Keyboard Builders' Digest / Tips & Tricks
QMK debounce masterclass
QMK contributor u/x34l explains different debounce algorithms and shares some of his measurements.
Published November 4, 2020
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:
Published on Wed 4th Nov 2020. Featured in KBD #1 (source).
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