add mandatory build flags for -S2 and -C3 (virtual USB)

I was wondering why sometimes the new MCUs still work better in Arduino IDE, so compared our build flags to what is used in Arduino IDE:

-S2 always has -DARDUINO_USB_MODE=0
-C3 always has -DARDUINO_USB_MODE=1
-S3 supports all possible modes

platformio.ini

@@ -214,6 +214,7 @@ build_flags = -g
   -D CONFIG_ASYNC_TCP_USE_WDT=0
 #use LITTLEFS library by lorol in ESP32 core 1.x.x instead of built-in in 2.x.x
   -D LOROL_LITTLEFS
+  ; -DARDUINO_USB_CDC_ON_BOOT=0 ;; this flag is mandatory for "classic ESP32" when builing with arduino-esp32 >=2.0.3
 
 default_partitions = tools/WLED_ESP32_4MB_1MB_FS.csv
 
@@ -230,6 +231,9 @@ build_flags = -g
   -DCONFIG_IDF_TARGET_ESP32S2
   -D CONFIG_ASYNC_TCP_USE_WDT=0
   -DCO
+  -DARDUINO_USB_MODE=0 ;; this flag is mandatory for ESP32-S2 !
+  ;; please make sure that the following flags are properly set (to 0 or 1) by your board.json, or included in your custom platformio_override.ini entry:
+  ;; ARDUINO_USB_CDC_ON_BOOT, ARDUINO_USB_MSC_ON_BOOT, ARDUINO_USB_DFU_ON_BOOT
 
 lib_deps =
   ${env.lib_deps}
@@ -243,6 +247,9 @@ build_flags = -g
   -DCONFIG_IDF_TARGET_ESP32C3
   -D CONFIG_ASYNC_TCP_USE_WDT=0
   -DCO
+  -DARDUINO_USB_MODE=1 ;; this flag is mandatory for ESP32-C3
+  ;; please make sure that the following flags are properly set (to 0 or 1) by your board.json, or included in your custom platformio_override.ini entry:
+  ;; ARDUINO_USB_CDC_ON_BOOT
 
 lib_deps =
   ${env.lib_deps}
@@ -258,6 +265,8 @@ build_flags = -g
   -DCONFIG_IDF_TARGET_ESP32S3
   -D CONFIG_ASYNC_TCP_USE_WDT=0
   -DCO
+  ;; please make sure that the following flags are properly set (to 0 or 1) by your board.json, or included in your custom platformio_override.ini entry:
+  ;; ARDUINO_USB_MODE, ARDUINO_USB_CDC_ON_BOOT, ARDUINO_USB_MSC_ON_BOOT, ARDUINO_USB_DFU_ON_BOOT
 
 lib_deps =
   ${env.lib_deps}
@@ -387,6 +396,7 @@ board = esp32-c3-devkitm-1
 board_build.partitions = tools/WLED_ESP32_4MB_1MB_FS.csv
 build_flags = ${common.build_flags} ${esp32c3.build_flags} #-D WLED_RELEASE_NAME=ESP32-C3
   -D WLED_WATCHDOG_TIMEOUT=0
+  ; -DARDUINO_USB_CDC_ON_BOOT=1 ;; for virtual USB
 upload_speed = 460800
 build_unflags = ${common.build_unflags}
 lib_deps = ${esp32c3.lib_deps}

wled00/wled.cpp

@@ -268,7 +268,10 @@ void WLED::setup()
   #endif
 
   Serial.begin(115200);
-  Serial.setTimeout(50);
+  #if !ARDUINO_USB_CDC_ON_BOOT
+  Serial.setTimeout(50);  // this causes troubles on new MCUs that have a "virtual" USB Serial (HWCDC)
+  #else
+  #endif
   #if defined(WLED_DEBUG) && defined(ARDUINO_ARCH_ESP32) && (defined(CONFIG_IDF_TARGET_ESP32S2) || defined(CONFIG_IDF_TARGET_ESP32C3) || ARDUINO_USB_CDC_ON_BOOT)
   delay(2500);  // allow CDC USB serial to initialise
   #endif

wled00/wled.h

@@ -71,6 +71,7 @@
   #include <user_interface.h>
   }
 #else // ESP32
+  #include <HardwareSerial.h>  // ensure we have the correct "Serial" on new MCUs (depends on ARDUINO_USB_MODE and ARDUINO_USB_CDC_ON_BOOT)
   #include <WiFi.h>
   #include <ETH.h>
   #include "esp_wifi.h"