I would like to use a small Arduino board as the basis of a 10-key HID with LEDs for each key. I guess the LEDs would be able to stay on or flash or pulse depending.
I would like the LED state to be modifiable by keypresses but also the state of the computer. Thus I could press a key to induce a certain state which will be reflected by the LED but the state could be changed by another route (say with the mouse) and then this should be communicated to the Arduino to turn off the LED.
I've seen a lot of macropads/keyboards being made with Arduinos but I can't find anyone doing them with indicator lights. I'm just intent on using single-colour LEDs.
How many keys and LEDs can I attach to one of those miniature Arduino versions? Can I economise on the pins by setting up the keys in a funky way?