Gemma does not define LED_BUILTIN

[matthijskooijman]

But AFAIU, it does have a built in led.

[pwillard]

Locate your IDE program installation folder, and under \hardware\arduino\avr\variants\gemma edit "pins_arduino.h". In the file, under your pin constants for A0 - A3, add the following line:

#define LED_BUILTIN 1

Save the file and start the IDE.

And yes... Adafruit should have done this... for shame.

[agdl]

Done thank you!

[pwillard]

FYI: Adafruit Trinket needs the same love...