SMART PSU for ARM SBC

This is a smart power switch for ARM SBC. This provides a gracefull shutdown and power-off for any tiny board computer that support FreeBSD+libgpio.

This tested OK on

• Nanopi Neo
• Nanopi Neo Air
• Orange PI
• Raspberry PI B
• Raspberry PI 3

How it's work?

When plugging in, the board is poweroff and the switch device enter in sleep mode to reduce power consumption. Just press the switch to power on the board. If you press again the button within 1.5 seconds, the board is poweroff immediatly.

In normal operation (when operating system is running), the psud daemon wait for key pressed to perform specified action. The default configuration file is as follow:

# psud configuration file
# $Id$  /etc/psud.conf
PSUD_PIN=3                       # My configuration on NanoPI Neo
PSUD_CMD="/sbin/shutdown -p now"	
PSUD_OPT="Dont Care"             # Nothing special

In /etc/rc.conf, adds the following line

psud_enable="YES"

Start psud

service psud start

So, just press button to gracefully shutdown the system. After the configured delay (by dip-switch), the board is powered-off.

AC Recovery mode

AC Power Recovery Allows you to set how the system reacts after AC power is restored to the system. By default, the AC Power Recovery option is set to "Power OFF". The other option is "last state".

Nanobsd configuration

Since all persistents filesystems are mount read-only, there is no need for graceful shutdown with nanobsd. But you probably need to save your configuration on shutdown. You can achieve this with the following script:

#!/bin/sh
#
# file: /usr/local/bin/save_configuration.sh
#
mount /cfg || exit 1
find /cfg -type f -print | sed -e '/^\/cfg//' | while read f
do
	if [ -f /etc/$f ] ; then
		cp -p /etc/$f /cfg/$f
	fi
done
sync;sync;sync
umount /cfg

Edit /etc/psud.conf as follows:

PSUD_PIN=1                    # Power switch pin, hardware dependent
PSUD_CMD="/usr/local/bin/save_configuration.sh"

PSUD_OPT="WaitAndShot"        # Wait for $PSUD_CMD to complete before
                              # poweroff. GPIO pin is toggle to HIGH 
                              # after $CMD complete . Any other option
                              # is ignored and power off is achieved after
                              # $SHUTDOWN_TIMEOUT

About files

 psud/        psud daemon sources
 kicad/       KiCad schematic
 firmware/    source code for AVR attiny13/13a and atmega328p
 refs/        Some MOSFET-P datasheets

LICENSE

Released under the MIT License