What are Combos in a Keyboard Firmware?

Combos are a feature that allows you to assign special functionality to combinations of key presses. Different keyboard firmwares may have different implementations and options for combos, but the basic idea is the same. Some of the common types of combos are:

Chords: Chords are combos that match keys in random order, all pressed within a short time window (usually 50ms or less). For example, you can define a chord that activates KC.ESC when you press KC.A and KC.S together.
Sequences: Sequences are combos that match keys in order, pressed within a longer time window (usually 1s or more). For example, you can define a sequence that activates KC.LWIN when you press KC.A, KC.B and KC.C in order.
Leader keys: Leader keys are special keys that start a sequence of key presses that trigger an action. For example, you can define a leader key that activates KC.LWIN when you press KC.LEAD followed by KC.A.

Combos can be useful for saving space on your keyboard, adding functionality to your keys, or creating shortcuts for common tasks. You can define combos to listen to any valid key, even internal or functional keys, like HoldTap or LayerTap . However, you need to be careful not to create conflicts or ambiguities with your combos, as they may interfere with your normal typing or gaming.

If you want to use combos on your keyboard firmware, you need to check the documentation and configuration options for your specific firmware. Some of the popular keyboard firmwares that support combos are:

KMK Firmware: KMK Firmware is an open source firmware for computer keyboards written and configured in CircuitPython. It supports chords and sequences as well as other advanced features like RGB lighting, Oleds and more.
QMK Firmware: QMK Firmware is an open source firmware for AVR and ARM based keyboards. It supports chords, sequences, leader keys and tap-dance as well as other advanced features like OLED display and MIDI support.
ZMK Firmware: ZMK Firmware is an open source firmware for computer keyboards built on the Zephyr RTOS. It supports chords and sequences as well as other advanced features like wireless split keyboards.

These are some of the keyboard firmwares that support combos. If you are interested in using combos for your keyboard or device, you can follow the getting started guide or visit the website for more information for your specific firmware.

Other features in the same space as combos:

Tap-dance: Tap-dance is a feature that allows you to assign different actions to the same key based on how many times you tap it. For example, you can define a tap-dance key that activates KC.ESC on one tap, KC.LCTL on two taps and KC.LALT on three taps.
Layer-tap: Layer-tap is a feature that allows you to assign different actions to the same key based on which layer you are in. For example, you can define a layer-tap key that activates KC.LCTL when you are in layer 1, KC.L
Hold-tap: Hold-tap is a feature that allows you to assign different actions to the same key based on how long you hold it. For example, you can define a hold-tap key that activates KC.LCTL when you hold it for 100ms.

I hope this quick introduction to combos has helped you understand the concept of combos and how they can be used to add functionality to your keyboard. If you have any questions or comments, please feel free to join our Discord and discuss keyboards and firmware.

Thanks for reading!