LED indicators using "Smart" LED

Note: this was adapted from caksoylar's zmk-rgbled-widget to function with Smart LEDs typically used for underglow.

This is a ZMK module containing a simple widget that utilizes a string of Smart RGB LEDs. It is used to indicate battery level and BLE connection status in a minimalist way.

Features

Short video demo

See below video for a short demo, running through power on, profile switching and power offs.

rgbled_widget.mp4

Battery status

• Blink 🟢/🟡/🔴 on boot depending on battery level, with thresholds set by CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_HIGH and CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_LOW
• Blink 🔴 on every battery level change if below critical battery level (CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_CRITICAL)

Connection status

• Blink 🔵 for connected, 🟡 for open (advertising), 🔴 for disconnected profiles on boot after the battery blink, and following every BT profile switch (only on central side for splits)
• Blink 🔵 for connected, 🔴 for disconnected on peripheral side of splits

Layer state

You can pick one of the following methods (off by default) to indicate the highest active layer:

• Enable CONFIG_RGBLED_WIDGET_SHOW_LAYER_CHANGE to show the highest active layer on every layer activation using a sequence of N cyan color blinks, where N is the zero-based index of the layer, or
• Enable CONFIG_RGBLED_WIDGET_SHOW_LAYER_COLORS to assign each layer its own color, which will remain on while that layer is the highest active layer

These layer indicators will only be active on the central part of a split keyboard, since peripheral parts aren't aware of the layer information.

NOTE: There is currently an unresolved issue with CONFIG_RGBLED_WIDGET_SHOW_LAYER_COLORS - the current widget doesn't have logic to prevent resetting RGB state to before layers were changed, so as a result, any RGB settings on layers will be overwritten.

If you need layer indicators, it's recommended to use CONFIG_RGBLED_WIDGET_SHOW_LAYER_CHANGE for now until this issue is fixed.

Tip

Also see below for keymap behaviors you can use to show the battery and connection status on demand.

Installation

Add this module to your config/west.yml by adding a new entry to remotes and projects, and point your zmk source to the branch with the necessary core changes:

manifest:
  remotes:
    - name: zmkfirmware
      url-base: https://github.com/zmkfirmware
    - name: awkannan  # <-- new entry
      url-base: https://github.com/awkannan
  projects:
    - name: zmk # <-- modified entry
      remote: awkannan
      revision: develop
      import: app/west.yml
    - name: zmk-smart-rgbled-widget  # <-- new entry
      remote: awkannan
      revision: main
  self:
    path: config

For more information, including instructions for building locally, check out the ZMK docs on building with modules.

Showing status on demand

This module also defines keymap behaviors to let you show battery or connection status on demand:

#include <behaviors/rgbled_widget.dtsi>  // needed to use the behaviors

/ {
    keymap {
        ...
        some_layer {
            bindings = <
                ...
                &ind_bat  // indicate battery level
                &ind_con  // indicate connectivity status
                ...
            >;
        };
    };
};

When you invoke the behavior by pressing the corresponding key (or combo), it will trigger the LED color display. This will happen on all keyboard parts for split keyboards, so make sure to flash firmware to all parts after enabling.

Note

The behaviors can be used even when you use split keyboards with different controllers that don't all support the widget. Make sure that you enable CONFIG_SMART_RGBLED_WIDGET only for the keyboard parts that support it.

Configuration

Expand to see available configuration options

Name	Description	Default
CONFIG_RGBLED_WIDGET_INTERVAL_MS	Minimum wait duration between two blinks in ms	500
CONFIG_RGBLED_WIDGET_BATTERY_BLINK_MS	Duration of battery level blink in ms	2000
CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_HIGH	High battery level percentage	80
CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_LOW	Low battery level percentage	20
CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_CRITICAL	Critical battery level percentage, blink periodically if under	5
CONFIG_RGBLED_WIDGET_BATTERY_COLOR_HIGH	Color for high battery level (above LEVEL_HIGH)	Green (2)
CONFIG_RGBLED_WIDGET_BATTERY_COLOR_MEDIUM	Color for medium battery level (between LEVEL_LOW and LEVEL_HIGH)	Yellow (3)
CONFIG_RGBLED_WIDGET_BATTERY_COLOR_LOW	Color for low battery level (below LEVEL_LOW)	Red (1)
CONFIG_RGBLED_WIDGET_BATTERY_COLOR_CRITICAL	Color for critical battery level (below LEVEL_CRITICAL)	Red (1)
CONFIG_RGBLED_WIDGET_CONN_BLINK_MS	Duration of BLE connection status blink in ms	1000
CONFIG_RGBLED_WIDGET_CONN_COLOR_CONNECTED	Color for connected BLE connection status	Blue (4)
CONFIG_RGBLED_WIDGET_CONN_COLOR_ADVERTISING	Color for advertising BLE connection status	Yellow (3)
CONFIG_RGBLED_WIDGET_CONN_COLOR_DISCONNECTED	Color for disconnected BLE connection status	Red (1)
CONFIG_RGBLED_WIDGET_SHOW_LAYER_CHANGE	Indicate highest active layer on each layer change with a sequence of blinks	n
CONFIG_RGBLED_WIDGET_LAYER_BLINK_MS	Blink and wait duration for layer indicator	100
CONFIG_RGBLED_WIDGET_LAYER_COLOR	Color to use for layer indicator	Cyan (6)
CONFIG_RGBLED_WIDGET_LAYER_DEBOUNCE_MS	Wait duration after a layer change before showing the highest active layer	100
CONFIG_RGBLED_WIDGET_SHOW_LAYER_COLORS	Indicate highest active layer with a constant configurable color per layer	n
CONFIG_RGBLED_WIDGET_LAYER_0_COLOR	Color to use for the base layer	Black (0)
CONFIG_RGBLED_WIDGET_LAYER_1_COLOR	Color to use for layer 1	Red (1)
CONFIG_RGBLED_WIDGET_LAYER_2_COLOR	Color to use for layer 2	Green (2)
CONFIG_RGBLED_WIDGET_LAYER_3_COLOR	Color to use for layer 3	Yellow (3)
CONFIG_RGBLED_WIDGET_LAYER_4_COLOR	Color to use for layer 4	Blue (4)
CONFIG_RGBLED_WIDGET_LAYER_5_COLOR	Color to use for layer 5	Magenta (5)
CONFIG_RGBLED_WIDGET_LAYER_6_COLOR	Color to use for layer 6	Cyan (6)
CONFIG_RGBLED_WIDGET_LAYER_7_COLOR	Color to use for layer 7	White (7)
CONFIG_RGBLED_WIDGET_LAYER_xx_COLOR	Color to use for layer xx (change xx to the layer number to change)	Black (0)

Color settings use the following integer values:

Color	Value
Black (none)	0
Red	1
Green	2
Yellow	3
Blue	4
Magenta	5
Cyan	6
White	7

You can add these settings to your keyboard conf file to modify the config values, e.g. in config/hummingbird.conf:

CONFIG_RGBLED_WIDGET_INTERVAL_MS=250
CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_HIGH=50
CONFIG_RGBLED_WIDGET_BATTERY_LEVEL_CRITICAL=10

Adding support in custom boards/shields

To be able to use this widget, you need to define and enable RGB underglow as shown in the ZMK Docs

Finally, turn on the widget in the configuration:

CONFIG_SMART_RGBLED_WIDGET=y