Start by placing the stacking header onto the Pi Zero, then place four standoffs. Make sure the standoffs you use are the same size as the stacking header.
When you're using a JuiceBox Zero with your Pi, you need to stop using the micro usb port on the Pi. Trying to power the Pi Zero directly could damage the Pi Zero or the JuiceBox Zero. So place a USB cover (or kapton) tape over the USB charging port on the Pi.
The low battery LED will light up when the battery voltage reaches 3.2V. At this time, the GPIO16 pin will go HIGH. So in order to safely shutdown the Pi when the battery is low, we'll run a script in the background that listens for a rising edge on pin 16, then shuts down the Pi.
So first, use your editor to create a new file called
safeshutdown.py in the
/home/pi directory. Add the following:
import os import RPi.GPIO as GPIO GPIO.setmode(GPIO.BCM) shutdown_pin = 16 GPIO.setup(shutdown_pin, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) def shutdown_callback_function( shutdown_pin ): os.system("shutdown -h now") GPIO.add_event_detect( shutdown_pin, GPIO.RISING, callback=shutdown_callback_function, )
Refer to the JuiceBox Zero Github Repository for more details.
Now, edit the crontab by typing the following in a shell:
sudo crontab -e
And add the following to the end of the file:
@reboot python /home/pi/safeshutdown.py &
This will cause the
safeshutdown.py script to run in the background when the system boots. It will listen for a rising edge on pin 16, and then shutdown the Pi safely!