Re: [Discuss-gnuradio] Calling a function after every N samples

[Kevin Lee]

Hello,

Thanks for the reply! More specifically, what I'm aiming for is to change frequency after transmitting some number of samples. I've tried having the sink call the set frequency commands each time 'work' is run, but that doesn't seem to help me set the length. I've tried using message passing, but that's not sufficient because that uses a sleep timer which is too inconsistent for what I'm doing. As for the vectorised data, it still doesn't time correctly since what I think the sink is doing is writing to a buffer in hardware. Though despite that, the timing result is consistent in the first method I listed. Is there a way to trigger command execution in response to specific samples? Or any way to precisely time frequency changes?

Thanks,

Kevin

On Thu, Jun 13, 2019, 4:33 PM Michael Dickens <address@hidden> wrote:

Hi Kevin - Maybe use the tagged_stream or a PDU or vectorized data? There are various ways to do what you want that will guarantee N samples that you could then trigger a function call on. The better one to use really depends on what you actually want to do once you have your N samples. - MLD

On Thu, Jun 13, 2019, at 3:32 PM, Kevin Lee wrote:

Hello all,

I'm working on a project that requires that I synchronously issue a command to the sink I wrote after processing every "N" samples. In my reading, I came to the understanding that a good way to do this would be to use tagged streams or PDUs with message passing. I've read through the Guided Tutorial Programming Topics page, so I have a basic understanding of the above concepts. Adding a tag every N samples is simple enough but I'm struggling on figuring out how to get a block to send a message as a reaction to a sample being processed, since GR blocks work in groups of samples and the 'get_tags_in_*' functions can only return tags in ranges, so that rules out tags, and message passing uses asynchronous timers. If anyone can offer any insight that would be greatly appreciated. 

Thanks for your help,

Kevin

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