I want to make an AtMega or AtXMega device which will connect to a PC via a USB port and look like it is a keyboard (i.e. emulate a USB keyboard). This device will send a 5 digit number (in the form of five numeral keystrokes) into the PC USB port. The 5 digit number will then be treated just as though it were typed on the keyboard and be entered into an open WordPad document which is currently being edited in the normal way. I will also have a standard USB keypad simultaneously connected to the PC. Therefore, I can type on the keypad OR use my special device to enter numeric data into the document. But not both simultaneously.
As an example, if I were to type the five numeral keys 1,2,3,4,5 on the standard USB keyboard, they would appear in the WordPad document at the current cursor location. With this new device, when I prompt it in a certain way, it will send the same five numeral "keys" (1,2,3,4,5) and they will be entered into the WordPad document at the current cursor position exactly as if the standard keypad was sending them.
In other words, I want to emulate a certain functional subset of a standard USB keypad.
The advice and guidance I need is: What is the most time efficient way for me to approach this project?
A. Which AtMega or AtXMega chip provides the simplest hardware/software path to a solution?
B. What reference design or development board should I purchase to get me started?
C. Will I need to use Dean's LUFA "stack" to develop the required software? ( What is a "stack" in this context, anyway? )
D. Is there an existing USB Keyboard emulation project I can use as a starting point? I have searched this forum and other internet resources, but don't seem to be able to find a concise example.
Thank you in advance for any help you can provide!