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Debugging libmraa {#debugging}

This page contains a few debugging tip. When filing an issue please go through this list as it's the first thing we'll ask you to do.

Finding your mraa version

Getting the exact version of libmraa you're running is really important to us. The best way to get this is to call mraa_get_version() or mraa.getVersion(). If you built from git then please tell us which commit hash you used. Mraa no longer tags itself as 'dirty' if built as a non tagged version but simply uses the latest version number listed in the top level CMakeLists.txt file. Note that you may have to wipe the build/ dir for git sha version to be absolutely correct.

Finding error logs

mraa logs pretty much everything that goes wrong to syslog. These days it'll go to the systemd journal so check with sudo journalctl -f whilst running your app or check all libmraa messages with journalctl -t libmraa. Grab all the messages from the initialisation message right up to your last one. Using a pastebin is always a good idea, I like dpaste.com. If your system does not have systemd likely your log is in /var/log/messages or a similar location.

Common errors to check for

  • Not running as a user with permissions to the physical char devices/files that require access. Check quickly if it works as root and you likely have such an issue. The log file will reflect this
  • Incorrect IO pin numbers, mraa uses physical connector pin numbering see your platform documentation for details
  • Your platform is unsupported or has been detected wrongly (logfile will show this)
  • Using the wrong pin, check pin capabilities either using the API or your platform documentation