My keyboard wants to talk...

July 6, 2006 12:16 PM

My keyboard has something to say...how can I listen?

I have a keyboard that, whenever a machine it is attached to reboots, sends a whole bunch of characters to the PC. Most of them are eaten up during the BIOS POST phase, but some are still spooling by the time windows is ready to put up the login dialog, and fills up the password box till it beeps a few times. From this point forward, the keyboard works OK. I can clear out the garbage it put in the password field, login, even switch PCs on the KVM via ScrollLock.

Anyone have any ideas on how I could find out what the keyboard is spewing out? I'm hoping perhaps there is a way to fool the keyboard into thinking the PC has been reset, while having focus inside an editor window or something. I want to know what the keyboard is 'writing'.

posted by nomisxid to computers & internet (14 comments total)

This PS/2 keylogger would do it for $89.

Might be obvious, but have you tried simply unplugging the keyboard and plugging it back in while in an edit window?
posted by sonofsamiam at 12:21 PM on July 6, 2006

If it's USB, you can replug. If it's PS/2 or serial, I think I recall there's a (very minor) chance of causing a short and destroying the PC.
posted by orthogonality at 12:33 PM on July 6, 2006

If it's PS/2 or serial, I think I recall there's a (very minor) chance of causing a short and destroying the PC.

Huh? In 15 years of working with computers, I've never heard that one. As an electrical engineer, I don't possibly see how you could cause a short, unless your connectors are totally fubared.
posted by sbutler at 12:38 PM on July 6, 2006

I'm with ortho on the dangers of hotplugging a PS2 device, and I'm not sure it would help anyways. Switching channels on the KVM doesn't trigger the behavior...I suspect there is some sort of startup sequence the PC sends to a keyboard, which is what's triggering the flow. Switching from a port with no PC, to a port with a PC doesn't trigger it either.
posted by nomisxid at 12:40 PM on July 6, 2006

Huh? In 15 years of working with computers, I've never heard that one. As an electrical engineer, I don't possibly see how you could cause a short, unless your connectors are totally fubared

Had a friend who had this happen on a Packard Bell circa 1995 -- fried the motherboard. I can't recall exactly what his explanation was for it, but I'll shorthand as saying it was due to some poor design choices PB had made on the motherboard that were already outdated by that time -- so it is most definitely possible, but it's super unlikely on a modern board.
posted by fishfucker at 12:46 PM on July 6, 2006

I suspect there is some sort of startup sequence the PC sends to a keyboard, which is what's triggering the flow.

Ok, another harebrained idea: I have no idea what the PS/2 protocol is like, but could you plug a cord from your PS/2 jack on the computer in question into another computer ready to accept data? You might be able to get the initiation sequence that way.

Although that would probably require a hotplug as well.
posted by sonofsamiam at 1:12 PM on July 6, 2006

I hotplug keyboards all the time. As long as a keyboard was in the PS/2 port when POSTing, you can generally switch them out while the computer is operating, for basic IO. Rarely have a technical issue with them, much less a dangerous one.

I highly suspect the KVM. In fact, I'm glad you mentioned you had one, cause it was my first thought. Mine is flaky in weird ways too, for example, when I'm using computer A when computer B is booting, computer A's mouse will drift to the top left of the screen and will require the aforementioned hotplugging of the keyboard and mouse.
posted by hoborg at 4:46 PM on July 6, 2006

Nope, not the KVM. Same keyboard causes same issue when plugged directly into a PC. Same KVM with a different keyboard, but same PCs, no issues.
posted by nomisxid at 4:50 PM on July 6, 2006

newegg has 33 new keyboards for under $10.

ortho: you can hotswap a keyboard with no problems, i've done it hundreds of times. the only thing you can't hotswap is CPU's and power cables :).
posted by Mach5 at 7:12 PM on July 6, 2006

If there was no mouse plugged in, Windows used to tell you, before the days of USB, that you could plug in a serial mouse now but you should turn off the computer before you plug in a PS/2 mouse.

There's once in my experience that hot-swapping may have either broken a keyboard or the PS/2 port, but I wasn't directly involved and I didn't make sure.
posted by TheOnlyCoolTim at 7:29 PM on July 6, 2006

Huh? In 15 years of working with computers, I've never heard that one. As an electrical engineer, I don't possibly see how you could cause a short, unless your connectors are totally fubared.

Also chiming in here; I personally fried a PII mobo (nice dual processor one w/ SCSI even =[ ) by unplugging the keyboard while it was on.

As a hardware dabbler, I really have no idea what could cause this phenomenon, though, either, and would love to know. PS/2 Keyboards use a bidi line with open-collector/pullups on either side. I also hotswap all sorts of other cables (VGA, serial, parallel, etc.) all the time. *shrug*
posted by blenderfish at 11:14 PM on July 6, 2006

Mach5, I have plenty of keyboards. I don't have to use it. I'm just curious as to what it's spitting out.
posted by nomisxid at 10:20 AM on July 7, 2006

I guess to clarify, you CAN hotswap keyboards, and most everything else -- I do that shit all the time. Hell, I've reseated PCI cards while my computer was on with no adverse effects.

However, there is or was a non-zero chance of frying your mobo. It's very very small, in my estimation, but it's not impossible. That's all my derail was about.
posted by fishfucker at 11:06 AM on July 7, 2006

Non-zero, but small; I've never done it in 20 years of doing this stuff for a living.

The "turn your computer off" thing is entirely different: if the BIOS doesn't detect a PS/2 mouse plugged in a boot, it *does not reserve IRQ 12 for that interface*, and the interface will not work at all until you reboot the machine.

Has nothing to do with power, though.
posted by baylink at 8:56 PM on July 10, 2006