Re: [Discuss-gnuradio] Help with rx_sample_to_file.cpp program and modulation scheme change in UHD

[Josh Blum]

On 09/20/2011 10:25 AM, shantharam balasubramanian wrote:
> Hi
> 
> I am pretty new to UHD. I was looking for some example programs which
> can send and receive a text file, and I came across two programs in
> the website
> (http://code.ettus.com/redmine/ettus/projects/uhd/repository/revisions/master/show/host/examples)
> named rx_samples_to_file.cpp and tx_samples_to_file.cpp.
> 
> I ran these programs in USRP1. and gave the following arguements:
> 1)./tx --rate 500000 --freq 10000000  --file rr.txt[this is the name
> of the file i transferred]
> 2)./rx --rate 500000 --freq 10000000 --file r1.txt[this is the name of
> the file where i store the received text]
> 

Those files are supposed to contain baseband samples.

> When I tried to transmit and receive some sample text files, the
> sender transmitted it correctly, but the receiver is not receiving
> anything. When I opened the received file, I found that the file was
> more than 10MB and there were some gibberish text in the file. The
> programs specify in the help options that they transmit and receive
> binary samples, so I don't know if I am working with the correct
> programs or if I am giving the correct arguments while running them.
> 

You have scared me.

> I also need to change the modulation schemes for different channel
> environments. Actually, I am working on adaptive modulation schemes in
> my experiments. However, I don't find an option to change the
> modulation schemes in UHD. (I saw those options in python based
> non-uhd codes, e.g. benchmar_Rx and benchmark_Tx). Are there any
> programs like that in UHD codes that allow change of modulation
> schemes?
> 

Gnuradio implements many modulation schemes. UHD provides an interface
to send/recv baseband samples. You should use gnuradio w/ UHD to
implement a receiver and transmitter chain.

I highly recommend installing gr-uhd component and getting familiar w/
gnuradio-companion:
http://code.ettus.com/redmine/ettus/projects/uhd/wiki#Gnuradio-UHD

-Josh