This repository hosts the software bits of a candy dispenser build with Arduino and utilizing Bitcoin as the payment mechanism. It uses code from the this project: https://github.com/javgh/greenaddress-pos-tools/ .

• install dependencies: python-qrencode, python-qt4
• add "server=1" (but not daemon=1) to bitcoin.conf and configure rpcuser & rpcpassword
• create the file $HOME/.arduino-bitcoin-candyrc with this contents:

{
    "arduino_port": "/dev/ttyUSB0", 
    "candy_currency": "USD", 
    "candy_price": 2.0, 
    "exchange_rate_ticker": {
        "field": "last", 
        "interval": 5, 
        "source": "MtGox.com", 
        "url": "https://mtgox.com/api/0/data/ticker.php"
    }, 
    "green_addresses": {
        "1CDysWzQ5Z4hMLhsj4AKAEFwrgXRC8DqRN": "Verified by Instawallet."
    }, 
    "rpc_url": "http://rpcuser:rpcpassword@127.0.0.1:8332"
}

• upload the sketch arduino/trigger_via_serial/trigger_via_serial.ino to your Arduino
• run: python pos-tool.py

You should see two windows popping up: The merchant back end and the customer display. Clicking on "Init demo" will display a new Bitcoin address and associated QR code. The tool then listens for transactions to the Bitcoin address and as soon as it receives something, it changes the display to read "Payment received" and sends a signal to the Arduino.

• looping the demo
• checking for correct amount and dealing with cases where not enough or too much was payed
• any kind of double-spend detection/prevention mechanism (besides green addresses)