ADB protocol modifier keys

[apastuszak]

So, it's my understanding that ADB does not support R vs L modifier keys. Everything is treated as a left modifier key. Is there a mod you can make for these keyboards that would allow separate left and right modifier keys?

[Findecanor]

By default, the keyboards send the same key codes for left and right modifiers.

Some keyboards, such as the Apple Extended Keyboard can be switched to send different codes for the right modifier keys ... except for the Command key.

Apple Standard Keyboard (m0116 and M0118) do not support this.

From the book Guide to Macintosh Family Hardware 2nd Edition", page 309, in section about the Apple Extended Keyboard:

If your application needs to be able to distinguish the right-hand Option and Control keys
from the corresponding keys on the left side of the keyboard, you can cause the
keyboard to generate different transition codes for those keys (shown in parentheses in
Figure 8-10) by changing the value of the Device Handler ID in Keyboard register 3 from
$0002 to $0003. You can change this ID by sending a Listen Register 3 command to the
keyboard

Right Shift $7B
Right Option $7C
Right Control $7D

BTW. I once looked at a AEKII's PCB and seen that the left and right Command key switches are even wired in parallel, whereas the other keys are wired separately.