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QMK debounce masterclass

QMK contributor u/x34l explains different debounce algorithms and shares some of his measurements.

KBD.news
Published November 4, 2020
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In his post, fellow Redditor x34l sheds some light on debounce algorithms.

Hi, I'm one of the (many) devs who did debouncing code at some point for QMK – x34l.

The default debounce algorithm has some latency repercussions meaning you can get some nasty 30ms+ response times sometimes while typing.

There are a few algorithms available (eager-pr, eager-pk) that reduce latency by 5-10ms.

Do note that to get the best algorithm, you need to find out your scan rate.

If it's below 500, try eager-pr, and if its above 800, try eager-pk.

Allegedly, some keyboards such as ErgodoxEZ were plagued by latency in the default algorithm, and an eager-pr/eager-pk style debounce reduced latency by a noticeable amount.

More info:

https://docs.qmk.fm/#/feature_debounce_type

tl;dr

In rules.mk:

if you have DEBOUNCE_TYPE = CUSTOM then leave it.

Otherwise: DEBOUNCE_TYPE = sym_eager_pk or DEBOUNCE_TYPE = sym_eager_pr

Finally, here is a click latency video, using Goose Enterprises' LagMeter:

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Published on Wed 4th Nov 2020. Featured in KBD #1 (source).


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