I have 8 RGB LEDs in a Row. Each RGB LED has 3 GPIO pin to control the color Red Green and Blue. I used all available GPIO pins. I works for the 7 RGB LEDs. One LEDs does not light properly for 2 colors. I check the GPIO Pin and it's the 9th and the 10th. It's written MOSI and MISO as well. I don't know if that's related to the problem. enter image description here

Why those two pins cannot light the LED?

1 Answer 1


All the GPIO on the expansion header can be set as INPUTS and OUTPUTS. When set as an OUTPUT each GPIO may be driven high and low.

There are several possibilities.

  1. You haven't connected the LED to GPIO 9/10 properly.
  2. The software you are using is incorrect.
  3. Your Pi is broken.

To eliminate 1 and 2 you would have to provide a photo of the connections you have made and a listing of the software.

To eliminate 3 try gpiotest.

  • It was the big resistor on the breadboard that connected the pin Green and Blue. => Short circuit
    – TSR
    Commented Aug 14, 2017 at 12:10

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