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

[Marcus Müller]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Hi Francois,

as Activecat, I'm kind of having a hard time understanidng your
requirements.
If you're emulating a hardware signal source, go for the source approach.
If you're basically taking input from anywhere and packing it into
packets of varying length, that's exactly what the PDU block
infrastructure is for:
http://gnuradio.org/doc/doxygen/page_tagged_stream_blocks.html

Greetings,
Marcus

On 20.05.2014 15:59, Francois Gervais wrote:
> Thanks Activecat you actually answered quite well to my question. I
> thought it might be better to send 0s, i'm glad you confirmed that.
> And thanks for the output algorithm.
> 
> Could you tell me more about forecast? Most of the time I need 8
> input samples to produce one byte output so I set the forecast like
> so:
> 
> ninput_items_required[0] = noutput_items*8;
> 
> It seems pretty straight forward. Is this correct?
> 
> 
> On Mon, May 19, 2014 at 9:32 PM, Activecat <address@hidden>
> wrote:
> 
>> On Tue, May 20, 2014 at 2:17 AM, Francois Gervais < 
>> address@hidden> wrote:
>> 
>>> Hi,
>>> 
>>> I'm making a block which takes bit from a bit slicer and output
>>> packets as input comes in. My block will output bytes so it can
>>> emulate a usb adapter that receives the RF signal and output a
>>> packet stream through an FTDI. That way I can use the stack
>>> that comes with the adapter without owning one. I'll use a FIFO
>>> file so other than not issuing the serail configuration the
>>> stack should be used pretty much as is.
>>> 
>>> However, I'm not sure what I should do about the the number of
>>> outputs. Let say I'm waiting for the preamble, I won't output
>>> anything. When I get the preamble and the sync I'll send a sync
>>> byte of my own. From here every 8 inputs I'll output a byte. So
>>> basically my block will output 0 or 1 output.
>>> 
>>> Can someone help me a little with the use of forecast and
>>> noutput_items in my case? Also do I need to use the
>>> consume_each function?
>>> 
>> 
>> If your block emulates a USB adapter, defines it as a source
>> block, then you don't need to touch forecast(). If your block
>> takes input from another block, then it is not source block. I
>> don't really understand your requirements.
>> 
>> The number of outputs (referred as noutput_items) is determined
>> by the scheduler, not yourself. Says, when you have X bytes to
>> send out, if X > noutput_items:  Send out noutput_items number of
>> output, and return noutput_items if X < noutput_items:  Send out
>> X number of output, and return X if X == noutput_items: (either
>> one of above)
>> 
>> When you send out a sync byte, add that to the output count.
>> 
>> When you are waiting for the preamble, you may want to send out a
>> series of zeros, rather than just producing no output. Producing
>> no output may cause the downstream blocks to become 
>> unresponsive.
>> 
>> _______________________________________________ Discuss-gnuradio
>> mailing list address@hidden 
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>> 
>> 
> 
> 
> 
> _______________________________________________ Discuss-gnuradio
> mailing list address@hidden 
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> 
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1
Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/

iQEcBAEBAgAGBQJTe2FKAAoJEBQ6EdjyzlHtrvsH/3EhTVbESphbUfNeWmZe/rNU
YYOVD7XVYVndHzstznIwvYlNVRLugjJw74pPJ0DS050b1ggc9mDK/mW4975BICau
hQQktHxN3QReWk5qKwpAx6Y/+3bVpC+phyFzZO0+1TBwHNYexsVA+Zw0mkGrOuvA
3pInPREkJxqxcMrbZZhMTYVVDfOpB5MEjxHSKOMWyAQqop2fg1ahlEwpKjVqDmmV
9NhjSbIy29kpayTcEq525ha0QPMb5bRkRiP1sw4GqHDJZSHyUR4RWYYHiVfD3CvP
/Bmx74UyS69gnP6NmMxun3OjWngpNHkJNC0lN/GGHVhz7YjwVXINuXNkbYuEVaM=
=x2qL
-----END PGP SIGNATURE-----