Cross Compilation Between WiringPi Library and F'

[OwenNieuwenhuizen]

Hi everyone,
I made a component to control a 2 axis gimbal connected to a pi cam. My group and I are running a mission using a Raspberry Pi 4b and I am trying to use the WiringPi library to send PWMs to the micro servos that control the direction of the gimbal. I got the component to build, but my deployment doesn't seem to like the functions that I am using from the WiringPi library. I believe that it is a cross compilation issue. Does this sound right/how would you recommend I go about fixing this problem?
Thx.

[LeStarch]

Do you have access to the wiring-pi library? Is it an archive (.a) library, a shared-object (.so)? Additionally, what cross-compiler are you using?

There are several solutions that you might try to resolve the issue:

1. Run a toolchain with wiring-pi installed. This works best when a vendor (or raspberry pi) has given you a per-configured toolchain.
2. Create a sysroot from the RPI 4 filesystem and/or the wiring pi library. Then set the --sysroot flag when building. This works best when your cross-compiler works except for missing libraries like wiring pi.
3. Build your own tool chain. This works best when you need to change libc/libc++ versions and add libraries. Usually you do this if the cross-compile does not work correctly.
4. Build code on the RPI4. This only works with an aarch64 operating system installed on the PI. This is why F´  does not baseline this approach: PI1, PI2, and PI3 often ran 32-bit OS not the 64bit version.

If you provide more information we can try and help select one of those options.

[OwenNieuwenhuizen]

Okay thank you so much! You saved me a lot of time and headache!

[LeStarch]

Glad to hear it!

[thomas-bc]

@OwenNieuwenhuizen also note that we have some material is explaining this process of crosscompilation/running on a remote raspberrypi in the LedBlinker Tutorial

[OwenNieuwenhuizen]

I started trying to do the crosscompilation/running bit of that tutorial and ran into an issue during this step: fprime-util build aarch64-linux. I believe that this is meant to build for the x64 ARM system so that the pi can run it, but I am having an issue and this is what is outputted:

[100%] Linking CXX executable ../bin/aarch64-linux/GDep
Toolchain 'aarch64-linux' should set CMAKE_SYSTEM_NAME to 'Generic' and set
FPRIME_PLATFORM
Call Stack (most recent call first):
fprime/cmake/FPrime.cmake:29 (include)
CMakeLists.txt:13 (include)

/opt/toolchains/bin/../lib/gcc/aarch64-none-linux-gnu/10.2.1/../../../../aarch64-none-linux-gnu/bin/ld: /usr/lib/libwiringPi.so: error adding symbols: file in wrong format
collect2: error: ld returned 1 exit status
gmake[3]: *** [GDep/CMakeFiles/GDep.dir/build.make:217: bin/aarch64-linux/GDep] Error 1
gmake[2]: *** [CMakeFiles/Makefile2:5288: GDep/CMakeFiles/GDep.dir/all] Error 2
gmake[1]: *** [CMakeFiles/Makefile2:5295: GDep/CMakeFiles/GDep.dir/rule] Error 2
gmake: *** [Makefile:1339: GDep] Error 2
[ERROR] CMake erred with return code 2
(fprime-venv) root@OwenPC:/mnt/c/Users/owenn/Command/GDep#

It gives me this warning at the top:

(fprime-venv) root@OwenPC:/mnt/c/Users/owenn/Command/GDep# fprime-util build aarch64-linux
-- [python3] python3 found at: /mnt/c/Users/owenn/Command/fprime-venv/bin/python3
-- [fpp-tools] fpp-depend found at: /mnt/c/Users/owenn/Command/fprime-venv/bin/fpp-depend
-- [fpp-tools] fpp-to-xml found at: /mnt/c/Users/owenn/Command/fprime-venv/bin/fpp-to-xml
-- [fpp-tools] fpp-to-cpp found at: /mnt/c/Users/owenn/Command/fprime-venv/bin/fpp-to-cpp
-- [fpp-tools] fpp-locate-defs found at: /mnt/c/Users/owenn/Command/fprime-venv/bin/fpp-locate-defs
-- [FPRIME] Module locations: /mnt/c/Users/owenn/Command/fprime;/mnt/c/Users/owenn/Command
Linux/mnt/c/Users/owenn/Command/fprime/cmake/toolchain/aarch64-linux.cmake
aarch64-linux
CMake Warning at fprime/cmake/platform/platform.cmake:28 (message):
-- [FPRIME] Configuration module: /mnt/c/Users/owenn/Command/fprime/config
-- [FPRIME] Installation directory: /mnt/c/Users/owenn/Command/build-artifacts
-- Target build toolchain/platform: aarch64-linux/Linux
-- Including /mnt/c/Users/owenn/Command/fprime/cmake/platform/Linux.cmake
-- Requiring thread library

Any ideas?

[OwenNieuwenhuizen]

I tried using changing up the platform.cmake file to see if I could fix the problem, but I ended up reverting everything back to what it was there because it didn't seem to be working. Could my issue be another linker error or could it be something else?

[LeStarch]

/opt/toolchains/bin/../lib/gcc/aarch64-none-linux-gnu/10.2.1/../../../../aarch64-none-linux-gnu/bin/ld: /usr/lib/libwiringPi.so: error adding symbols: file in wrong format

It looks like it is linking against a local installation of wiringpi. This will be the host architecture. You'll need to figure out how to cross compile wiringpi and link to that

[LeStarch]

This discussion moved. Marking and answer for part 1.