Coffee Order Web User Interface

A very large hammer to crack a very small nut!

Background

I'm an early riser and always bring my wife a coffee when she wakes up. Instead of her calling out for one, or even ringing a bell, what better way than to employ one of my Raspberry Pi Zeros (and a tacky, £1.50 plastic palm tree with LED lights)?

The RPi0 serves up a webpage with three buttons:

order a coffee
acknowledge order [me]
acknowledge receival of coffee [wife]

When the Order button is pressed, it lights up the palm tree; Acknowledge button updates order status; and the Receive button turns it off and resets the system - simples!

Prerequisites

sudo apt install python3-pip
pip3 install flask

Photos and Screenshots

Photos

Screenshots

Architecture

Python Flask is used to serve a web page and provide RESTful APIs.

The single web page uses Javascript to call various APIs to order and receive a coffee.

The python server tracks order status in a global variable, so that I can acknowledge the order from another computer.

The web page regularly polls the python server for the order status, so my wife knows I have received the order.

Python GPIO is used to turn on/off power to the LEDs.

Various scripts are run on system startup from:

/etc/rc.local

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

# Print the IP address
_IP=$(hostname -I) || true
if [ "$_IP" ]; then
  printf "My IP address is %s\n" "$_IP"
fi


sudo /home/trevorde/coffeeServer/index.py &

exit 0

[optional] Prevent wifi going to sleep

iw wlan0 set power_save off

this is persistent across reboots
do not do this in rc.local as network interface may not be initialised

[optional] To minimise file corruption, make file system read-only:
https://medium.com/swlh/make-your-raspberry-pi-file-system-read-only-raspbian-buster-c558694de79

very difficult to update system
date (bash script + python) function returns incorrect date+time

Further work