Shut down OPi Zero using a push button on GPIO

[Aditya]

Hi there.

I want to use a push button on a GPIO to shutdown O Pi Zero safely.  Though the acpid way runs fine on an O Pi One, I wonder if there is a way to make it work on a O Pi Zero. Please direct me if its documented somewhere already. Thanks

[martinayotte]

Beware that even if you trigger event from GPIO to execute "halt" command using a "gpio-key" node in DT, the OPiZero will still be connected to PSU since there is no PMIC to really turn off the power...

[Aditya]

Yeah thats fine for me. Just want to implement that for safe shutdown as I would want to disconnect power after that. So is there simple way to implement that??

[martinayotte]

12 hours ago, Aditya said:

So is there simple way to implement that??

Sure !

Take this overlay source and save it as "gpio-keys.dts" :

 

 

 

/dts-v1/;
/plugin/;

/ {
   compatible = "allwinner,sun8i-h3";

   fragment@0 {
      target = <&pio>;
      __overlay__ {
         keypad_pins: keypad_pins {
            allwinner,pins = "PA10";
            allwinner,function = "gpio_in";
            allwinner,pull = <1>;
         };
      };
   };

   fragment@1 {
      target-path = "/"; // "/soc";
      __overlay__ {
         mykeypad: mykeypad {
            compatible = "gpio-keys";
            #address-cells = <1>;
            #size-cells = <0>;
            pinctrl-names = "default";
            pinctrl-0 = <&keypad_pins>;
            status = "okay";
            button@10 {
               label = "GPIO KEY_POWEROFF";
               linux,code = <0x74>;
               gpios = <&pio 0 10 1>; // PA10, active_low
            };
         };
      };
   };

   __overrides__ {
      mykeypad =     <&mykeypad>,"status";
   };
};
 

 

Compile it as an overlay DTBO using this command :

git-work/dtc/dtc -@ -I dts -O dtb -o /boot/dtb/overlay/sun8i-h3-gpio-keys.dtbo gpio-keys.dts

Then, add this overlay either in /boot/armbianEnv.txt with "overlays=gpio-keys" or by loading it dynamically using :

mkdir /sys/kernel/config/device-tree/overlays/gpiokeys
cat /boot/dtb/overlay/sun8i-h3-gpio-keys.dtbo > /sys/kernel/config/device-tree/overlays/gpiokeys/dtbo

 

As soon as you connect the PA10 pin to GND, it will trigger a "shutdown" ...

[Aditya]

Great ! I would try that right away.
A small query though. Can another button be hooked similar to this for a simple reboot also?

By the way thanks a lot for this. You guys just rock.

[Aditya]

17 minutes ago, martinayotte said:

Compile it as an overlay DTBO using this command :

git-work/dtc/dtc -@ -I dts -O dtb -o /boot/dtb/overlay/sun8i-h3-gpio-keys.dtbo gpio-keys.dts

I am sorry but I am really a noob. Do I need to install something for this purpose?? Because it says this
-bash: git-work/dtc/dtc: No such file or directory

 

[martinayotte]

1 minute ago, Aditya said:

-bash: git-work/dtc/dtc: No such file or directory

Right ! You need to install DT compiler from here : http://ftp.debian.org/debian/pool/main/d/device-tree-compiler/device-tree-compiler_1.4.7-3_armhf.deb

And do not provide this path "git-work/dtc/dtc" but simply "dtc -@ -I dts -O dtb -o /boot/dtb/overlay/sun8i-h3-gpio-keys.dtbo gpio-keys.dts" ...

[Aditya]

Thanks a lot again.

:-)

[martinayotte]

21 minutes ago, Aditya said:

Can another button be hooked similar to this for a simple reboot also?

The <0x74> is KEY_POWER, I've tried <0x198> which seem to be for KEY_RESTART, but it doesn't seem to work ... I will try to dig kernel sources to figure out ...

[Aditya]

9 minutes ago, martinayotte said:

Right ! You need to install DT compiler from here : http://ftp.debian.org/debian/pool/main/d/device-tree-compiler/device-tree-compiler_1.4.7-3_armhf.deb

And do not provide this path "git-work/dtc/dtc" but simply "dtc -@ -I dts -O dtb -o /boot/dtb/overlay/sun8i-h3-gpio-keys.dtbo gpio-keys.dts" ...

After installing that and compiling, it gave a couple of warnings
 

/boot/dtb/overlay/sun8i-h3-gpio-keys.dtbo: Warning (unit_address_vs_reg): /fragment@1/__overlay__/mykeypad/button@10: node has a unit name, but no reg property
/boot/dtb/overlay/sun8i-h3-gpio-keys.dtbo: Warning (avoid_unnecessary_addr_size): /fragment@1/__overlay__/mykeypad: unnecessary #address-cells/#size-cells without "ranges" or child "reg" property

Is that okay

[Aditya]

I short the PA10 pin to ground and its not shutting down.
I have installed wiring pi and by giving command

gpio readall

I can see that PA10 is an input and voltage is high(pullup).
But not shutting down. What could be the reason?

[martinayotte]

21 minutes ago, Aditya said:

Is that okay

It is Okay

[martinayotte]

10 minutes ago, Aditya said:

I short the PA10 pin to ground and its not shutting down.

Strange ... Which kernel are you using ?

Did you loaded the overlay ?

If you try "evtest /dev/input/event0", what are you seeing while putting PA10 to GND ?

[Aditya]

My bad.

It does the job. Thanks a lot.

[martinayotte]

3 minutes ago, Aditya said:

My bad.

It does the job. Thanks a lot.

What was the issue ? Did you forgot to load the overlay ?

[Aditya]

I did but it had asked for permission which I missed somehow. I mean I used sudo but it again said permission denied for half of the command.

 

Later used su command first and then gave loaded it easily.

[martinayotte]

Just now, Aditya said:

Later used su command first and then gave loaded it easily.

Right ! I didn't mentioned it, loading overlay dynamically requires root privileges ...

[Aditya]

Thanks a lot for helping me out. Can you please take a look into the reboot button also.

[martinayotte]

1 hour ago, Aditya said:

Can you please take a look into the reboot button also.

I've look during more than an hour, it deosn't seems to be implemented ...

 

The only other way I would see is to run this python script and add a " os.system("reboot") " after the "button pressed" print :

 

 

#!/usr/bin/env python
"""Read button.

Make gpio input and enable pull-up resistor.
"""

import os
import sys
import time
import logging

if not os.getegid() == 0:
    sys.exit('Script must be run as root')

from pyA20.gpio import gpio
from pyA20.gpio import connector
from pyA20.gpio import port

button = port.PA10

"""Init gpio module"""
gpio.init()

"""Set directions"""
gpio.setcfg(button, gpio.INPUT)

"""Enable pullup resistor"""
gpio.pullup(button, gpio.PULLUP)
#gpio.pullup(button, gpio.PULLDOWN)     # Optionally you can use pull-down resistor


try:
    while True:
        state = gpio.input(button)      # Read button state
#        print (state)
        if state == 0:
            print("button pressed")
            logging.info("button pressed")
        time.sleep(0.2)

except KeyboardInterrupt:
    print ("Goodbye.")
 

 

[Aditya]

Wow. Thanks a lot lot again. You are a life saver.