digitalWrite(LED_BUILTIN, LOW); turns on the led

@kaffemitmilf, your topic has been moved to a more suitable location on the forum. Installation and Troubleshooting is not for problems with (nor for advise on) your project :wink: See About the Installation & Troubleshooting category.

A LED (plus resistor) can be wired to a microcontroller in two ways

  1. between pin and GND in which case you have to drive the pin HIGH to switch the LED on.
  2. between pin and Vcc in which case you have to drive the pin LOW to switch the LED on.
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