zmk/docs/docs/behavior/key-press.md
Pete Johanson eff1b8223b refactor(keys): Unify usage page.
* Remove need for separate `&cp` behavior, but
  keep it for now for backward compat.
* Refactor sensor inc/dec as well.
2020-11-05 14:55:40 -05:00

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---
title: Key Press Behaviors
sidebar_label: Key Press
---
## Summary
The most basic of behaviors, is the ability to send certain keycode presses and releases in response to activating
a certain key.
For reference on keycode values, see pages 83-89 of the [USB HID Usage Tables](https://www.usb.org/document-library/hid-usage-tables-12).
## Keycode Defines
To make it easier to encode the HID keycode numeric values, most keymaps include
the [`dt-bindings/zmk/keys.h`](https://github.com/zmkfirmware/zmk/blob/main/app/include/dt-bindings/zmk/keys.h) header
provided by ZMK near the top:
```
#include <dt-bindings/zmk/keys.h>
```
Doing so makes a set of defines such as `A`, `N1`, etc. available for use with these behaviors
:::note
There is an [open issue](https://github.com/zmkfirmware/zmk/issues/21) to provide a more comprehensive, and
complete set of defines for the full keypad and consumer usage pages in the future for ZMK.
:::
### Improperly defined keymap - `dtlib.DTError: <board>.dts.pre.tmp:<line number>`
When compiling firmware from a keymap, it may be common to encounter an error in the form of a`dtlib.DTError: <board>.dts.pre.tmp:<line number>`.
For instructions to resolve such an error, click [here](../troubleshooting###Improperly-defined-keymap)
## Keypad Key Press
The "keypad key press" behavior sends standard keypad keycodes on press/release.
### Behavior Binding
- Reference: `&kp`
- Parameter: The keycode usage ID from the keypad usage page, e.g. `4` or `A`
Example:
```
&kp A
```