On 09/16/2014 04:57 PM, Nicholas Hu wrote:
Hi,
I am working on a USRP project. I am using a USRP N200 with a BasicRX
daughter board to perform data streaming. I am using GRC 3.6.4.1 on a
Ubuntu 12.04 machine. The USRP N200 is set to have a decimation factor
of 8 to achieve a streaming rate of 12.5 MSPS, the daughter board is
set to A:A to perform single channel real sampling. The I Q data wire
format is set to be 16 integer each, and the host data format is set
to be complex float 32. The settings above are also in the
attachments. For analyzing data, I am using Matlab R2013b on Windows
7. My question is: when I am streaming data for about 10 seconds, I am
getting a file around 500,000,000 bytes which is reasonable ((16
bits/sample I+16 bits/sample Q)*(10 seconds)*12.5 MSPS*(1/8
bytes/bits)=500 Mbytes), but when I use read_complex_binary.m provided
by GNUradio to read the file in Matlab, I am only getting half of the
expected samples (~62,500,000 samples) instead of 125,000,000 samples.
Could anyone please explain why this is happening? Doesn't 16 bits I
and 16 bits Q wire format give me 32 bits per sample? Any help would
be appreciated.
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Nick, I think I answered this at supp...@ettus.com last night.
But, you're flowing complex-floats into your file-sink. That's 64-bits
per sample (32-I 32-Q). The wire-format and CPU format a different things.
A UHD source will translate to complex-float, because that's the
"natural" format within Gnu Radio flow-graphs, but you can also ask it
to use
complex-int16 on the "host format" side, if you're just saving to a file.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
