Numpad alt codes?

Does Linux even support alt codes? I don’t know if there’s any other “modifier plus numpad” issues that would crop up.

If you get into programming layers into the keyboard, those won’t synchronize between the main keyboard and the numpad. Any given use case can probably be solved for with the right customization, though.

I would have thought that the bios should be handling the keyboard and numpad to look like a single keyboard/numpad combined unit where both are fitted. So then using the alt key would modify the operation of the numpad.

I suspect this is what happens on machines where people are reporting (back up this thread) that plugging a separate numpad into their laptop allows the alt key to be a modifier for their numpad. Other people who say it doesn’t work for them have a bios that isn’t set up to do it.

So I suggest that a request for an additional feature for the bios should be made to FW @nrp to get the two to act as one KB when both are fitted.

Not sure it can. The devices are sitting on the USB Bus, so they’re directly communicating on the bus with the HOST controller. No way, that I know of, to have the BIOS disconnect the USB devices, talk directly to them without the OS seeing them, and then present to the OS on the USB bus a separate USB device. Maybe it’s possible, but doesn’t seem likely.

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The keyboard and numpad are standard USB devices. I don’t think the BIOS can or should try to mess with them like that. That would involve that the BIOS hacks into the USB lines and suppresses the detection of the keyboard and numpad and instead emulated another combined USB device? Or something like that. Doesn’t sound like something I’d want. A software side fix is probably easier, like a windows device driver that emulates an alt key press on the numpad when alt is pressed on the main keyboard.


I’m down for the software fix, but I have no clue how to even approach the problem.

there is a specific hid mode where the keyboard is handled by the bios, but this is an EXTREMELY LIMITED mode, and typically exhibits problems with ghosting/n-key rollover, and is not the ideal for the device to only function in.

a fully featured hid device the bios has nothing to do with once the os is running.

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Yes, you are 100% right.
The discussion about ALT codes is here, sorry everyone for the spam.


The way that 2 part usb combos work, is exactly the way they could have made it work in this scenario, its literally the exact same solution, and also, as pointed out, i and others have used alt codes on windows with the main laptop keyboard, and a usb numpad, so its not a windows limitation, its an implementation issue

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Sorry, I did not quite understand your post. Could you please clarify the implementation issue?

Has anyone managed a solution yet? I forgot all about this and tried to use an alt code today and got very annoyed when I realized I couldn’t. It very much bothers me that a $2k+ laptop can’t do what every $10 keyboard can. Do I really have to make a third alt button out of one of the other keys on the numpad?

Yep. Here

That is essentially the only way to do it, unless you want to hack up some windows helper app to fix window’s poor handling of alt codes.

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You can also do:
press Ctrl+Shift+U, then type the four-character code and press Space or Enter

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I saw that, but it doesn’t look like anyone’s tried it yet, and it didn’t sound appetizing. What does he mean by using caps lock and num lock? Does this compromise the functionality of either of those keys? I already went through the trouble of linking the backlight to the num lock to compensate for the lack of indicator light.

This seems app-dependent? It also doesn’t seem to yield the same characters.

The code to type after the CTRL SHIFT U is the hex code for any unicode char. Then press Enter to see the char.

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I don’t have a numpad or FWL16 yet, but iirc when he posted I tried out loading the pre-compiled files on a couple rp2040 dev boards.

The method used to communicate between keyboard and numpad is how I would have done it myself. In fact, I use it on my custom QMK/Vial mouse. Different code but same basic method. Ploopy co, who makes open source QMK trackballs and mice, had the method in the optional lkbm firmware for their nano trackball. It does not interfere with capslock or numlock use.

This method is used because the USB HID keyboard spec doesn’t have a normal method to do arbitrary communication directly between devices. You can communicate with the host, but not directly between devices.

Ah, I see. I was trying alt codes. OK, well at least that can help, even if I have to learn new codes.

Well then, I guess I’ll have to give it a shot! I’ll report back with results.

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Welp, it does not seem to work. When I hold alt, the caps lock LED flashes, the numpad input seems to be going somewhere, but it does not ultimately result in an alt code character being produced. The numpad itself seems to be responding to something as well. I included my modification to have the backlight indicate num lock status (2=off, 3=on) and when alt is released, the numpad backlight flickers as if num lock status is changing or something. Of course, I also tried without this modification and it still does not work, but the backlight does not flicker.

So something is happening, but it’s not resulting in an alt code. I am very motivated to make this work so I am going to study this firmware and see if I can understand what might be missing, but I wouldn’t count on that any time soon!