I have the OS X 10.11 installed and was unable to upload to my Arduino board. I always got stuck with the error code
avrdude stk500_getsync() not in sync resp=0x00
After installing the FTDI driver it didnt't work either. So I figured out Apple provides it's own FTDI driver kernel extension since OS X 10.9, named AppleUSBFTDI.kext. So the AppleUSBFTDI kernel extension interferes with the FTDI driver. An USB port shows up in the Arduino Application, but no communication involving avrdude is possible.
Solution (without modifying or disabling any system security options introduced in 10.11):
- Open a terminal
- Execute: sudo kextunload /System/Library/Extensions/AppleUSBFTDI.kext/ -> this will unload the Apple FTDI Kernel extension.
- Reinstall the FTDI driver
- Start the Arduino IDE, select a Com Port, the correct Arduino board
- Compile and upload your sketch to the board.
Please note that kextunload will only temporarily unload the module. When your system gets rebooted, you have to do this step again. It's possible to remove the kernel extension, but out of security reasons I don't describe how to do it in this post. If you're familiar with the console, you know how to do this :)