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Old 14th July 2012, 05:02 PM
osce0 Offline
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keyboard leds blinking, keyboard unresponsive

I have this issue I've been struggling to find a cure for couple of years of using Fedora 14 64-bit Today, I found additional info, so I'd like to get an answer so I can proceed further.

Occasionally, maybe once a month, my old Win95 PS/2 keyboard would have all 3 LED lights blink twice, then become unresponsive. Everything else works (usb mouse, network, etc.) and no error messages. I would usually restart the PC and it would fix itself. But sometimes, after trying some key presses without response, another blinking twice occurs, and the keyboard then works.

Last month, I replaced it with a black PS/2 keyboard, that never had issues on a different PC (and I have the same model on a 3rd PC that never has issues).

Today, after one month of use, this black keyboard would have all LEDs blink continuously, and unresponsive. Again, everything else works, and again, no errors in dmesg output, /var/log/messages (no kernel panic or oops), or .xsession_errors. The only thing I remember doing was mis-pressing Shift and CapsLock together, which would change the keyboard layout.

This time, I logged out from gnome instead of restarting, and the blinking stopped about 5 seconds after logging out. And the keyboard then works.

My biggest question at this point: Is LED blinking only controlled by software? Can the keyboard have functionality to blink LED by itself? Or the motherboard can do that without software control? Or the BIOS?

If the answer is that only software can control LED blinking, then I can deduce that it's not the hardware problem (at least not the keyboards), so the next time this happens, I can kill each program one by one to find out who is the culprit.

I'm trying to check if the problem is some bug in gnome/x11, or firefox/flash, or nepomuk/kmail (those were the only major programs running after the first boot about an hour prior to the keyboard problem), or keyboard driver/layout software, or a memory fault/power supply/keyboard connector/capacitor problem (hopefully not, since I had replaced with a new brand power supply a few months ago and I clean out dust regularly inside the PC.)
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Old 15th July 2012, 01:07 PM
george_toolan Offline
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Re: keyboard leds blinking, keyboard unresponsive

What kind of keyboard is this?

Maybe the ps/2 keyboard controller is broken?

Try a usb keyboard instead.
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Old 21st October 2012, 07:14 PM
osce0 Offline
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Posts: 169
Re: keyboard leds blinking, keyboard unresponsive

I recently had a spat of keyboard LEDs (all three) blink on/off then on/off for one second every few 10's of minutes (pretty random). It really didn't matter whether I used Fedora 14 PC or Fedora 17 PC, or whether I used KVM keyboard switch or not. It doesn't actually blink continuously, it seems to be on->off about 10ms, 1 second delay, then on->off about 10ms.

The only consistency seems to be that I was running firefox (flash video had been run at least once), using PS/2 keyboards.

I tried 2 different PS/2 keyboards on two different Asus PCs. The graphic cards are also different (one uses open source ATI driver and one uses proprietary nvidia driver) on those two PCs. It seems highly unlikely that two PS/2 keyboards and/or two PS/2 controllers or any combination of those two are all broken.

I searched the internet and kernel i8042_panic_blink looked like a possibility, but the source code only shows two LEDs blinking (not all 3 LEDs), and it shouldn't blink just twice.

It doesn't lock up the keyboard as long as I don't press any key during the 1second interval, but if I do happen to press any key during that time, sometimes it creates havoc, like Shift being stuck, no more key input is processed, etc. The mouse works.

So what is responsible for these 3 LEDs blinking twice for one second? Asus Motherboards, xorg, kernel?

Last edited by osce0; 21st October 2012 at 07:17 PM.
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Old 11th June 2017, 03:43 PM
osce0 Offline
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Posts: 169
Re: keyboard leds blinking, keyboard unresponsive

Sorry for the bandwidth, but I was in the process of marking all my old threads "solved" if I can, so I'm adding some resolution to this thread before marking it solved. (It'd've been nice to be able to move your own threads to some "ancient archive" group.)

I eventually searched the internet and found some pointers regarding the hardware and communications between OS, PC, and keyboard. One site that was useful was http://www.computer-engineering.org/ps2keyboard/
I'm no hardware engineer but sometimes these knowledge help to troubleshoot things so I don't end up wasting time and resources.

Basically, I'm inclined to think it was a hardware issue (most probably old power supply not keeping up with demands with memory and video) and the flashing LEDs was an error response from the keyboard encoder, not from OS or application or PC keyboard controller. There is no spec on the keyboard encoder, but there doesn't seem to be any software logic or keyboard controller logic that makes LEDs flash in this way, so that's the conclusion I came up with.

I've since upgraded my old PC and I no longer have any PS/2 keyboards. I'm just glad the PC lasted that long (almost 10 years) although I still have age>10 year old laptop functioning as test machine for latest Fedora.
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Old 11th June 2017, 04:09 PM
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Re: keyboard leds blinking, keyboard unresponsive

Hokay, I'll move this one too. EOL. BTW, if you want/need a thread moved, just check for an Admin who's online and PM him to have it done.
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