bugfix - unusable pins on pico32 boards (#3573)

According to the technical manual, GPIO 16 + 17 are used for onboard flash, so cannot be used by WLED.

example buildenv:

[env:esp32_pico]
extends = env:esp32dev_qio80
board = pico32

wled00/const.h

@@ -460,8 +460,8 @@
 
 //this is merely a default now and can be changed at runtime
 #ifndef LEDPIN
-#if defined(ESP8266) || (defined(ARDUINO_ARCH_ESP32) && defined(WLED_USE_PSRAM)) || defined(CONFIG_IDF_TARGET_ESP32C3)
-  #define LEDPIN 2    // GPIO2 (D4) on Wemos D1 mini compatible boards
+#if defined(ESP8266) || (defined(ARDUINO_ARCH_ESP32) && defined(WLED_USE_PSRAM)) || defined(CONFIG_IDF_TARGET_ESP32C3) || defined(ARDUINO_ESP32_PICO)
+  #define LEDPIN 2    // GPIO2 (D4) on Wemos D1 mini compatible boards, and on boards where GPIO16 is not available
 #else
   #define LEDPIN 16   // aligns with GPIO2 (D4) on Wemos D1 mini32 compatible boards
 #endif

wled00/wled.cpp

@@ -374,6 +374,11 @@ void WLED::setup()
   #else
     DEBUG_PRINTLN(F("PSRAM not used."));
   #endif
+#endif
+#if defined(ARDUINO_ESP32_PICO)
+// special handling for PICO-D4: gpio16+17 are in use for onboard SPI FLASH (not PSRAM)
+managed_pin_type pins[] = { {16, true}, {17, true} };
+pinManager.allocateMultiplePins(pins, sizeof(pins)/sizeof(managed_pin_type), PinOwner::SPI_RAM);
 #endif
 
   //DEBUG_PRINT(F("LEDs inited. heap usage ~"));