Jquery and keyboard on android and IOS

I am having trouble capturing which character the user pressed when used smartphone with ANDROID / IPHONE. I use the jQuery keyup event, but the answer is always undefined or 229.

Does anyone know how to solve this?

The code I'm using:

$('#campo-valor').on('keyup', function(event) {
   console.log(event.which);
}
Author: Sergio, 2017-04-11