According to this guide, only the following pins are available for my use:

2, 3, 4, 7, 8, 9, 10, 11, 14, 15, 17, 18, 22, 23, 24, 25, 27, with 28, 29, 30, 31

So that's 17 pins and then 4 on the header.

Now when I look at the pin-out for the model B+ board:

enter image description here

I see GPIO pins GPIO05, GPIO06, GPIO12, GPIO13, GPIO16, GPIO19, GPIO20, GPIO21 and GPIO26 are shown. Why can't I use these?

They are also listed here.

I am using a RPi Version 2 which I understand uses the same form-factor as B+ and need to know which pins I can use and which I can't. I just don't understand which pins I can and cannot use and if the above is correct, why I can't use them.

  • THe first link appears to apple to model A and B, the picture above and the second link are model B+ and it has more GPIO pins. Use em! – Tyson Feb 13 '15 at 16:03
  • You can use them if you want. However the gpios are not connected to the outside world via pins on the Pi B Rev. 2 so they will be of limited use. – joan Feb 13 '15 at 16:26
  • So in summary, those pins are fine for me to use on the B+ board with the 40 pin header? – Neil Trodden Feb 13 '15 at 16:33
  • All gpios brought out to the expansion header are fine to use. – joan Feb 13 '15 at 16:41
  • How are you trying to use them? Are you trying to use them from Python using the RPi.GPIO library? If so, there is currently a bug which prevents those pins from being used. A fix is in progress and should be available in the next week using apt-get update/upgrade – recantha Feb 13 '15 at 19:16

I too was confused when I saw the Raspberry Pi documentation that said I could not use GPIO05, GPIO06, GPIO12, GPIO13, GPIO16, GPIO19, GPIO20, GPIO21, and GPIO26. I believe this is simply a holdover from the days when the Raspberry Pi's header did not yet have the extra 6 rows.

I have a Raspberry Pi 3 Model B V1.2 and I am able to use GPIO20 as expected.

A simple sysfs gpio example:

sudo -i # Usually, sysfs gpio access is restricted to root. Raspbian seems to have an extra gpio group that can be used.
cd /sys/class/gpio
echo 20 > export
cd gpio20
echo out > direction
echo 1 > value

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