I'm sure many Mint Plus owners have noticed the USB port, and quite a few have even hooked it up to their computer to find out what it does. Sadly, by default, it does nothing. Now before you go pressing all the buttons, here's what you should not do:
Do not press two buttons together.
(I tried again later on in the year. That time I didn't burn my unit.)
Looking online, it seems quite a few people have bricked their brand new cleaner, and so have I. I managed to get it replaced under warranty since it's actually a bug in their firmware. The code running on a Mint Plus will, when multiple buttons are pressed, attempt to light the LEDs in a way that causes the electronics to burn. When the cover is on, you won't see the magic smoke leave your robot, but it will. And when the magic smoke leaves, it will never work again. In my case, the robotic cleaner would still attempt to turn on, making the shorted of noises, but when it came to lighting the LEDs it would brownout and shut off. I had to remove the cover to see what had happened.
Now, to how to hack your Mint Plus. Um, I'll get back to you on that. There's a JTAG port on the board, that may be the only way to get at the Atmel on the board.