Posts by MikeF

MikeF · [How to] Pimoroni OnOff SHIM with LibreELEC MikeF April 30, 2020 at 1:17 PM

I have been able to install the Pimoroni OnOff SHIM on my RPi running LibreELEC. The OnOff SHIM enables you to completely power off - and power on again - a Raspberry Pi with a single pushbutton. As mentioned elsewhere in this forum, it is not possible to install it using Pimoroni's install script, as this requires use of apt-get to install packages, which is not available under LibreELEC; also, it would be necessary to change paths throughout the script.

I came across this thread on the Retropie forum, where the author had stripped this down to two simple shell scripts. Inspired by this, I have created the following scripts for LibreELEC.

The first is a python script, which checks for the button being pressed, and if held for > 1 second (as with the Pimoroni script), invokes the halt (or poweroff) os command. This requires the Raspberry Pi Tools add-on, and should be called from autostart.sh. (I saved it in /storage/.kodi/userdata.)

Python

#!/usr/bin/env python

from time import sleep
import sys, os
sys.path.append("/storage/.kodi/addons/virtual.rpi-tools/lib")
import RPi.GPIO as GPIO

pin = 17 

GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)

def button_action(pin):
    button_press_timer = 0
    while True:
        if (GPIO.input(pin) == False) : # while button is still pressed down
            button_press_timer += 1 # keep counting until button is released
        else: # button is released, figure out for how long
            if (button_press_timer > 1) : # pressed for > 1 second
                os.system("halt")
            button_press_timer = 0
        sleep(1)

GPIO.add_event_detect(pin, GPIO.FALLING, callback=button_action, bouncetime=20)

try:
    while True:
        sleep(0.5)
except KeyboardInterrupt:
        GPIO.cleanup()       # clean up GPIO on CTRL+C exit

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The second script, which is called as part of the shutdown process, will flash the SHIM's onboard LED 3 times, and then drive GPIO 4 low, cutting the power to the RPi (as with the Pimoroni script):

Bash

#!/bin/sh
#

if [ "$1" != "reboot" ]; then

    poweroff_pin="4"    
    led_pin="17"
    trigger_pin="17"    

    echo $trigger_pin > /sys/class/gpio/export

    echo out > /sys/class/gpio/gpio$led_pin/direction    

    for iteration in 1 2 3; do    
        echo 0 > /sys/class/gpio/gpio$led_pin/value    
        sleep 0.2    
        echo 1 > /sys/class/gpio/gpio$led_pin/value    
        sleep 0.2    
    done    

    echo $poweroff_pin > /sys/class/gpio/export    
    echo out > /sys/class/gpio/gpio$poweroff_pin/direction    
    echo 0 > /sys/class/gpio/gpio$poweroff_pin/value

fi

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This needs to be saved as /storage/.config/shutdown.sh

Now, pressing and holding the button - or calling 'Power off system' from the Power options menu, will completely power off the RPi.

A momentary press of the button will power it up again.