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I am currently trying to do the signal processing of multiple channels in parallel using a custom source block. Up to now I created an OOT-source block which streams data for only one channel into one output perfectly fine.

Now I am searching for a way to expand this module so that it can support a higher number of channels ( = outputs of the source block; up to 64) in parallel. Because the protocol used to pull the samples pulls them all at one it is not possible to use more instances of the same source block.

Things I have found so far:

  • A pdf which seems to explain exactly what to do already but it seems that it is outdated and that this functionality is no longer supported under GNU Radio.
  • The description of a feature which should be implemented in the future.

Is there are known solution or workaround for this problem?

BStadlbauer
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1 Answers1

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Look at the add block: It has configurable many inputs!

Two different input configurations of the add block

Now, the trick here is threefold:

  1. define an io_signature as input and output that allows for adjustable numbers. If you use gr_modtool add to create a new block, your io_signatures will be filled with <+MIN_IN+>, <+MAX_IN+>, <+MIN_OUT+> and <+MAX_OUT+>. Adjust these to reflect your actual minimum and maximum in- and output port numbers. If you want to have 1 to infinity inputs, use 1, -1.
  2. in your (general_)work method, check for the number of inputs by doing something like ninputs = input_items.size(), and for the number of outputs by doing noutputs = output_items.size().

  3. (optionally, if you want to use GRC) modify the <sink>/<source> definitions in your block GRC XML:

    <sink>
        <name>in</name>
        <type>complex</type>
        <nports>$num_inputs</nports>
</sink>

num_inputs could be a block parameter; compare the add_XX block source code.

Marcus Müller
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