I have noted in previous questions and I understand the PWM area of the raspberry pi is the most saturated area, but my question lies in which ports can actually be allocated as a PWM output due to DMA.

enter image description here (Sourced: https://www.modmypi.com/blog/raspberry-pi-gpio-en-franais)

I don't wish to damage my board, but from the above diagram other than the ports 18 and 21 which ports can I actually specify to output as a software PWM instead, without risking any damage. This question is more of me trying to be cautious of what I'm doing.

Please forgive me as I'm still learning and any direction that I can be pointed in will be good.

1 Answer 1


It is safe to use PWM (however you generate the pulses) on any gpio on the expansion header.

For a model B:

For a Rev.1 board gpios 0-1, 4, 7-11, 14-15, 17-18, 21-25.

For a Rev.2 board gpios 2-4, 7-11, 14-15, 17-18, 22-25, 27-31.

For a Rev.3 board gpios 2-27.
  • Alright ill look up the rev number, it seems you are the guardian Angel of pwm lol thanks man, just better to be safe than sorry.
    – Pariah
    Sep 5, 2014 at 8:05
  • 1
    It's probably easiest to look for "mounting holes" on the board, None is Rev.1, 2 is Rev.2, 4 is Rev.3.
    – joan
    Sep 5, 2014 at 8:40
  • Fair enough, well im on my way back from work to check my board, because this is something that has been bothering me.
    – Pariah
    Sep 5, 2014 at 8:45
  • 1
    That means it's Rev.2 in my terms (gpios 2-4, 7-11, 14-15, 17-18, 22-25, 27-31 on the expansion headers).
    – joan
    Sep 5, 2014 at 11:34
  • 1
    Yes, they should be about 2.4mm in diameter I think. Yours should have two.
    – joan
    Sep 5, 2014 at 11:36

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