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geerlingguy
Posts: 32
Joined: Sun Feb 15, 2015 3:43 am
Location: St. Louis, MO, USA
Contact: Website

Disable ACT LED on Pi Zero

Sun Nov 29, 2015 3:46 am

I've tried controlling led0 and led1 on the Pi Zero (using the OS install of the official Raspbian Jessie Lite image, Nov/2015), and it seems none of the controls do anything for the single LED (labeled ACT) on the Pi Zero. I was using the instructions, basically, from this post: http://www.midwesternmac.com/blogs/jeff ... wr-and-act

Does anyone know if it will be possible to control that LED and either switch what it's set to indicate (it seems to indicate disk access by default) or disable it by setting 'brightness' to '0'?
My personal site: http://jeffgeerling.com/

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rpdom
Posts: 11522
Joined: Sun May 06, 2012 5:17 am
Location: Essex, UK

Re: Disable ACT LED on Pi Zero

Sun Nov 29, 2015 9:13 am

I haven't got a zero, so I can't test this, but it might be possible to redefine the ACT LED function using device tree parameters in config.txt

Code: Select all

dtparam=act_led_trigger=none
Or perhaps, as the LED seems to be inverted like the original Pi A/B (fewer components required), either

Code: Select all

dtparam=act_led_trigger=default-on
or

Code: Select all

dtparam=act_led_trigger=none
dtparam=act_led_activelow=on

User avatar
geerlingguy
Posts: 32
Joined: Sun Feb 15, 2015 3:43 am
Location: St. Louis, MO, USA
Contact: Website

Re: Disable ACT LED on Pi Zero

Mon Nov 30, 2015 2:24 am

rpdom wrote:

Code: Select all

dtparam=act_led_trigger=none
dtparam=act_led_activelow=on
This worked perfectly! I've updated the blog post linked in the first comment, and here are the commands to temporarily disable the LED (it's opposite, as you predicted):

Code: Select all

# Set the Pi Zero ACT LED trigger to 'none'.
echo none | sudo tee /sys/class/leds/led0/trigger

# Turn off the Pi Zero ACT LED.
echo 1 | sudo tee /sys/class/leds/led0/brightness
My personal site: http://jeffgeerling.com/

pitchlynn
Posts: 16
Joined: Sun Oct 23, 2016 9:11 pm

Re: Disable ACT LED on Pi Zero

Tue Nov 08, 2016 12:13 am

I am using this is in my python script to control the act LED but I'm finding it takes too long to execute so I'm missing input signals.

Both of these lines of code takes 0.12 seconds to execute.
Turn ACT LED on:

Code: Select all

echo 1 | sudo tee /sys/class/leds/led0/brightness
 
Trun Act LED off:

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echo 0 | sudo tee /sys/class/leds/led0/brightness
 
Am I using this wrong by placing it directly in my script?

Maybe it would help if I understood it more if someone could break down that one line of code.

simon3270
Posts: 2
Joined: Mon Jan 09, 2017 3:34 pm

Re: Disable ACT LED on Pi Zero

Tue Jan 10, 2017 12:21 pm

The problem is that you are loading up a shell, and a sudo command, and a tee command, just to write a single character to a file.

You can do this directly from your Python script, but you do need to be root to do it. If you are happy to run your entire script as root, just do something like this to turn it off (and write '0\n' to turn it on):

Code: Select all

with open("/sys/class/leds/led0/brightness","w") as f:
     f.write('1\n')

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