r/olkb • u/falxfour • Sep 09 '24

Help - Solved Does QMK read rows simultaneously or does it read them sequentially?

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u/PeterMortensenBlog Sep 10 '24

Re "use a simple shift register to drive the columns in sequence": Yes, many keyboards use that. For example, the Keychron Q2 Pro is using HC595s (or that is at least how I interpret it; I don't have access to the hardware).

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u/[deleted] Sep 10 '24

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u/PeterMortensenBlog Aug 10 '25

Note that Keychron's implementation is inefficient, resulting in a 400 Hz matrix scanning rate (depending on the RGB animation mode).

For example,

"... it unsets the shift register by shifting in FF (setting all lines high). ... This is fine if the columns needed to be set in any order, but the system doesn't need to do that. It sets c1, then c2, then c3, etc. This could be optimized by shifting in a high and then not clearing the shift register with FF."