USB mouse/keyboard passthrough feasible?

Question

I'm looking to achieve the following:

USB HID Mouse (or Keyboard) -> [ Arduino device ] -> PC
                                       |
                                        `-> Internet

Basically, I want to connect a keyboard or mouse to an Arduino device, do some processing, send some data over the internet and then pass-through the USB data to the PC as if the Arduino wasn't even there.

My question is twofold: what hardware should I use? Right now I'm looking at the following peripherals:

• Arduino Uno R3 SMD
• Arduino Ethernet Shield
• SparkFun USB Host Shield

Since I'm a complete neophyte when it comes to Arduino, I wanted to double-check and make sure my parts will fit together as well as work towards my goal. I was also contemplating the Arduino Leonardo (since it seems to provide mouse/keyboard out-of-the-box without reflashing the firmware), but I'm not sure I understand what that decision might entail.

Which brings me to my second question: is this feasible software-wise? I found this blog which has some information about pass-through connections, but the mouse library seems to be unfinished. I'd hate to invest 150+ dollars into a project that is doomed from the start.

Thank you!

Answer 1

To connect an external USB device to AVR you need USB Host supported on AVR side. Overhelming majority of AVR chips supports USB device only. There is e.g. AT90USB1287 chip exception. It even exists an AVR USB Key 2 device which can be used instead of normal Arduino unless you want make own PCBs.

Arduino UNO Mouse HID emulates USB mouse internally in Arduino. Implementing is easy when you have USB device AVR chip using LUFA library. But it's not case using external mouse. On the other side you can use legacy serial mouse or PS/2 keyboard as workaround.