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I am running Ubuntu Mate on a Raspberry Pi 2B.

I would like to find which GPIO pin is currently used for the heartbeat, i.e. activity, so I can attach an external LED.

The config.txt entry is like so:

## act_led_gpio
##     Set which GPIO to use for the activity LED
##
##     In case you want to connect it to an external device
##     
##     Default 16 on a non-Plus board, 47 on a Plus or Pi 2.
##
#dtparam=act_led_gpio=47

There are only forty pins, so it can't be physical pin 47, or the GPIO BCM numbering. Does anyone know which system is used here?

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It is BCM and 47 is only internal and control the activity LED. All GPIO isn't populated out to the 2x20 pin header.

To use an external LED just redefine dtparam=act_led_gpio=47 to something of your liking, example:

dtparam=act_led_gpio=23

And place a LED on pin 16 (GPIO23) with appropriate resistor.

PS. and remove the # in the beginning.

  • #Yes I will, wouldn't work great otherwise! Just a question, will setting it to anything else disable the inbuilt act LED? – hat Jan 15 '18 at 16:58
  • Well not anything, but yes you redirect dtparam=act_led_gpio from default 47 to another destination, like 23 in my example. But to use a random number isn't recommended, you could get a conflict! – MatsK Jan 15 '18 at 17:06
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    Sorry, I could have said it more clearly, I was asking if changing the pin would disable the act LED on the board. – hat Jan 15 '18 at 17:11
  • Yes it does. You are telling the the Raspberry to NOT use 47 and to use another one instead. – MatsK Jan 15 '18 at 17:16

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