Backlight - New option : BACKLIGHT_CAPS_LOCK (#4769)

* [BACKLIGHT_CAPS_LOCK_INDICATOR] Use backlight toggling as Caps Lock LED

I've implemented this feature because S65-X doesn't have LED indicators
and the existing led_set_kb(usb_led) function try to use backlight as
indicator but that creates an inconsistency with backlight_config state.

- define `BACKLIGHT_CAPS_LOCK_INDICATOR` to enable Caps Lock indicator
  using backlight (for keyboards without dedicated LED)

- Don't turn off LED indicators when suspend because backlight is
  already turned off. Else led_set(0) will turn back on backlight.

- Documentation has been updated

* [BACKLIGHT_CAPS_LOCK_INDICATOR] Turn off all LED indicators except Caps Lock if BACKLIGHT_CAPS_LOCK_INDICATOR

* [BACKLIGHT_CAPS_LOCK] Rename BACKLIGHT_CAPS_LOCK_INDICATOR

* [BACKLIGHT_CAPS_LOCK] Use new IS_LED_ON method

docs/feature_backlight.md

@@ -40,6 +40,7 @@ To change the behaviour of the backlighting, `#define` these in your `config.h`:
 |---------------------|-------------|-------------------------------------------------------------------------------------------------------------|
 |`BACKLIGHT_PIN`      |`B7`         |The pin that controls the LEDs. Unless you are designing your own keyboard, you shouldn't need to change this|
 |`BACKLIGHT_LEVELS`   |`3`          |The number of brightness levels (maximum 15 excluding off)                                                   |
+|`BACKLIGHT_CAPS_LOCK`|*Not defined*|Enable Caps Lock indicator using backlight (for keyboards without dedicated LED)                             |
 |`BACKLIGHT_BREATHING`|*Not defined*|Enable backlight breathing, if hardware PWM is used                                                          |
 |`BREATHING_PERIOD`   |`6`          |The length of one backlight "breath" in seconds                                                              |
 

quantum/quantum.c

@@ -1448,6 +1448,24 @@ void led_set(uint8_t usb_led)
     //     PORTE &= ~(1<<6);
     // }
 
+#if defined(BACKLIGHT_CAPS_LOCK) && defined(BACKLIGHT_ENABLE)
+  // Use backlight as Caps Lock indicator
+  uint8_t bl_toggle_lvl = 0;
+
+  if (IS_LED_ON(usb_led, USB_LED_CAPS_LOCK) && !backlight_config.enable) {
+    // Turning Caps Lock ON and backlight is disabled in config
+    // Toggling backlight to the brightest level
+    bl_toggle_lvl = BACKLIGHT_LEVELS;
+  } else if (IS_LED_OFF(usb_led, USB_LED_CAPS_LOCK) && backlight_config.enable) {
+    // Turning Caps Lock OFF and backlight is enabled in config
+    // Toggling backlight and restoring config level
+    bl_toggle_lvl = backlight_config.level;
+  }
+
+  // Set level without modify backlight_config to keep ability to restore state
+  backlight_set(bl_toggle_lvl);
+#endif
+
   led_set_kb(usb_led);
 }
 

tmk_core/common/avr/suspend.c

@@ -114,7 +114,14 @@ static void power_down(uint8_t wdto) {
 #endif
 
   // Turn off LED indicators
-	led_set(0);
+  uint8_t leds_off = 0;
+#if defined(BACKLIGHT_CAPS_LOCK) && defined(BACKLIGHT_ENABLE)
+  if (is_backlight_enabled()) {
+    // Don't try to turn off Caps Lock indicator as it is backlight and backlight is already off
+    leds_off |= (1<<USB_LED_CAPS_LOCK);
+  }
+#endif
+  led_set(leds_off);
 
 #ifdef AUDIO_ENABLE
   // This sometimes disables the start-up noise, so it's been disabled