[Discuss-gnuradio] oQPSK mod path

[Marius]

Hi!

I'm creating a flow-graph that leverages the Wiesel 802.15.4 stack:
http://wiesel.ece.utah.edu/redmine/projects/gr-ieee802-15-4/wiki.
Mainly I want a complete GRC flowgraph for TX and RX on 802.15.4.

The C++ is:
http://wiesel.ece.utah.edu/redmine/projects/gr-ieee802-15-4/repository/revisions/master/entry/src/lib/ucla_qpsk_modulator_cc.cc
- 4 samples per symbol

So my XML definition is:
<?xml version="1.0"?>
<block>
  <name>gr_802_15_4 oQPSK</name>
  <key>ucla_qpsk_modulator_cc</key>
  <category>802_15_4-COSA</category>
  <import>from gnuradio import ucla</import>
  <make>ucla.qpsk_modulator_cc()</make>

  <sink>
    <name>in</name>
    <type>float</type>
  </sink>
  <source>
    <name>out</name>
    <type>complex</type>
  </source>
  <doc>
Generate a QPSK signal from a +/- 1 float stream.
For each two input symbols we output 4 complex symbols with a half-sine
pulse shape.
  </doc>
</block>

The Error each time I use the demod Block in a Flow-Graph is:
  File 
"/usr/local/lib/python2.6/dist-packages/gnuradio/gr/gnuradio_core_runtime.py",
line 1504, in primitive_connect
    return _gnuradio_core_runtime.gr_top_block_sptr_primitive_connect(self,
*args)
ValueError: itemsize mismatch: sig_source_f(3):0 using 4,
qpsk_modulator_cc(2):0 using 8

While my Flow-Graph is simply Signal-Source -> oQPSK mod -> USRP2.

Could anyone give me some ideas how to solve this issue? I know that I
need to delay the Q channel and add more Blocks. But this won't help
on the vector consumption issue afaik.

Best,
Marius