Reading from USRP

Hey guys,

I’ve been trying to read from the USRP by simply doing u->read(buf,
512, overrun). I used the usrp_inband_usb_packet class to extract the
payload size and the payload from each USB packet received. As I
understand, the USB packets contain pairs of I and Q for each (I
didn’t change the format from the default). I was expecting the
payload size then to be a multiple of 4, since it is 2 shorts. I
frequently see payload sizes such as 7, 13, etc. What is going on
here? Are there examples of getting the data from a dbsrx using this
method and processing it? I found the test_standard_rx example, but it
doesn’t do any processing and just reads.

Thank you.


Cheers,
Timur

On Sunday 12 July 2009 08:09:24 Timur Alperovich wrote:

method and processing it? I found the test_standard_rx example, but it
doesn’t do any processing and just reads.

If you want to use the inband code, of course you have to use the inband
firmware as well. Most probably, you use the standard firmware, and the
“payload size” you see is a normal sample.

USB packets produced by the standard firmware always contain 512
bytes/128
complex samples (as long as you stick to standard sample resolution of
16 bit
per component).

The inband firmware will produce packets containing 504 bytes of payload
(126
samples), and it will accept shorter packets.

Regards,

Stefan


Stefan Brüns / Bergstraße 21 / 52062 Aachen
phone: +49 241 53809034 mobile: +49 151 50412019

here? Are there examples of getting the data from a dbsrx using this
method and processing it? I found the test_standard_rx example, but it
doesn’t do any processing and just reads.

If you want to use the inband code, of course you have to use the inband
firmware as well. Most probably, you use the standard firmware, and the
“payload size” you see is a normal sample.

Thank you Stefan. That definitely explains it! What is the
advantage/reason for using the inband firmware? I was working on
adapting some of the OpenBTS code for what I’m trying to do and I
didn’t realize they’re using the inband firmware and didn’t realize
the differences in the data returned by the different firmware.
Searching gnuradio.org, I couldn’t find anything on the wiki about it.

USB packets produced by the standard firmware always contain 512 bytes/128
complex samples (as long as you stick to standard sample resolution of 16 bit
per component).

The inband firmware will produce packets containing 504 bytes of payload (126
samples), and it will accept shorter packets.

Regards,

Stefan


Cheers,
Timur

On Sun, Jul 12, 2009 at 2:55 PM, Timur Alperovich[email protected]
wrote:

here? Are there examples of getting the data from a dbsrx using this
didn’t realize they’re using the inband firmware and didn’t realize
the differences in the data returned by the different firmware.
Searching gnuradio.org, I couldn’t find anything on the wiki about it.

Ok, I found the information about in-band signaling, which render my
other questions moot: http://gnuradio.org/trac/wiki/InBandSignaling.
Thanks for the help again.

USB packets produced by the standard firmware always contain 512 bytes/128
complex samples (as long as you stick to standard sample resolution of 16 bit
per component).

The inband firmware will produce packets containing 504 bytes of payload (126
samples), and it will accept shorter packets.

Regards,

Stefan


Cheers,
Timur

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs