IIR filter ffd taps

Hi, How is the iir_filter_ffd module used? If I give 3 feedforwardtaps
b0,b1,b2 and 2 feedback taps a1,a2 will I get transferfunction (b0 +
b1 z^-1 + b2 z^-2) / (1 + a1 z^-1 + a2 z^-2)?

Linrad (http://www.sm5bsz.com/linuxdsp/linrad.htm) transmits UDP packets
containing a some header information and a stream of I/Q samples in a
variety of formats. It seemed like an interesting exercise to use
GnuRadio and GRC to source from those packets and build some digital
receivers.

I’m new to GnuRadio and ran into some problems that maybe people on the
list can explain.

  • How to strip the header for every packet not just the first?
  • Why no int to xxx conversions? Seems like too be a hole not to
    have a workaround?
  • Are there coding examples for adding python code to top_block as a
    light weight alternative to developing a new block?
  • Labview has a wrapper block that loops over all the blocks within.
    Didn’t see that concept in GRC, did I miss it?

thanks, jeff

  • How to strip the header for every packet not just the first?

What you probably want is a block that deframes data from an input
stream and outputs a message. GRC supports message passing blocks via
message queues. Which is a bit of a hack-around, so…

At some point I would like to figure out how to do this properly in the
gnuradio framework (there is message passing supported by the scheduler)
and get that working in GRC.

  • Why no int to xxx conversions? Seems like too be a hole not to have
    a workaround?

Nobody needed them, so they were not made. Please feel free to add
missing conversion blocks push up to a branch on github or something.

  • Are there coding examples for adding python code to top_block as a

Well, it the generated top block is python code, so just open it in an
editor and go…

light weight alternative to developing a new block?

Well you can write blocks entirely in python. See the blks2impl folder
for some examples.

  • Labview has a wrapper block that loops over all the blocks within.
    Didn’t see that concept in GRC, did I miss it?

It doesnt really apply. Labview is a graphical programming environment.
GRC is a flow graph editor for connecting digital processing blocks.

-josh