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Merge pull request #242 from waveform80/built-in-leds

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Fix #148
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Dave Jones
2016-04-01 23:15:08 +01:00
parent af94fc2aac 6b2e014975
commit a59f8f6b35
1 changed files with 47 additions and 0 deletions
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docs/recipes.rst
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@@ -709,6 +709,53 @@ Please note the example above requires Python 3. In Python 2, :func:`zip`
doesn't support lazy evaluation so the script will simply hang.
Controlling the Pi's own LEDs
=============================
On certain models of Pi (specifically the model A+, B+, and 2B) it's possible
to control the power and activity LEDs. This can be useful for testing GPIO
functionality without the need to wire up your own LEDs (also useful because
the power and activity LEDs are "known good").
Firstly you need to disable the usual triggers for the built-in LEDs. This can
be done from the terminal with the following commands::
$ echo none | sudo tee /sys/class/leds/led0/trigger
$ echo gpio | sudo tee /sys/class/leds/led1/trigger
Now you can control the LEDs with gpiozero like so::
from gpiozero import LED
from signal import pause
power = LED(35)
activity = LED(47)
activity.blink()
power.blink()
pause()
To revert the LEDs to their usual purpose you can either reboot your Pi or
run the following commands::
$ echo mmc0 | sudo tee /sys/class/leds/led0/trigger
$ echo input | sudo tee /sys/class/leds/led1/trigger
.. note::
On the Pi Zero you can control the activity LED with this recipe, but
there's no separate power LED to control (it's also worth noting the
activity LED is active low, so set ``active_high=False`` when constructing
your LED component.
On the original Pi 1 (model A or B), the activity LED can be controlled
with GPIO16 (after disabling its trigger as above) but the power LED is
hard-wired on.
On the Pi 3B the LEDs are controlled by a GPIO expander which is not
accessible from gpiozero (yet).
.. _Push Button Stop Motion: https://www.raspberrypi.org/learning/quick-reaction-game/
.. _Quick Reaction Game: https://www.raspberrypi.org/learning/quick-reaction-game/
.. _GPIO Music Box: https://www.raspberrypi.org/learning/gpio-music-box/