About

This supports sharing a monitor and Bluetooth keyboard between 2 Macs.

Many modern Bluetooth keyboards allow you to connect to multiple computers and select the current one via a keyboard shortcut.

For example, I use a version of this Keychron K1 keyboard and can use the "fn-1" and "fn-2" key combinations to connect the keyboard to my work or personal Mac.

I have both computers connected to a monitor with multiple inputs. With bluekvm installed on each computer, whenever I switch the keyboard to a computer it automatically switches the monitor input to that computer as well.

Ideally, you could also switch your Bluetooth mouse (or trackpad) when the keyboard connects too; however I have not been able to get blueutil to do that. The Mac OS does not let you connect the device to another computer unless you first unpair with the other and I haven't figured out how to do that and then pair automatically with the other. For now I have two pointer devices and just physically switch them when shifting focus.

Install

You will need to do this on each computer you want to control.

Monitor Input Selection

We rely on ddcctl (on Intel Macs) or m1ddc (on M1 Macs) to switch the active input. Ideally we would have one utility that worked on both flavors of Macs.

ddcctl

Only if on Intel hardware: To install ddcctl, just do:

brew install ddcctl

m1ddc

Only if on M1 hardware: To install m1ddc, just do:

brew install m1ddc

blueutil

To monitor Bluetooth connections we will use blueutil.

To install this, just do:

brew install blueutil

bluekvm

The logic of this script is very simple -- wait for the specified device (the keyboard) to connect and then switch the monitor input to this computer.

First, determine the MAC address of your keyboard and the choice of input for the computer.

1. List the paired devices:

   blueutil --paired
   

   Find the line for your keyboard and copy the MAC address, e.g.

   address: dc-2c-26-d6-41-d2, connected (slave, -58 dBm), not favourite, paired, name: "K1-keyboard", recent access date: 2020-12-24 17:00:44 +0000
   

2. Determine the input you want for this computer:

   The most common choices are these:

   Input Source	Value
   DisplayPort-1	15
   DisplayPort-2	16
   HDMI-1	17
   HDMI-2	18

   See the full table at ddcctl

3. Create a configuration file in /usr/local/etc/bluekvm.rc:

   keyboard=dc-2c-26-d6-41-d2
   display1=18
   

   Where the keyboard value is copied from the paired keyboard listed by blueutil and the display1 value is selected from the ddcctl table. If you want a second display to also be switched, add another entry like this: display2=18

4. Copy the bluekvm.sh script to /usr/local/bin:

   cp bluekvm.sh /usr/local/bin
   

5. Test the script:

   Run it manually on each computer and switch your keyboard back and forth to verify the monitor switches inputs appropriately.

   /usr/local/bin/bluekvm.sh
   

   Use ctrl-C to force it to exit when you are done.

6. Install the script as a launch daemon so that it is always running when you are logged in:

   cp bluekvm.plist ~/Library/LaunchAgents/ 
   launchctl load -w ~/Library/LaunchAgents/bluekvm.plist
   

   Verify that it is running:

   launchctl list bluekvm
   

   There should be an entry PID in the output, e.g.

   {
   	"LimitLoadToSessionType" = "Aqua";
   	"Label" = "bluekvm";
   	"OnDemand" = false;
   	"LastExitStatus" = 0;
   	"PID" = 31317;
   	"Program" = "/usr/local/bin/bluekvm.sh";
   };
   

Uninstall

To uninstall the bluekvm.sh daemon:

launchctl unload -w ~/Library/LaunchAgents/bluekvm.plist
rm ~/Library/LaunchAgents/bluekvm.plist

Copyright 2020-2023 Mike Carlton

Released under terms of the MIT License: http://carlton.mit-license.org/