WARNING!
The PiPower board is outputting 5V, which can kill your Pi according
to the specs.

Either add a logic level converter chip or a simple resistor based
voltage divider:


                    2.2k    3.3k
  PiPower signal ---~~~--+--~~~--- GND
                         |
                         |
                        GPIO

Source: https://www.raspberrypi.org/forums/viewtopic.php?f=45&t=22841



To install as a service, save pipower.service to /lib/systemd/system/ and execute:

sudo chmod 644 /lib/systemd/system/pipower.service
sudo systemctl daemon-reload
sudo systemctl enable pipower.service
sudo systemctl start pipower.service



Please check /boot/config.txt for a line defining enable_uart.
If this is set to 0, change it to 1! If not defined, add it just
to be sure:

enable_uart=1

I have encountered this default of 0 in RetroPie, but I've seen
reports for a standard installation as well:
https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=141195