lotus: Implement single-zone backlight

Signed-off-by: Daniel Schaefer <dhs@frame.work>

keyboards/lotus/config.h

@@ -4,6 +4,8 @@
 
 #pragma once
 
+#include <config_common.h>
+
 #define RP2040_BOOTLOADER_DOUBLE_TAP_RESET
 #define RP2040_BOOTLOADER_DOUBLE_TAP_RESET_LED GP25
 #define RP2040_BOOTLOADER_DOUBLE_TAP_RESET_TIMEOUT 500U
@@ -22,6 +24,11 @@
 #define DRIVER_COUNT 1
 #define RGB_MATRIX_LED_COUNT 78
 
+// PWM single one backlight configuration
+// The RP2040 datasheet says GPIO25 maps to PWM channel 4B
+#define BACKLIGHT_PWM_DRIVER    PWMD4
+#define BACKLIGHT_PWM_CHANNEL   RP2040_PWM_CHANNEL_B
+
 /* define if matrix has ghost (lacks anti-ghosting diodes) */
 //#define MATRIX_HAS_GHOST
 

keyboards/lotus/halconf.h

@@ -5,4 +5,7 @@
 
 #define HAL_USE_SIO TRUE
 
+// For single-zone backlight
+#define HAL_USE_PWM TRUE
+
 #include_next <halconf.h>

keyboards/lotus/info.json

@@ -26,6 +26,9 @@
         "pid": "0x0013",
         "vid": "0x32AC"
     },
+    "backlight": {
+        "pin": "GP25"
+    },
     "rgblight": {
         "led_count": 12,
         "pin": "GP6",

keyboards/lotus/mcuconf.h

@@ -9,3 +9,7 @@
 #define RP_SIO_USE_UART0 TRUE
 #undef RP_SIO_USE_UART1
 #define RP_SIO_USE_UART1 FALSE
+
+// For single-zone backlight
+#undef RP_PWM_USE_PWM4
+#define RP_PWM_USE_PWM4 TRUE

keyboards/lotus/rules.mk

@@ -1,6 +1,12 @@
 WS2812_DRIVER = vendor
 SERIAL_DRIVER = vendor
-#RGB_MATRIX_ENABLE = false
+
+# Backlight for one variant
+BACKLIGHT_ENABLE = yes
+BACKLIGHT_DRIVER = pwm
+
+# TODO: Enable RGB matrix for one variant
+RGB_MATRIX_ENABLE = no
 RGB_MATRIX_DRIVER = IS31FL3745
 
 # Custom matrix scanning code via ADC