On my Raspberry Pi, I tried to do some experiments with GPIO, without success.

Measuring the voltage between GND and GPIO11, for example, always helds a result of 0. I am using /sys/class/gpio commands to turn GPIO on and off. Between GND and 3.3V, it returns 2.2V. Te only one that seems to work is between GND and 5v.


Any clues?

Am I doing something wrong?

  • 1
    If you told us what you have actually done you may get some help
    – Milliways
    Dec 21, 2013 at 4:09

1 Answer 1


If you followed the instructions, this should work. I suspect that you have your cable crossed over. You say Measured P1-25 (GND) and P1-01 (3v3). Got 2.2 V This is wrong, I suspect that you are actually measuring between pin 2 (5v) and pin 26.

I suggest you install WiringPi (mentioned in the instructions). This is much easier to use, and more importantly includes a utility gpio readall which displays the state of all the pins.

Get your instructions right (as shown in the gpio readall utility) then you can work out if you have a wiring problem. NOTE this works even if nothing is connected.

  • You saved my life! My cable was indeed crossed over. There was an arrow on the cable that was supposed to point at P1 on Raspberry. Dec 22, 2013 at 15:18

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.