Building SVXLink from Master branch to RPi - questions

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Building SVXLink from Master branch to RPi - questions

Erik Finskas-2
Hello all.

Whilst building SVXLink from Github master branch to a RPi2 or 3 there are optimization related thing which I'd like to understand better.
The OS release used is Rasbian Jessie lite 04-2017

The tips page to build on a RPi at https://github.com/sm0svx/svxlink/wiki/InstallSrcHwRpi instructs to set RELEASE_FLAGS accordingly to a makefile.cfg -file.

There seems to be no such thing (anymore?) as the build engine is cmake, which has the similar options in the Cmakelist.txt -file.

The original fileset has the flags set like this: set(CMAKE_C_FLAGS_RELEASE "-O3")

When changed to what the github page recommends, set(CMAKE_C_FLAGS_RELEASE "-g -O2 -mfloat-abi=softfp -mfpu=vfp -mcpu=native")
the compilation fails on its very first steps due to the softfloatingpoint instruction;

[  1%] Building CXX object async/core/CMakeFiles/asynccore.dir/AsyncApplication.cpp.o
In file included from /usr/include/features.h:398:0,
                 from /usr/include/arm-linux-gnueabihf/sys/types.h:25,
                 from /home/svxlink/svxlink/src/async/core/AsyncApplication.cpp:38:
/usr/include/arm-linux-gnueabihf/gnu/stubs.h:7:29: fatal error: gnu/stubs-soft.h: No such file or directory
 # include <gnu/stubs-soft.h>
                             ^
compilation terminated.
async/core/CMakeFiles/asynccore.dir/build.make:62: recipe for target 'async/core/CMakeFiles/asynccore.dir/AsyncApplication.cpp.o' failed

When the option is changed to -mfloat-abi=hard the compilation succeeds

There's a comprehensive explanation of the different flavours of floating point support at https://www.raspberrypi.org/forums/viewtopic.php?t=7796&p=99844 but for me that is high over the head mostly. What I do understand is that this also depends on the ARM release.

Now when running a test setup with just 1 RX and TX compiled with the -mfloat-abi=hard -option, the CPU consumption is about 10-15% on a RPi2

73
Erik OH2LAK

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