I just got the software working for the slaves that acts like Synergy! With all the pixel counting too! Right now it is only on the Teensy 3.1 with the USB Host Shield. It only runs one screen, but its super fast and the mouse cursor runs off one side of the screen to the other to simulate switching. Lets get right to the video:

Side Note: I just downloaded CamStudio (Open Source). It probably needs some new codecs (ffdshow) installed, so sorry the video is 581MB, 22sec, and 10 lousy frames per second. You will have to believe me that is is much much smoother than it looks, until I can get better screen recording.

In the entire video, the mouse position is constantly estimated without any drivers or communication with the computer.

• Mouse movement is super fast!
• Left, right, and middle buttons.
• Mouse moves to center of screen one time on Teensy startup.
• No set up.
• All Win7 settings, like acceleration, work great.
• No screen switching at protected corners, size adjustable.
• Mouse cursor bumps against the left or right and hangs until you push it more.
• The size/force of the bump forces switching, and its adjustable.
• The screen simulates switching by wrapping the coursor to the other side, like Synergy would.
• The serial monitor shows x/y estimating.
• All calibration for guessing the x/y position is continous and unnoticeable.
• Mice are hot swappable.
• Just as fast as a direct connection (unnoticeable with hand and double click speed :)

Still A Lot of Work To Do:

• Set up I2C for the slaves.
• Sketch needs to be cleaned up and tested on the Teensy-LC.
• Sketch for the Teensy 3.1 as a master.

The setup, from the last log: