Re: [Discuss-gnuradio] Random number of output items

[Activecat]

On Tue, May 20, 2014 at 10:23 PM, Francois Gervais <address@hidden> wrote:

Sorry about that I'll try to clarify thing.

I'm using an rtl-sdr adapter to receive an RF signal. I demodulate it and send it through the MM clock recovery and bit slicer. Then the binary signal enters the block I'm talking about here. 

This block find a valid packet by matching the preamble and the sync pattern and translates the packet into another format that is understood by a software stack designed for these type of packets. 

Normally this stack would take it's input from a serial port but in my case I output the packets in the correct serial protocol through a file sink that is binded to a FIFO. 

A picture is worth a thousand words. If you attached your existing flowgraph then it helps a lot.

 

I'll take a look at the PDU block but this translation needs to be done between two very specific protocol. I don't think a generic block can achieve that.

Please be reminded that PDU and tagged stream are two different things.

There are "PUD to Tagged Stream" and also "Tagged Stream to PDU" blocks, to perform conversions.
"Tagged Stream Block" is a special block that can only take input of tagged stream; the tag of the first element must consists the packet-length information, here the default tag key is "packet_len"

PDU is used for Message Passing, I doubt you really need this in your flowgraph.

If you are sure that your custom block needs to produce output in packets (not solely bytes), then you may want to make the block output as tagged stream.  If applicable, in alternative, you may consider to use the "Stream to Tagged Stream" block. In this case, the downstream blocks may be inherited from Tagged Stream Block.

In cases other than that, you don't need tagged stream block at all.