What If My LED Doesn't Blink?

If you're using an ESP8266 12E with NodeMCU, then 0 corresponds to GPIO0, which is pin D3. You can bridge an LED to ground to verify blinking. The on-board LED's on some versions (I'm using a 12e) are connected to the TX/RX UART pins, so if you program them to drive the LED, you'll not be able to upload your sketches without holding down the flash button, which is slightly inconvenient. If you get advanced and need the pin, it's there for you, though.

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bekathwia1 month ago

Thanks for posting that info! One of the reasons I encourage students to use the Adafruit Feather Huzzah board is little pinout stuff like that. The NodeMCU board is widely available but a bit trickier to use (and because multiple suppliers are selling them, manufacturing quality can be a bit inconsistent, for instance mine has a flaky USB port)