What is the largest multiplexer available, and would it be suitable? I am trying to make a keyboard (and please, don't ask me to cut up an old one), so i need to cram 104 inputs onto a single 'duino. The less inputs used, the better.
Dam that's a lot and a lot of code dude the biggest one I no is the mega arduino and that's nit even 104
Your typical keyboard doesn't have all the keys set up as individual inputs.
What it does have is the keys laid out on a grid, and when connectivity is made between a particular row and column, you know that a particular key has been pressed. Thus with just three shift registers, one on the rows, and two on the colums, you can read up to 128 keys.
Of course, this layout means that you can get into keylock where pressing certain keys together results in some keys going undetected, but if you lay out your keyboard carefully so keys which are often pressed together don't conflict with one another, then you can get it to where it's not an issue.