Enable RGB

config/boards/arm/mona_w/mona_w.dts

@@ -19,6 +19,7 @@
 		zmk,kscan = &kscan0;
         zmk,matrix_transform = &default_transform;
 		zmk,battery = &vbatt;
+		zmk,underglow = &led_strip;
 	};
 
 	kscan0: kscan {
@@ -92,6 +93,32 @@
 	status = "okay";
 };
 
+&spi1 {
+	compatible = "nordic,nrf-spim";
+	status = "okay";
+	mosi-pin = <5>;
+	// Unused pins, needed for SPI definition, but not used by the ws2812 driver itself.
+	sck-pin = <6>;
+	miso-pin = <8>;
+
+	led_strip: ws2812@0 {
+	compatible = "worldsemi,ws2812-spi";
+	label = "WS2812";
+
+	/* SPI */
+	reg = <0>; /* ignored, but necessary for SPI bindings */
+	spi-max-frequency = <4000000>;
+
+	/* WS2812 */
+	chain-length = <16>; /* number of LEDs */
+	spi-one-frame = <0x70>;
+	spi-zero-frame = <0x40>;
+	color-mapping = <LED_COLOR_ID_GREEN
+					 LED_COLOR_ID_RED
+					 LED_COLOR_ID_BLUE>;
+	};
+};
+
 &flash0 {
 	/*
 	 * For more information, see:

config/boards/arm/mona_w/mona_w_defconfig

@@ -19,4 +19,9 @@ CONFIG_FLASH=y
 CONFIG_FLASH_PAGE_LAYOUT=y
 CONFIG_FLASH_MAP=y
 
+# Enable Underglow
+CONFIG_ZMK_RGB_UNDERGLOW=y
+CONFIG_WS2812_STRIP=y
+CONFIG_ZMK_RGB_UNDERGLOW_EXT_POWER=y
+
 CONFIG_BUILD_OUTPUT_UF2=y