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I use "wiringPi" to talk over SPI to some device attached to "RaspberryPi".

With test application (simple user mode app) call to function wiringPiSPISetup() works well, while executed from daemon - fails. Return value is 0 (which indicates error, according to sources/samples of "wiringPi").

Test application that works correctly was written in C, when the daemon - is in C++. I know it has nothing to do with the problem. Just listed all that is different.

The question is what could prevent the wiringPiSPISetup() from working properly while called from daemon ?

I suspect that shared library of "wiringPi" fails to load due to possible library path problem. But I am not sure how to test this, given rather modest error handling capabilities of "wiringPi".

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Ok, here is the update. In order to eliminate as much details as possible I added the command line argument to my daemon process which would eliminate the daemon initialization and run the application as a plain user application. After that wiringPiSPISetup() started working correctly. So the problem has something to do with daemon itself. – opal Jan 4 at 18:28
I posted same problem of "wiringPi" author's blog link. Nothing specific so far. :(. – opal Jan 4 at 18:34
Hello, I guess I have a little progress here. If I copy shared libraries to directory where I start the daemon from it actually works. So it is clearly not a "wiringPi" problem. It has to do to daemon library path inheritance. I tried setting LD_LIBRARY_PATH and even PATH prior to daemon start. Tried starting daemon during boot time (not from shell). So far - no luck. – opal Jan 8 at 14:03

1 Answer

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I have found a solution to my problem. In fact it was my own fault. I did not check the error code value correctly. wiringPiSPISetup() returns value that is < 0 on error and 0 - on success. I have been considering the <= 0 condition as an error.

Sorry for bothering you guys.

Regards

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