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0 pointsad8e4y ago0 comments

The scrambling is easy to see once you know it's happening: press k and l simultaneously on your Thinkpad keyboard. It'll always come out "lk" unless you deliberately separate them.

Testing was done [0], but it's not written in an easy-to-understand way. As a summary, Thinkpad keys are scrambled within 15-23 ms. Usually, humans ascribe scrambled letters to their own mistakes, but this time it's the keyboard's fault. Lenovo continues to ignore the issue.

One very stupid solution for your password is to change its letters to go from right to left. That way the scrambling will become anti-scrambling and you can type your password even faster than on a normal keyboard!

[0]: https://github.com/ad8e/input-polling-test

0 comments

stavros4y ago

Oh man, is that why pressing "iu" quickly would come out as "ui"? I know I press them correctly, because I use the middle and ring fingers together simultaneously, with the longer finger obviously striking one key first, yet they'd always come out wrong.

OneLeggedCat4y ago

Wow. All these years it's been the keyboard, not me. Kinda mildly infuriating.

stavros4y ago

Yeah, it really is, and people didn't believe me when I said with certainty that it was the keyboard's fault.

alar444y ago

Wow. I'm surprised they don't do this on the component level. When I was working in embedded, I considered software debouncing a lazy hack. I'd rather sanitize the data before it hits software.

sannee4y ago

Firstly, hardware debouncing is a bit awkward to implement on a multiplexed matrix, since you need a debouncing circuit for each of your inputs (meaning about a dozen or so of them).

More importantly though, software debouncing offers greater flexibility. For keyboards, you usually[1] want to implement an asymmetric "eager" mode, where a key press gets registered immediately and only the key release is debounced. Since software usually does stuff on the key down event, this works to reduce latency.

[1] Well, that's what the various enthusiast mechanical keyboard firmwares do, I am not so sure that generic $random_corp keyboards do care...

brokenmachine4y ago

There's nothing wrong with software debouncing. Almost all fancy DIY exotic keyboards use software debouncing effectively.

In fact it's more customizable for quicker response than hardware RC debouncing.

There is, however, something wrong with shitty debouncing software.

halpert4y ago

It looks like he keyboard state is read by the driver, rather than the keyboard sending the state to the OS. How would you denounce on a hardware level with such a setup?

gridspy4y ago

One way is a RC circuit - where the switch (the keyboard button) in series with a resistor then charges a capacitor. You specify the ratio of resistance to capacitance so it takes long enough for the switch to stop bouncing before the capacitor output rises to the sense level of your digital input.

But if you want to reduce hardware cost, you can eliminate many capacitors and resistors by doing it in firmware instead.

3 more replies

perihelions4y ago

>"The scrambling is easy to see once you know it's happening: press k and l simultaneously on your Thinkpad keyboard. It'll always come out "lk" unless you deliberately separate them."

Is there an easy way to fix this? This is a noticeable nuisance in Emacs, when chord strings get "debounced" out of order (i.e. things like C-xC-m -> C-mC-x are quite annoying). The debounce precision is slower than fast human typing. Even though keypress event order is correct and noticeably correct, it gets rounded to "simultaneous", and then reordered (backwards) according to the logic you've described.

abracadaniel4y ago

I’m always noticing the terrible denouncing times on things like appliances or garage doors, but I never thought about how it affects multiple key presses in keyboards. Fascinating to get more insight into a particular pet peeve of mine.

ohazi4y ago

This must be it, then. The key pairs / triplets that I type in most quickly are left to right.

j / k navigate · click thread line to collapse

0 comments

stavros4y ago

OneLeggedCat4y ago

Wow. All these years it's been the keyboard, not me. Kinda mildly infuriating.

stavros4y ago

Yeah, it really is, and people didn't believe me when I said with certainty that it was the keyboard's fault.

alar444y ago

Wow. I'm surprised they don't do this on the component level. When I was working in embedded, I considered software debouncing a lazy hack. I'd rather sanitize the data before it hits software.

sannee4y ago

Firstly, hardware debouncing is a bit awkward to implement on a multiplexed matrix, since you need a debouncing circuit for each of your inputs (meaning about a dozen or so of them).

[1] Well, that's what the various enthusiast mechanical keyboard firmwares do, I am not so sure that generic $random_corp keyboards do care...

brokenmachine4y ago

There's nothing wrong with software debouncing. Almost all fancy DIY exotic keyboards use software debouncing effectively.

In fact it's more customizable for quicker response than hardware RC debouncing.

There is, however, something wrong with shitty debouncing software.

halpert4y ago

It looks like he keyboard state is read by the driver, rather than the keyboard sending the state to the OS. How would you denounce on a hardware level with such a setup?

gridspy4y ago

But if you want to reduce hardware cost, you can eliminate many capacitors and resistors by doing it in firmware instead.

3 more replies

perihelions4y ago

>"The scrambling is easy to see once you know it's happening: press k and l simultaneously on your Thinkpad keyboard. It'll always come out "lk" unless you deliberately separate them."

abracadaniel4y ago

ohazi4y ago

This must be it, then. The key pairs / triplets that I type in most quickly are left to right.

j / k navigate · click thread line to collapse