Enable RGB

config/boards/arm/mona_w/mona_w.dts

@@ -7,6 +7,7 @@
 /dts-v1/;
 #include <nordic/nrf52840_qiaa.dtsi>
 #include <dt-bindings/zmk/matrix_transform.h>
+#include <dt-bindings/led/led.h>
 
 / {
 	model = "mona_w";
@@ -19,6 +20,7 @@
 		zmk,kscan = &kscan0;
         zmk,matrix_transform = &default_transform;
 		zmk,battery = &vbatt;
+		zmk,underglow = &led_strip;
 	};
 
 	kscan0: kscan {
@@ -68,6 +70,12 @@
         >;
     };
 
+	ext-power {
+		compatible = "zmk,ext-power-generic";
+		label = "EXT_POWER";
+		control-gpios = <&gpio0  4 GPIO_ACTIVE_HIGH>;
+	};
+
 	vbatt: vbatt {
 		compatible = "zmk,battery-voltage-divider";
 		label = "BATTERY";
@@ -92,6 +100,32 @@
 	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