Output Selection Behavior

Summary#

The output behavior allows selecting whether keyboard output is sent to the USB or bluetooth connection when both are connected. This allows connecting a keyboard to USB for power but outputting to a different device over bluetooth.

By default, output is sent to USB when both USB and BLE are connected. Once you select a different output, it will be remembered until you change it again.

Powering the keyboard via USB

ZMK is not always able to detect if the other end of a USB connection accepts keyboard input or not. So if you are using USB only to power your keyboard (for example with a charger or a portable power bank), you will want to select the BLE output through below behavior to be able to send keystrokes to the selected bluetooth profile.

Output Command Defines#

Output command defines are provided through the dt-bindings/zmk/outputs.h header, which is added at the top of the keymap file:

#include <dt-bindings/zmk/outputs.h>

This allows you to reference the actions defined in this header:

Define	Action
`OUT_USB`	Prefer sending to USB
`OUT_BLE`	Prefer sending to the current bluetooth profile
`OUT_TOG`	Toggle between USB and BLE

Output Selection Behavior#

The output selection behavior changes the preferred output on press.

Behavior Binding#

Reference: &out
Parameter #1: Command, e.g. OUT_BLE

Examples#

Behavior binding to prefer sending keyboard output to USB
```
&out OUT_USB
```
Behavior binding to prefer sending keyboard output to the current bluetooth profile
```
&out OUT_BLE
```
Behavior binding to toggle between preferring USB and BLE
```
&out OUT_TOG
```