Hi All,
I'm currently working on a GNU Radio source block for the KrakenSDR. So far my block mostly seems to work as expected, but I'm having some minor issues and questions.
If you didn't know, the KrakenSDR is 5 RTL-SDR receivers, on the same clock with a noise source for coherence calibration of the channels. We're using it for applications like radio direction finding and passive radar, and mostly write our own code in Python. But having a GNU Radio source would be useful for others.
With KrakenSDR there is a DAQ software called "heimdall" which handles all the coherent calibration automatically. In my source block, I'm able to successfully receive the data in the GNU Radio source block from heimdall via a socket connection.
First so you know, the heimdall DAQ buffers an array of "cpi_size" (cpi = coherent processing interval) IQ data per channel, and outputs those arrays on the socket when it's filled. By default the cpi_size = 2^20. So in my GNU Radio source I'm receiving five, 2^20 long arrays of coherent complex IQ data every ~400ms.
I believe in GNU Radio this is considered a vector? So should I make the output of the source block five port vectors, with out_sig=[(np.complex64, cpi_size)] * numChannels and set vlen to cpi_size in the yaml?
Or instead should I have it as an output stream out_sig=[np.complex64] * numChannels, and be using Stream->Vector blocks when needed, with num_items set to cpi_size?
I've tried both methods, and they both work. But I don't understand why when using the vector output implementation, the shape of output_items keeps flipping between (5, 2, 1048576) and (5, 1, 1048576)?
Code is all at
https://github.com/krakenrf/gr-krakensdr if anyone would care to take a look. Everything in Python. If anyone has any tips or comments please let me know. Thanks to anyone for your insights.