as you wish and that is
exactly how the available PLLs in GNURadio are made. Just search the
mailing list for more details, since this topic has been discussed a
couple of times already.
Yours
Martin
Am 09.08.2013 17:17, schrieb Martin B. (CEL):
On Wed, Aug 14, 2013 at 05:10:24PM -0400, Tom R. wrote:
Yes. From a scheduler standpoint, loops, as in traditional control
loops with some required and guaranteed delay, are incredibly
inefficient. And instead of figuring out how to support something like
that, Eric made the decision very early on to just not allow them at
all.You can use the asynchronous message passing interface to do loops.
If this is any help, there’s an example for async loops in
gr-digital/examples/ofdm/rx_ofdm.grc.
MB
–
Karlsruhe Institute of Technology (KIT)
Communications Engineering Lab (CEL)
Dipl.-Ing. Martin B.
Research Associate
Kaiserstraße 12
Building 05.01
76131 Karlsruhe
Phone: +49 721 608-43790
Fax: +49 721 608-46071
www.cel.kit.edu
KIT – University of the State of Baden-Württemberg and
National Laboratory of the Helmholtz Association
On Fri, Aug 9, 2013 at 1:02 PM, Martin L. [email protected] wrote:
Nope, stock GNU Radio does not support loops. There’s plenty of PLLs
available already, though.MB
Yes. From a scheduler standpoint, loops, as in traditional control
loops with some required and guaranteed delay, are incredibly
inefficient. And instead of figuring out how to support something like
that, Eric made the decision very early on to just not allow them at
all.
You can use the asynchronous message passing interface to do loops.
However, it’s asynchronous, so you’re not going to be building a PLL
or something like that which mathematically falls apart if you have
more than 1 sample delay in it. But you can at least use it to feed
back data/metadata/control info if you don’t need that kind of
requirement. But if you do, follow Martin and Martin’s advice and do
it inside of a block.
–
Tom
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