Hello,
I read about people making cool volume knobs for their computers. I have a PC, but am doing a project where it needs to work with a Mac. The volume up and down keys on a mac are on F11 and F12, but when I send those keystrokes to the Mac, it responds with the error sound. Any suggestions on how to do this? Thanks.
It is not really F11 and F12 that let you control the volume on a Mac. It is the "media buttons". You can find them also on some "non mac keyboards" (often with symbols of loudspeakers). And with these buttons you can adjust the volume even on macs.
I think it may not be so easy to use an Arduino Leonardo or Micro for this task without modification (of the library). The HID library has it's limitations.
You can try to modify the Arduino HID library like others have done: (example) http://stefanjones.ca/blog/arduino-leonardo-remote-multimedia-keys/
Or you "set" your Mac to respond to a keypress of your choice with "volume up" and "down".
I think you can also find 3rd party apps for this.