# Questions regarding USRP N200 streaming

**URL:** <https://www.ruby-forum.com/t/questions-regarding-usrp-n200-streaming/232075>\
**Category:** GNU Radio\
**Created:** [September 16, 2014, 11:53pm UTC](https://www.ruby-forum.com/t/questions-regarding-usrp-n200-streaming/232075 "2014-09-16T23:53:17Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [September 16, 2014, 11:53pm UTC](https://www.ruby-forum.com/t/questions-regarding-usrp-n200-streaming/232075/1 "2014-09-16T23:53:17Z")

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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.

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**Author:** ![Nicholas\_Hu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/67e7ee/32.png) [@Nicholas\_Hu](https://www.ruby-forum.com/u/Nicholas_Hu)\
**Post date:** [September 17, 2014, 4:52pm UTC](https://www.ruby-forum.com/t/questions-regarding-usrp-n200-streaming/232075/2 "2014-09-17T16:52:11Z")

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Hi Marcus,

Thank you for your explanation. It is clear to me now.

Nicholas

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**Author:** ![Nicholas\_Hu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/67e7ee/32.png) [@Nicholas\_Hu](https://www.ruby-forum.com/u/Nicholas_Hu)\
**Post date:** [September 17, 2014, 1:15am UTC](https://www.ruby-forum.com/t/questions-regarding-usrp-n200-streaming/232075/3 "2014-09-17T01:15:11Z")

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On 09/16/2014 04:57 PM, Nicholas Hu wrote:

> getting a file around 500,000,000 bytes which is reasonable ((16  
> Discuss-gnuradio mailing list  
> [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)  
> [Discuss-gnuradio Info Page](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio)  
> Nick, I think I answered this at [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) 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.

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<div class="post-metadata">

**Author:** ![Nicholas\_Hu](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/67e7ee/32.png) [@Nicholas\_Hu](https://www.ruby-forum.com/u/Nicholas_Hu)\
**Post date:** [March 2, 2015, 6:19pm UTC](https://www.ruby-forum.com/t/questions-regarding-usrp-n200-streaming/232075/4 "2015-03-02T18:19:03Z")

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