✨ RGB_STARTUP_TEST

Marlin/Configuration.h

  * luminance values can be set from 0 to 255.
  * For NeoPixel LED an overall brightness parameter is also available.
  *
- * *** CAUTION ***
+ *  === CAUTION ===
  *  LED Strips require a MOSFET Chip between PWM lines and LEDs,
  *  as the Arduino cannot handle the current the LEDs will require.
  *  Failure to follow this precaution can destroy your Arduino!
+ *
  *  NOTE: A separate 5V power supply is required! The NeoPixel LED needs
  *  more current than the Arduino 5V linear regulator can produce.
- * *** CAUTION ***
  *
- * LED Type. Enable only one of the following two options.
+ *  Requires PWM frequency between 50 <> 100Hz (Check HAL or variant)
+ *  Use FAST_PWM_FAN, if possible, to reduce fan noise.
  */
+
+// LED Type. Enable only one of the following two options:
 //#define RGB_LED
 //#define RGBW_LED
 
   //#define RGB_LED_G_PIN 43
   //#define RGB_LED_B_PIN 35
   //#define RGB_LED_W_PIN -1
+  //#define RGB_STARTUP_TEST              // For PWM pins, fade between all colors
+  #if ENABLED(RGB_STARTUP_TEST)
+    #define RGB_STARTUP_TEST_INNER_MS 10  // (ms) Reduce or increase fading speed
+  #endif
 #endif
 
 // Support for Adafruit NeoPixel LED driver

Marlin/src/feature/leds/leds.cpp

     #if ENABLED(RGBW_LED)
       if (PWM_PIN(RGB_LED_W_PIN)) SET_PWM(RGB_LED_W_PIN); else SET_OUTPUT(RGB_LED_W_PIN);
     #endif
+
+    #if ENABLED(RGB_STARTUP_TEST)
+      int8_t led_pin_count = 0;
+      if (PWM_PIN(RGB_LED_R_PIN) && PWM_PIN(RGB_LED_G_PIN) && PWM_PIN(RGB_LED_B_PIN)) led_pin_count = 3;
+      #if ENABLED(RGBW_LED)
+        if (PWM_PIN(RGB_LED_W_PIN) && led_pin_count) led_pin_count++;
+      #endif
+      // Startup animation
+      if (led_pin_count) {
+        // blackout
+        if (PWM_PIN(RGB_LED_R_PIN)) hal.set_pwm_duty(pin_t(RGB_LED_R_PIN), 0); else WRITE(RGB_LED_R_PIN, LOW);
+        if (PWM_PIN(RGB_LED_G_PIN)) hal.set_pwm_duty(pin_t(RGB_LED_G_PIN), 0); else WRITE(RGB_LED_G_PIN, LOW);
+        if (PWM_PIN(RGB_LED_B_PIN)) hal.set_pwm_duty(pin_t(RGB_LED_B_PIN), 0); else WRITE(RGB_LED_B_PIN, LOW);
+        #if ENABLED(RGBW_LED)
+          if (PWM_PIN(RGB_LED_W_PIN)) hal.set_pwm_duty(pin_t(RGB_LED_W_PIN), 0);
+          else WRITE(RGB_LED_W_PIN, LOW);
+        #endif
+        delay(200);
+
+        LOOP_L_N(i, led_pin_count) {
+          LOOP_LE_N(b, 200) {
+            const uint16_t led_pwm = b <= 100 ? b : 200 - b;
+            if (i == 0 && PWM_PIN(RGB_LED_R_PIN)) hal.set_pwm_duty(pin_t(RGB_LED_R_PIN), led_pwm); else WRITE(RGB_LED_R_PIN, b < 100 ? HIGH : LOW);
+            if (i == 1 && PWM_PIN(RGB_LED_G_PIN)) hal.set_pwm_duty(pin_t(RGB_LED_G_PIN), led_pwm); else WRITE(RGB_LED_G_PIN, b < 100 ? HIGH : LOW);
+            if (i == 2 && PWM_PIN(RGB_LED_B_PIN)) hal.set_pwm_duty(pin_t(RGB_LED_B_PIN), led_pwm); else WRITE(RGB_LED_B_PIN, b < 100 ? HIGH : LOW);
+            #if ENABLED(RGBW_LED)
+              if (i == 3){
+                if (PWM_PIN(RGB_LED_W_PIN)) hal.set_pwm_duty(pin_t(RGB_LED_W_PIN), led_pwm);
+                else WRITE(RGB_LED_W_PIN, b < 100 ? HIGH : LOW);
+                delay(RGB_STARTUP_TEST_INNER_MS);//More slowing for ending
+              }
+            #endif
+            delay(RGB_STARTUP_TEST_INNER_MS);
+          }
+        }
+        delay(500);
+      }
+    #endif // RGB_STARTUP_TEST
   #endif
   TERN_(NEOPIXEL_LED, neo.init());
   TERN_(PCA9533, PCA9533_init());