Arduino has determined that a limited number of Arduino Nano ESP32 boards were assembled with an RGB LED which has the green and blue pins inverted.

The inverted pins will result in the following behavior:

• The predefined LED_GREEN constant will have the blue LED pin number.
• The predefined LED_BLUE constant will have the green LED pin number.
• The RGB LED will be blue instead of green when the board is in recovery mode.
• The RGB LED will be yellow instead of purple when the board is in bootloader mode.

Identify which RGB LED is on your board

It is possible to determine the type of RGB LED by visually inspecting the board:

1. Find the white reset button on the top of the board.
2. Hold the board so that the USB port is facing upward, and the RST label facing the right way.
3. Locate the RGB LED just right of the reset button.
4. Look closely at the RGB LED component:
   • If it has a black color, it does not have swapped green and blue pins.
   • If it has a gray/green color, it has swapped green and blue pins.

Using the RGB LED with inverted green and blue pins

Referencing the pins directly

When writing to the RGB LED pins, use 16 for green, and 15 for blue.

Set the RGB LED to green:

digitalWrite(14, HIGH); // Red OFF
digitalWrite(16, LOW);  // Green ON
digitalWrite(15, HIGH); // Blue OFF

Set the RGB LED to blue:

digitalWrite(14, HIGH); // Red OFF
digitalWrite(16, HIGH); // Green OFF
digitalWrite(15, LOW);  // Blue ON

Declaring your own constants

For convenience, you can declare your own constants in sketches where you use the RGB LED:

const uint8_t MY_LED_RED   = 14;
const uint8_t MY_LED_GREEN = 16;
const uint8_t MY_LED_BLUE  = 15;

Set the RGB LED to purple with the above constants:

digitalWrite(MY_LED_RED, LOW); // Red ON
digitalWrite(MY_LED_GREEN, HIGH); // Green OFF
digitalWrite(MY_LED_BLUE, LOW);  // Blue ON

Correcting the predefined constants by editing io_pin_remap.cpp

If you’re comfortable editing files inside the board core, you can change a few lines so that the LED_GREEN and LED_BLUE constants have the correct values.

Follow these steps:

1. Open the Arduino 15 folder^(?).

2. Navigate to packages/arduino/hardware/esp32/<version>.

3. Open io_pin_remap.cpp in a text editor.

4. Find the following lines:

   [LED_RED]   = 46,
   [LED_GREEN] = 0,
   [LED_BLUE]  = 45, // RTS
   

5. Edit them so they look like this:

   [LED_RED]   = 46,
   [LED_GREEN] = 45, // RTS
   [LED_BLUE]  = 0,
   

6. Save the changes to io_pin_remap.cpp.

To preserve hardware flow control on the serial port, also make this change in pins_arduino.h:

1. Inside the same folder as before, open pins_arduino.h.

2. Find the line

   static constexpr uint8_t RTS  = LED_BLUE;
   

   and change it to

   static constexpr uint8_t RTS  = LED_GREEN;
   

3. Save the changes to pins_arduino.h.

Note that the changes will be overwritten if you update or change the esp32 board package version.