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Re: [Discuss-gnuradio] Queue Source not being processed by DPSK Demod Bl

From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] Queue Source not being processed by DPSK Demod Block
Date: Tue, 4 Sep 2012 10:26:02 -0400

On Mon, Sep 3, 2012 at 5:44 PM, Travis Collins <address@hidden> wrote:
> By "not processing data" I mean I look at the size of the source
> queue, which is attached to the dpsk_demod block and it just grows
> without data being removed.  I just use the queue.count() method to
> observe this.  I can even stop adding data to the message source block
> and the queue count remains the same.
> Yes I'm using the dpsk_demod supplied with GNU-Radio.  When you
> mention the modulator, that doesnt apply here correct? Since Im using
> only a demod and that should take complex data and then output packet
> bits.
> When I convert the numpy array to a large string I get segmentation
> faults now even at very low sample rates.  Here is a link to the
> flow-graph if you wanna take a look: http://pastebin.com/M2CrVPwP
> -Travis

Ah, I see my confusion. You're talking about adding to the
demodulators queue. Inserting into the message queue made me think you
were working on the modulator side. In this case, the demodulator
itself is what inserts the messages. It's your task (or, more
precisely, the application's task) to remove the messages from the
queue; in other words, the queue holds the frames created by the
demodulator/receiver chain. Look in gr-digital/python/pkt.py  in the
_queue_watcher_thread function. That's where the messages are being
popped off the queue.

The demodulator expects a stream of complex values as inputs (from,
say, a USRP source).


> On Sat, Sep 1, 2012 at 11:32 AM, Tom Rondeau <address@hidden> wrote:
>> On Fri, Aug 31, 2012 at 3:13 PM, Travis Collins
>> <address@hidden> wrote:
>>> Ive change the connected block from a dbpsk_demod to a null_sink and a
>>> file_sink and the queue is processed, but I'm still having an issue
>>> with the demod block.
>>> I believe the problem has to be with the data type conversion
>>> "processed.tostring()".  Should I convert each individual value of the
>>> numpy array to a string and append them together or is there a better
>>> way?  The numpy array itself is made up of complex data.
>>> -Travis
>> Hi Travis,
>> Can you provide more details when you say that it's not processing the
>> data? What does that actually mean? Is it not doing anything or just
>> not doing what you expect?
>> The numpy array shouldn't be a problem since you are converting it to
>> a string directly. Although make sure that what tostring() returns is
>> what you think it should return.
>> As for the dpsk modulator: is that the modulator from GNU Radio? Are
>> you basically trying to do what we do in
>> examples/narrowband/benchmark_tx.py? If so, that modulator expects
>> (packed) bits, not complex samples. It will convert the bits to
>> complex samples internally.
>> Tom

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