[Discuss-gnuradio] Trouble With UHD Tune Request

[Daniel Labarowski]

Hello,
I'm working on a C++ block which accepts a pointer to a uhd sink and 
calls the sink's set_center_frequency method to change to a new 
frequency. Set_center_frequency requires input in the form of a 
uhd::tune_request_t and returns a uhd::tune_result_t. As a bit of 
background, I generated an out of tree module with gr-modtool.py. It 
contains this block as well as two other blocks. The other blocks can be 
used in GRC but this on cannot as it requires a pointer, so I disabled 
the installation of its xml file in grc/CMakeLists.txt and will be using 
it exclusively through c++. The issue that I am having seems to be in 
accessing the libraries for UHD.

//My call to set_center_frequency, where private_UHD_Sink is a pointer 
to a UHD Sink and private_freqs is a pointer to the first member of an 
array and current_freq sets the index of the array
uhd::tune_result_t result_sink = 
private_UHD_Sink->set_center_freq(uhd::tune_request_t(*(private_freqs + 
current_freq)));

I first compiled my flowgraph without #including <tune_result.hpp> and 
<tune_request.hpp> in my source file. Surprisingly, things compile just 
fine without the two files. However, a c++ flowgraph which tries to use 
the block gives a nondescript error ("expected primary-expression before 
‘(’") on the line which instantiates my block. Using one of the other 
blocks (which share the same module) in GRC returns "ImportError: 
/usr/local/lib/libgnuradio-DL_Hitemp_Blocks.so: undefined symbol: 
_ZN3uhd14tune_request_tC1Ed".

I then thought that I would try to include the two files mentioned 
above, and of course it refused to compile because it could not find the 
files. I looked at the CMakeLists.txt file included with the tag demo 
c++ example included in gnuradio and decided to add 
include_directories(${UHD_INCLUDE_DIRS}) and 
link_directories(${UHD_LIBRARY_DIRS}) to my CMakeLists.txt file in my 
src directory. The issue seems to be that many of the cmake directory 
variables on my system were not set properly. Adding "MESSAGE(STATUS, 
"GR include path: ${GNURADIO_CORE_INCLUDE_DIRS}")" to my CMakeLists.txt 
file produces "STATUS,GR include path: /usr/local/include/gnuradio" but 
this is the only GNUradio related cmake variable I have found that seems 
to have been set properly. Adding "MESSAGE(STATUS, "UHD include path: 
${UHD_INCLUDE_DIRS}") MESSAGE(STATUS, "UHD include path: 
${UHD_LIBRARY_DIRS}")" produces "STATUS,UHD include path: STATUS,UHD 
include path: ". I was able to get the source to compile by setting the 
UHD include path absolutely (added 
"include_directories(/usr/local/include/uhd/types)" to my CMakeLists.txt 
file - but I can't seem to find the UHD_Library_Directory so I cannot 
try setting it absolutely. The program now compiles, but the same error 
is produced in GRC as well as in the c++ flowgraph. I am wondering if 
anyone has any idea how I could go about including the appropriate UHD 
libraries or what else could be causing these errors? Thanks ahead of time!

--
Dan