Q&A: Wild Trackpad

Q For several months, I had an Apple Wireless Keyboard working fine with my MacBook Pro, the latter sitting on a clear plastic platform several inches above the keyboard. But when I added a Magic Trackpad, the combination is a nightmare, with the cursor sometimes taking on a life of its own and flying wildly around the screen, and random repeated letters spitting out of the keyboard. What have I done to deserve this?

A Something is interfering with your Bluetooth signals, so that they are becoming munged to the point where the data being transferred has become bitter and twisted; this is not a ghost in the machine!

The most likely cause is a combination of your Bluetooth devices being low down, losing line-of-sight from the aerial built into your MacBook Pro, the fact that you have two devices, and the Magic Trackpad generating plenty of Bluetooth traffic when in use. As with other computer wireless systems, Bluetooth is digital, so in theory should either work properly or not at all, but in practice these unconventional layouts seem capable of generating spurious traffic, resulting in wild cursor movement and keyboard weirdness.

Try putting your MacBook Pro, keyboard, and Magic Trackpad on the same level surface, and these oddnesses should vanish as mysteriously as they came. Swapping out the trackpad with a wired mouse will likewise bring the keyboard back into control. Putting objects in the way, between the Mac and peripherals, or close to your keyboard or trackpad can also make things worse. This seems to be a constraint of Bluetooth.

Updated from the original, which was first published in MacUser volume 27 issue 14, 2011.