Forum: GNU Radio right source to input message

I want to transmit message over air and here is my .grc file

I need help in finding the right source for my encoder.I have 'pad
source','message source' and 'socket message'..Please help me in giving 
the
right input source to the encoder.When i connect the pad source it gave 
me
an error that is shown in the screen shot.

Thanks.
input_msg_tx.png
<http://gnuradio.4.n7.nabble.com/file/n40059/input_...

On 03/07/2013 06:49 PM, manjusha wrote:
>
* Delete this: The pad source is for hierarhical blocks.
* Delete this: That message source is not related
* I recommend to reduce the amplitude of the signals sent to the usrp
source < 1.0 magnitude

* You do not need to feed the input of the message socket block - that
is for writing to the socket. You would probably connect a packet
deframer from the receive chain there.

Your flow graph is ready, if you write a packet into this socket, it
will transmit something.

-josh

Thanks for your reply josh..

I only have the message socket block now.But still i get the attached
error..

And,you were suggesting an amplitude < 1 which i am not aware of..can 
you
please explain.
Also,i am using a trying to transmit a message so why do i need a packet
deframer?


thanks.. tx_message_socket.png
<http://gnuradio.4.n7.nabble.com/file/n40062/tx_mes...
manjusha,

* Delete this: The pad source is for hierarhical blocks.
* Delete this: That message source is not related
* I recommend to reduce the amplitude of the signals sent to the usrp
source < 1.0 magnitude

* You do not need to feed the input of the message socket block - that
is for writing to the socket. You would probably connect a packet
deframer from the receive chain there.

Your flow graph is ready, if you write a packet into this socket, it
will transmit something.


the pad source is for making hierarchical blocks, you probably dont want
this.

There are 3 ways to get data into that packet encoder from gr extras.

* A message socket block
* The stream to blob block
* A custom block that outputs message blobs

On 03/07/2013 07:21 PM, manjusha wrote:
> Thanks for your reply josh..
>
> I only have the message socket block now.But still i get the attached
> error..
>

This "Preload>=0" that you sent to the other mailing list?

No idea, i couldnt find the error in gnuradio source or grextras source.
Is there any more verbose for that error?

> And,you were suggesting an amplitude < 1 which i am not aware of..can you
> please explain.

An amplitude of 1.0 scales to the full range of the DAC. You dont want
to be sending samples that would be clipping. So be careful of the
amplitude of your signal on the output of the filter block.

> Also,i am using a trying to transmit a message so why do i need a packet
> deframer?
>

Well, you dont need a deframer.

It seemed you were searching for something to connect to the input port
of that block. One of the known use cases is a deframer block.

-josh

Opening a USRP1 device...
-- Using FPGA clock rate of 64.000000MHz...
>>> gr_fir_ccc: using SSE
>>> gr_fir_ccf: using SSE
Traceback (most recent call last):
  File "/home/aklilu1/gnuradio/grc/Project/top_block.py", line 82, in
<module>
    tb.Run(True)
  File
"/usr/local/lib/python2.7/dist-packages/grc_gnuradio/wxgui/top_block_gui.py",
line 76, in Run
    self.start()
  File 
"/usr/local/lib/python2.7/dist-packages/gnuradio/gr/top_block.py",
line 97, in start
    self._tb.start(max_noutput_items)
  File
"/usr/local/lib/python2.7/dist-packages/gnuradio/gr/gnuradio_core_runtime.py",
line 1976, in start
    return _gnuradio_core_runtime.gr_top_block_sptr_start(self,
max_noutput_items)
RuntimeError: gr_buffer_add_reader: nzero_preload must be >= 0


josh,

That is the error i got

On 03/07/2013 08:04 PM, manjusha wrote:
> line 76, in Run
>
>
> josh,
>
> That is the error i got
>

Thats like totally not the same as "Preload>=0"!
You must set your filter taps.
Now more email for today, ok?

- signing off -

-josh

lol..thanks for your patience josh..i appreciate it..

take care..