[USRP-users] UHD C++ API Questions

Peter Witkowski pwitkowski at gmail.com
Mon Dec 1 18:23:02 EST 2014


Hello,

I am in the process of writing a simple RF receiving program that follows
many of the same steps as rx_samples_to file.  I am following the example
code found here:
https://github.com/GREO/uhd/blob/master/host/examples/rx_samples_to_file.cpp
.

I had a couple questions come up as I was following the example:

1.  How are errors handled by the API?  For example, when I call
uhd::usrp::multi_usrp::make()
and it fails, how do I know that the pointer points to an invalid device?
Do I check the pointer for null or is there an exception thrown?
2.  Similar question to above, how do I know that device settings are
actually set?  For example, for set_rx_rate() are any exceptions thrown if
the rate is bad, or do I just need to call get_rx_rate() immediately
afterwards?
3.  In a newer version of rx_samples_to_file (see here:
https://github.com/EttusResearch/uhd/blob/master/host/examples/rx_samples_to_file.cpp
) I noticed that a tuning request is used to set the frequency of the
device.  Is this the preferred method or does a call to set_rx_freq()
suffice?
4.  In all the example code I've been able to dig up, the connection to the
device is closed by simply exiting from the program.  Is there a way to
close the device and perform the necessary clean-up (i.e. the opposite of
make()) manually?
5.  In the two versions of rx_samples_to_file that I found, I noted a
difference in the way data is read from the device via recv().  Namely, I'm
lost on the last two parameters that are passed in.  Do I have to specify
an io_type and are there different options than RECV_MODE_FULL_BUFF?  Do I
have to use a STL vector or can I pass it a different data structure (like
a C-style buffer/array)?  I guess I just need to be pointed to a good few
lines of code on how recv() works and is implemented.  Also, does recv()
throw exceptions?

Thanks in advance for the help.

-- 
Peter Witkowski
pwitkowski at gmail.com
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