In the pic, I have connected GPIO 17 to resistor, which connects to an led which connects to the ground. The rasberry pi is connected to the board via the ribbon. I have not explicitly connected the power pins 2,4 to the GPIO, resistor, LED circuit. How is the circuit getting power?

enter image description here

1 Answer 1


It will get power from the power supply you have plugged in to the Pi.

As long as the Pi is powered 3V3 will be supplied to pins 1 and 17 and 5V will be supplied to pins 2 and 4.

The GPIO will also receive power from the 3V3 supply. Each GPIO also has internal pulls. Some GPIO default to pulls to 3V3, others default to pulls to ground.

GPIO 17 default to pull low. If it is lit this suggests the other end of the circuit is connected to 3V3. If that's not the case then you must have set GPIO 17 as a high output.

  • Thanks. I suppose you mean that 3V3 will be supplied to physical pin 17. GPIO 17 maps to physical pin 11. Commented Apr 1, 2021 at 16:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.