One of the tasks I have to carry out at work lately is test custom Vortex86DX based boards for build defects such as malfunctioning input pins, relays, serial ports, etc. I used this as an opportunity to use python’s unittest framework. I am not writing about the unit tests themselves but how I got them to work on the Vortex86DX. We are running a fairly recent version of Linux with a customized (stripped out) Ubuntu distro on this board and it has Python-2.6 installed on it. The tests involved using GPIO ports and so I had to use some kind of module that would expose the sysio c functions such as outb,inb and iopl so Cython came to mind. I found a nice pyx file for sysio on pypi and I was set until I realized my development environment was 64 bit Ubuntu and that cross compiling using distutils as far as I know, is impossible without installing 32 bit python. So I set out to do that but compiling 32 bit python wasn’t trivial either. Thanks to some google searching, I was finally successful.
Compiling 32 bit python on 64 bit Linux host:
Once I downloaded the python source from python.org here is the command I run to successfully build python.
1 2 3 4 5 | $ CC="gcc -m32" LDFLAGS="-L/lib32 -L/usr/lib32 \ -L`pwd`/lib32 -Wl,-rpath,/lib32 -Wl,-rpath,/usr/lib32" \ ./configure --prefix=/usr/local/python32 --enable-unicode=ucs4 $ make $ make install |
This would only work if you have gcc-multilibs and all the necessary 32 bit libraries installed. It was necessary to have the –enable-unicode flag because the python on the Vortex86DX was compiled with this flag.
Using Scons to build Cython modules:
At this point, I could have used my newly installed python32 and use distutils to build the module but it didn’t occur to me until later on so I used scons. Scons understands how to build shared libraries with all the correct gcc flags so it was easier to use it than to write a makefile. Annoyingly scons adds the “lib” prefix to the libraries it builds so I had to change sysio.pyx to libsysio.pyx or else python wouldn’t import the resulting .so file.
1 2 3 4 5 6 7 8 9 | libname='libsysio' src=libname+'.c' pyx=libname+'.pyx' bld = Builder(action ='cython $SOURCE') env = Environment(BUILDERS = {'cython': bld}) cython =env.cython(pyx) SharedLibrary(libname, src, CCFLAGS='-m32',LINKFLAGS='-m32',CPPPATH='/usr/local/python32/include/python2.6') Requires(src, cython) Clean(cython,src) |
I am really new to cython and scons so I am not sure if this is the best way to build cython modules but the user guide at the cython website had a “to be completed…” entry for scons.
Using the sysio module:
Now that I had a 32 bit module, I was able to start up the python shell and toggle some pins and proceed with my unit tests.
1 2 3 4 5 6 7 8 | from libsysio import * # Refer to the vortex86dx datasheet port1dir = Device(0x99) port1data = Device(0x79) # Set all ports to output port1dir.outb(0xff) # Drive all pins high port1data.outb(0xff) |
