As part of an overall transition to make the use of Python optional for GNU Radio application development, we are "pushing down" into C++ the API for those things that were previously only possible from Python. One of these areas is the USRP1 operation and daughterboard control. With this latest development, it is now possible to write C++ only GNU Radio applications that use the USRP1 without hacking one's own daughterboard interface driver.
However, since access from Python is still needed for Python users, the Python API for the USRP has been re-created using the SWIG wrapper generator, in the same way we do this for the rest of the GNU Radio C++ API. This has necessitated a couple very minor changes (see below) to user's Python code.
When this code is merged into the development trunk, it will replace the entire USRP Python API. As such, it is critical that this get widespread testing on all the platforms that GNU Radio supports.
INSTALLATION OF TEST BRANCH
The testing feature branch may be checked out from:
http://gnuradio.org/svn/gnuradio/branches/features/cppdb-test
Building this branch follows the same process as building the GNU Radio trunk, with some caveats:
* Do not try to install this "over" an existing GNU Radio installation. If you have compiled the GNU Radio trunk or official release from an svn checkout or tarball, and still have the source tree, perform a "sudo make uninstall" to remove the system installation before building the test branch. If you have installed from binary packages, uninstall these using your package manager. The key is to ensure all of an existing GNU Radio is removed from the system directories. If you know what you are doing, it is possible to maintain multiple installations of GNU Radio using environment variables and/or symlinks; this would continue to work for this testing version.
* The test branch adds a new dependency. We are already using the Boost shared pointer, threading and date/time libraries; this branch also now uses the Boost program options library. These are likely already installed if you have Boost supplied by your OS distribution. If you had to compile Boost from scratch, you will need recompile and reinstall, adding 'program_options' to the list of libraries to install. The GNU Radio build 'configure' step will tell you if this library is missing.
CHANGES IN THE TEST BRANCH
One goal of this API update was to remain as backward compatible as possible with existing code users have written. Unfortunately, because of slight incompatibilities, two functions have changed.
The way to obtain a daughterboard instance subdevice number has been to reference the
_which instance variable. This has changed to a function call. This is mostly commonly seen in this snippet of code:
tr = usrp.tune(self.subdev._which, self.subdev, target_freq)...which is now:
tr = usrp.tune(self.subdev.which(), self.subdev, target_freq)
The other change has been to the installed daughterboard instance array, which can be but isn't normally accessed by user code:
u = usrp.source_c()
subdev = u.db[0, 0]
...now also becomes a function call:
subdev = u.db(0, 0)
The few occasions where these changes are needed in the GNU Radio examples directory have already been changed on the branch, and testers may need to modify their code to accommodate.
TESTING AREAS/PRIORITIES
First and foremost is to make sure we haven't broken anything. This applies both to daughterboard operation (tuning, gain, etc.) and API compatibility. So please run all your usual USRP Python code and examples to make sure it all works the same.
Secondly, there are two new C++ applications which mirror the usrp_siggen.py and usrp_rx_cfile.py Python applications. These do not get installed, but may be found in the source tree after compilation at:
http://gnuradio.org/svn/gnuradio/branches/features/cppdb-test/gr-usrp/apps
These are examples of how to write C++ only applications in GNU Radio, and operate in a similar fashion to their Python counterparts. One difference is that we haven't implemented the SI unit command line parsing yet, so instead of something like '-f 16M' you'll need to put '-f 16e6'.
Finally, the new daughterboard API has actually been pushed all the way down into the non-GNU Radio libusrp library. So anyone using this library for USRP use can try out the new daughterboard code instead of what they themselves have hacked togther.
SUCESS/BUG REPORTING
Success reports should be posted to the list. Expect lots of bugs, especially in the beginning. If you run into difficulties, please post here on the list first, and include details about your setup and relevant code. If it is a bonafide new bug and we don't fix it immediately, feel free to create a new ticket in the bug system:
http://gnuradio.org/trac/queryYou will need to login to do so. The user name is 'guest', the password 'gnuradio'.
This is one of the few remaining items pending for the official 3.2 release. Your help in shaking this feature out will be greatly appreciated.
Johnathan Corgan
Corgan Enterprises LLC