ddcctl: DDC monitor controls for the OSX command line

Adjust your external monitors' built-in controls from the OSX shell:

• brightness
• contrast

And possibly (if your monitor firmware is well implemented):

• input source
• built-in speaker volume
• on/off/standby

Code adapted from DDC Panel and DDC-CI-Tools-for-OS-X.
Also see BrightnessMenulet, a nice StatusBar slider.

For more info on the DDC protocol, read HDMI – Hacking Displays Made Interesting

Install

make install

Usage

Run ddcctl -h for some options.
ddcctl.sh is a script I use to control two PC monitors plugged into my Mac Mini.
You can point Alfred, ControlPlane, or Karabiner at it to quickly switch presets.

Known Bugs / Caveats

ddcctl gets a lot of bug reports for stuff that can't be remotely debugged or fixed.
Here are the four main issues I will close out-of-hand:

MY HACKINTOSH :
You're on your own with that one.

YOUR PC MONITOR MAY SUCK AT DDC
The DDC standard is very loosely implemented by monitor manufacturers beyond sleeping the display.

• This is because Windows doesn't use brightness sensors to dim screens like OSX does —via USB, not DDC!
• Adjusting brightness, contrast, and super-awesome-multimedia-frobber-mode may not be possible.

YOUR MAC MIGHT CRASH when ddcctl changes monitor settings.
ddcctl makes blocking I2C ioctl's to the OSX kernel.

• Don't file an issue if does, I can't debug OSX kernels and display drivers.
• And don't test this out with a bunch of unsaved work open.

YOUR MONITOR MIGHT FREEZE when making settings, especially the non-brightness/contrast ones.

• Again, don't file an issue. Power cycle the monitor.
• You just have to trial-and-error what works for your hardware.

VGA cables seem to wreak havoc with DDC comms.
Use DVI/DisplayPort/Thunderbolt if you can.