I
spent some hours, last weekend, working to another little step into
my Raspberry Zero camera project. After experimenting remote software
interface possibilities I started building some minimal bare hardware
interface in order to, at least, safely turn on and off the Raspberry
Pi.
A
bare minimum interface
The
bare minimum hardware interface for a Raspberry project is made of a
power push-button and a status LED telling if the device is still
active or it can be safely removed from power.
Plenty
of tutorials are available on the Internet, I mostly followed
instructions from here
and here.
The
power status information is directly provided from the UART pin
without the need of writing additional software. UART must be enabled
in ‘/boot/config.txt’ configuration
file
enable_uart=1
Then I just connected a LED diode between UART pin and ground (trough a current limiting resistor of course).
Also
the wake-up functionality is implemented by briefly connecting GPIO
pin 6 to ground trough a normally-open push button.