Application note - Example code for capturing power button event on fitlet2 running Linux

From fit-PC wiki
Revision as of 08:34, 17 October 2018 by Denis (Talk | contribs) (Configure power button event handling)

(change visibility) (diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search
  • This application note provides an example of how to capture a power button click event on Linux.
  • It has been tested with the below setup:
Device: fitlet2
CPU: Intel(R) Atom(TM) Processor E3950
BIOS: 09/17/2018 American Megatrends Inc. FLT2.
OS: Debian Buster (testing)
Kernel: 4.16.0-2-amd64
ISO: debian-buster-DI-alpha3-amd64-netinst.iso

fitlet2: required BIOS settings

  • Press [Delete] button after power-on to enter BIOS settings
  • Set BIOS -> Main -> OS selection to [Linux]

Configure power button event handling

  • Login as root user (root password required):
$ su -
  • Ignore power button events handling by systemd, then reboot:
$ sed -i s/".*HandlePowerKey.*"/"HandlePowerKey=ignore"/ /etc/systemd/logind.conf
$ reboot
  • Install ACPI related software:
$ apt install acpi-support-base acpid
  • Verify acpi events are visible in the system, run acpi_listen command and press power button 2-3 times:
$ acpi_listen
button/power PBTN 00000080 00000000
button/power LNXPWRBN:00 00000080 00000007
button/power PBTN 00000080 00000000
button/power LNXPWRBN:00 00000080 00000008

NOTE #1: current power button handler is /etc/acpi/, but it does not work for some reason

NOTE #2: there are 2 events PBTN and LNXPWRBN, we need to handle only one of them, for example PBTN

  • Create custom power button event rule:
$ cat > /etc/acpi/events/powerbtn-custom-rule << EOF
event=power (PBTN)
  • Create custom power button event handler and make it executable:
$ cat > /etc/acpi/ << EOF
echo  "Hello from PBTN!" > /dev/tty1

$ chmod +x /etc/acpi/
  • Restart acpid service to activate the new functionality:
$ service acpid restart
  • Press power button shortly, you should see "Hello from PBTN!" on the main console