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From: | Marcus Müller |
Subject: | Re: [Discuss-gnuradio] Writing own gnuradio Block, optional output port |
Date: | Wed, 16 Dec 2015 23:51:30 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
How many ports GRC enforces depends on the .xml file in your
module's grc/ folder, so you will have to add a <optional>1/<optional> to the respective <soruce> definition in your .xml. Regarding operating on out1 iff there's a second output port: you can either overwrite the check_topology()[1] method and memorize the number of output streams, or you can just use the fact that work()[2] is called with a
output_items.size(). You must NEVER write to out1=output_items[1] if there is only one stream. That would be a bug, and in most cases actually lead to a segmentation fault and cancellation of your program. Best regards, Marcus [1] https://gnuradio.org/doc/doxygen/classgr_1_1basic__block.html#aca13d6f083397aada5b44d0f349ce151 [2] https://gnuradio.org/doc/doxygen/classgr_1_1sync__block.html#a38942c5d8bee5232404ab71ada9a3956 On 16.12.2015 23:40, Charles Bridger
wrote:
I've created a signal source and want to create a second port which outputs the same signal, except one sample behind. The problem I'm having is that I don't know how to make it "optional". If I change the code in the private constructor from: [Constructor Code} ... gr::io_signature::make(1,1,sizeof(float)), .... to gr::io_signature::make(1,2,sizeof(float)), It still makes me plug something into the port when I use the block in GRC, even when I don't want to use the second output port. I don't know if my code in the work method is relevant but I address the tw output ports like this: float *out0 = (float *) output_items[0]; float *out1 = (float *) output_items[1]; for(int i = 0; i < noutput_items; i++) { out0[i] = stuff; out1[i] = stuff - 1; // <- I want that to be optional when I put the block in GRC. } I've also tried setting the io_signature::make to 1,-1,sizeof(float) but that's less than ideal and doesn't work if in GRC i set number of outputs to 1. Again thank you all for your time. Cheers, Charles |
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