Python daemon to watch a GPIO pin and trigger a clean shutdown.
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README.md

clean-shutdown

clean-shutdown is a simple daemon that monitors a user-specified GPIO pin and triggers a clean software shutdown when that pin is asserted low. It offers ways to customise the behaviour of the shutdown process to fit most use-cases.

Installation

The setup.sh script provided in this repository can be used to set your preference of GPIO pin to monitor in order to initiate the shutdown. To install support for a specific product however, such as OnOff SHIM or Zero LiPo, we recommend you use the one-line installers listed further down the page.

We highly recommend you use the generic one-line installer rather than run the setup.sh script directly, like so:

curl https://get.pimoroni.com/cleanshutdown | bash

If you need to however, for example because the above command states that your operating system is not supported, clone this repository locally and run setup.sh. When prompted, enter the pin you would you like to use as trigger for the shutdown.

Note that the setup script expects an integer value between 4 and 27 (you can use others outside this range by manually editing the config file as explained below, but there are caveats so if it does not quite work, you're on your own!)

Supported Products

In addition to the generic install described above, where you get to choose your preferred custom trigger pin, the following specific products are supported:

  • OnOff SHIM - Uses BCM 17 as trigger and LED pin, and BCM 4 as the power off pin; argument to pass: onoffshim
  • Zero LiPo / LiPo SHIM - Uses BCM 4 as the power off pin; argument to pass: zerolipo

You may pass the setup.sh the product as an argument, as detailed above. HOWEVER, again, we recommend that you use our one-line installers, which are better equipped to handle some specific distributions idiosyncracies.

OnOff SHIM

If you are using a OnOff SHIM, you should use our dedicated one-line installer, which will ensure the daemon configuration is optimal for that product:

curl https://get.pimoroni.com/onoffshim | bash

Zero LiPo / LiPo SHIM

If you are using a Zero LiPo / LiPo SHIM, you should use our dedicated one-line installer, which will ensure the daemon configuration is optimal for that product:

curl https://get.pimoroni.com/zerolipo | bash

Usage

There is really not a lot that needs to be done once the daemon is in place - which will be the case after installation and reboot... this is all very straightforward!

That said, clean-shutdown has some interesting features that your particular use-case may require. For example, if you are using an input trigger you would normally expect the shutdown to occur as soon as you press the control. But what if that is not what you want?

clean-shutdown provides several useful parameters to adapt the shutdown behaviour or exact monitoring environment to your project, without requiring you to mess with the daemon code, or understand what it does in the finer details.

If you find yourself in such a need, fire up your favourite editor and open /etc/cleanshutd.conf. The parameters documented below can then be customised as desired.

Note that in order for parameters changes to take effect the deamon has to be restarted. The easier way to do that is to reboot the Pi, or run:

sudo service cleanshutd restart

Parameters

daemon_active

This is a pretty hacky way to passify the daemon without needing to delve into the details of systemd. Set to 0 to deactivate the daemon (technically the daemon will be started at boot time but it will do absolutely nothing). Set to 1 to reactivate.

trigger_pin

Normally you'll set this up at install time and won't need to change it, but... as we do, next week you might buy a nice shiny (Pimoroni) HAT or pHAT and find that the pin you had your clean shutdown trigger wired to is required by your new friend. Just move the trigger button to another pin and reboot! The unit used for this parameter is the bcm number for the pin (4 or above recommended, 0-3 have particularities that make them slightly less straightforward to use, though the daemon will happily monitor them for you, so as long as you know what you're doing go right ahead).

led_pin

This parameter determines a pin can be pulled low to blink a status LED, first showing that shutdown has been armed, and finally blinking three times to show that final power off is imminent. So feel free to wire a LED onto a GPIO pin and set the parameter accordingly if you like.

poweroff_pin

For products that support it (eg: OnOff SHIM), the poweroff_pin determines which pin will be pulled low right at the end of your Pi's shutdown process. If supported, this will cause power to your Pi to be cut completely.

hold_time

This parameter determines the amount of time you must hold down the button until shutdown occurs. It defaults to 1 second to avoid accidental shutdowns. The unit for hold_time is expressed in seconds. Use 0 to shutdown as soon as the button is pressed.

shutdown_delay

Most of the time you probably want your Pi to shutdown as soon as the trigger occurs, but sometimmes, like with the Zero Lipo, once the battery warning has been detected you still got some life of the LiPo before it is necessary to shut it down (the 'battery low' warning is activated at 3.4V, but the protection circuitry will only cut off the supply at 3.0V). The unit for shutdown_delay is expressed in minutes (0, the default, means immediate shutdown).

polling_rate

This parameter determines how often the trigger is checked for. Normally, a small but reasonable value, say a second or 2 is adequate to detect a button press without polling constantly, but if you take the Zero Lipo example again it really does not matter if the monitoring is more relaxed, say if polling is performed every 30 seconds or so. There may be other use-cases where smaller or larger values are optimal, so there's a parameter for the occasion if you find yourself in one. Units for polling_rate are expressed in seconds.

Parasitic Shutdowns

Be aware that altering the state of trigger_pin can throw you in a scenario where your Pi shuts down right away upon boot, if a process, dtoverlay, or HAT EEPROM, just to name a few possibilities, pulls it low on boot (or set it as an output, which implies it being driven low initially).

If this occurs right after you plugged a HAT, then try booting without it attached, and disable the cleatshutd service with:

sudo systemctl disable cleanshutd

There is another way, which is provided as an emergency solution for scenarios where reaching the bash prompt is not possible (because the Pi shuts down before you get a chance to do so).

In such cases, or as an alternative to the above, you may add the following to your /boot/config.txt file from another computer:

disable_cleanshutd=1