Commit 0f9f9585 authored by David Boddie's avatar David Boddie 💬
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Add more information about the brightness limitations

parent e3fa6a15
......@@ -7,18 +7,22 @@ The Librem 5 has a number of peripherals that allow applications to interact
with users and the outside world in a simple way. This guide covers these I/O
peripherals and describes how to use them.
LEDs
----
Light Emitting Diodes (LEDs)
----------------------------
Only one of the light-emitting diodes (LEDs) can be controlled by
applications. This red diode is mapped to the ``/sys/class/leds/LED 1``
directory in the file system and its state can be changed by writing
to the ``/sys/class/leds/LED 1/brightness`` file, like this shell command::
Only one of the LEDs can be controlled by applications. This red diode is
mapped to the ``/sys/class/leds/LED 1`` directory in the file system and its
state can be changed by writing to the ``/sys/class/leds/LED 1/brightness``
file, as in this shell command::
echo 200 > /sys/class/leds/LED\ 1/brightness
Using the default system configuration, writing a value of 0 to the file will
switch the LED off. Writing a value from 1 to 255 will switch it on. If a
different device tree is used with the kernel, this behavior can be adjusted.
switch the LED off. Writing a value from 1 to 255 will switch it on.
The lack of control over the brightness of the LED is because it is driven by
a Pulse Width Modulator (PWM) that it shares with the haptic motor, and the
default kernel device tree configures the motor to use the PWM. If a different
device tree is used with the kernel, this behavior can be adjusted.
.. Perhaps link to issue https://source.puri.sm/Librem5/developer.puri.sm/issues/68
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