The keycode you can get from the keyboard plugin.
For the character related to the code I've faced the same issue as you and started a plugin allowing to do this "translation" with a simple expression.
You can check it out here (example capx provided).
To answer the question as whether keycodes are different from a keyboard to another, I have an AZERTY keyboard and A = 65, Q = 81.
Let me know if this is different on QWERTY.
The plugin provided here is not an official/supported release and keys like "Shift" or "Escape" will return nothing but some blank space.
The space keyboard will return a "SPACE" mention because so far it's the only key I've "intercepted" and replaced so far.
Use at your own risks, no warranty whatsoever.