@Maximilian-Gerhardt Thank You.

I have been fighting against an error where it looked like the linker was not finding my the shared libonioni2c.so. Your suggestion about first renaming the current files /usr/lib/libonioni2c.so to /usr/lib/libonioni2c.so.XX and /usr/lib/liboniondebug.so to /usr/lib/liboniondebug.so.XX was a good suggestion.

My error changed to libonioni2c.so not found. So it shows me the linker was finding the correct shared object but there was something wrong with that libonioni2c.so share object. then I copied the shared objecs from github https://github.com/gamer-cndg/omega2-libs and put them in /usr/lib and everything worked!!!

2 weeks I have wasted.

Now I don't know what is in those shared objects or what is different but at least I can continue building my project.

From my 2 weeks of trying everything I have concluded that the shared object libraries provided in the standard distribution for the 2+ libonioni2c.so and/or liboniondebug.so are defective.

@Maximilian-Gerhardt

// This is my main.cpp

#include <iostream>
#include <onion-i2c.h>

// confirmed /usr/include/onion-i2c.h exists
// confirmed /usr/lib/liboniondebug.so exists
// confirmed /usr/lib/libonioni2c.so exists

int main(int argc, char* argv[])
{

std::cout << "\nTest I2C Start\n" ;

int status, val;

status = i2c_readByte(0, 38, 0, &val);

std::cout << val;	

std::cout << "\nTest I2C End\n\n" ;

return 0;

}

during the linking

g++ main.o -o minitesti2c -loniondebug -lonioni2c

main.o: In function 'main':
/sources/minitesti2c/main.cpp: undefined reference to 'i2c_readByte'
/sources/minitesti2c/main.cpp: undefined reference to 'i2c_readByte'
collect2: error: ld returned 1 exit status

From the above suggestions I changed the test function to i2c_write

i2c_write(0, 56, 0, 112);

and the errors that come back are

/sources/minitesti2c/main.cpp: undefined reference to 'i2c_write'
/sources/minitesti2c/main.cpp: undefined reference to 'i2c_write'

so then I copied the files /usr/lib/liboniondebug.so and /usr/lib/libonioni2c.so to the local directory and changed the link to

g++ -L/sources/minitesti2c/ main.o -o minitesti2c -loniondebug -lonioni2c

same error(s)

so then I copied the libraries reference above from

https://github.com/gamer-cndg/omega2-libs

put them in the /sources/minitest2c/ directory

same errors(s)

I can confirm that my i2c chip is wired correctly

i2cdetect -y 0 shows device at 0x38

i2cset -y 0 0x38 0x70 works!

i2cget -y 0 0x38 works. return 0x70!

I don't know what to try next.

@larry-biscuits exactly how did you get it working? I have the exact same problem and have tried all suggestions in this post and nothing has worked.