Debounce API

Debounce algorithm

QMK supports multiple debounce algorithms through its debounce API.

The logic for which debounce method called is below. It checks various defines that you have set in

ifneq ($(strip $(DEBOUNCE_TYPE)), custom)

Debounce selection



What else is needed

Not defined

Use the default algorithm, currently sym_g



Use your own debounce code

SRC += debounce.c add your own debounce.c and implement necessary functions


Use another algorithm from quantum/debounce/*


Regarding split keyboards: The debounce code is compatible with split keyboards.

Use your own debouncing code

  • Set DEBOUNCE_TYPE = custom.

  • Add SRC += debounce.c

  • Add your own debounce.c. Look at current implementations in quantum/debounce for examples.

  • Debouncing occurs after every raw matrix scan.

  • Use num_rows rather than MATRIX_ROWS, so that split keyboards are supported correctly.

Changing between included debouncing methods

You can either use your own code, by including your own debounce.c, or switch to another included one. Included debounce methods are:

  • eager_pr - debouncing per row. On any state change, response is immediate, followed by locking the row DEBOUNCE milliseconds of no further input for that row.

    For use in keyboards where refreshing NUM_KEYS 8-bit counters is computationally expensive / low scan rate, and fingers usually only hit one row at a time. This could be

    appropriate for the ErgoDox models; the matrix is rotated 90°, and hence its "rows" are really columns, and each finger only hits a single "row" at a time in normal use.

  • eager_pk - debouncing per key. On any state change, response is immediate, followed by DEBOUNCE milliseconds of no further input for that key

  • sym_g - debouncing per keyboard. On any state change, a global timer is set. When DEBOUNCE milliseconds of no changes has occured, all input changes are pushed.