Creating halt/wake button?

Question

I have rigged up a wake-from-halt button using pins 5 and 6. These two pins, when connected, will reset power and reboot from halt. I want to use this same button, if I can, to run a command that, when pressed, will shut down the computer using sudo halt. Would this be possible? For the sudo halt button, I would need to connect from GPIO 1 to the button, then split to GPIO 6 (ground) and a general GPIO pin. I don't know if it is possible/safe to connect GPIO 5 to this either.

score 8 · Accepted Answer · answered Jan 25 '14 at 11:54

8

No need to add other GPIO pins. You could just use the same pins for your halt-button.

Here is some python code that will poll pin 5. When the button is presses pin 5 is pulled to ground (pin 6), and the code will read a LOW. In that case is will run the halt command

#!/usr/bin/python
import RPi.GPIO as GPIO
import time
import subprocess

GPIO.setmode(GPIO.BOARD)
# set pin 5 to input, and enable the internal pull-up resistor
GPIO.setup(5, GPIO.IN, pull_up_down=GPIO.PUD_UP)

oldButtonState1 = True
while True:
    buttonState1 = GPIO.input(5)

    if buttonState1 != oldButtonState1 and buttonState1 == False :
        # print "Button 1 pressed"
        subprocess.call("halt", shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)

    oldButtonState1 = buttonState1

    time.sleep(.1)

PS. I didn't know about the Wake from Halt function. Thanks to you I know now! So thanks.

answered Jan 25 '14 at 11:54

Gerben

2,420
14
17

1

Brilliant! I didn't realize that I could do it all on just 5 and 6. Thank you! :) – Ryan McClure Jan 26 '14 at 04:37
So, we both learned something today (-: – Gerben Jan 26 '14 at 15:28
More of a note to myself. You could even modify the code to have a press do a reboot, and a press-and-hold to do a shutdown (or vice versa). – Gerben Jan 26 '14 at 20:11
In what way is your script running continuously, i.e., daemonized? Have you noticed any decrease in performance when watching movies? – athanassis Oct 30 '14 at 05:58
@athanassis It only runs 10 times a second. 100ms is a very long time, CPU land. That's like 80000000 clock cycles. I guesstimate it uses around 0.1% CPU or less. – Gerben Oct 30 '14 at 16:31
1

Indeed, it's very long time, but not when CPU hits 100% for a few secs when, e.g., decoding a full HD movie. I'll give it a try, testing never hurts. Thanks for the feedback! – athanassis Oct 30 '14 at 18:36

score 2 · Answer 2 · answered Mar 22 '14 at 06:25

A reset button can be attached to the P6 header, with which the Pi can be reset. Momentarily shorting the two pins of P6 together will cause a soft reset of the CPU (which can also 'wake' the Pi from halt/shutdown state)

c.f.

RPi Low-level peripherals - eLinux.org http://elinux.org/RPi_Low-level_peripherals#P6_header
Making a Reset Switch for your Rev 2 Raspberry Pi » RasPi.TV http://raspi.tv/2012/making-a-reset-switch-for-your-rev-2-raspberry-pi

score 0 · Answer 3 · answered Oct 10 '17 at 07:22

0

Using overlays worked great for me. http://www.stderr.nl/Blog/Hardware/RaspberryPi/PowerButton.html

answered Oct 10 '17 at 07:22

John Shearing

271
3
12

Creating halt/wake button?

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