Saahithi Chillara Radhika Goyal ECE Fall Senior Design Project

Introduction BitSR is a payment solution for Bitcoin users and automated vending machines. A way for users to wirelessly make payments when they come near a vending machine. It is a cost efficient way for merchants to increase modes of revenue Eliminating service fees imposed on payments done with credit cards 2Senior Design Project

Background: Bitcoins Senior Design Project3

Objective To devise a system that allows customers to use Bitcoins by connecting to a vending machine with wifi. 4Senior Design Project

Features Interface with Bitcoin Blockchain Easy to fit into existing vending machines using the ubiquitous MultiDrop Bus Phone Application that supports secure transactions Locating Vending Machines that accept Bitcoins Senior Design Project5

High Level Design - Software 6Senior Design Project Figure 1: system diagram

7Senior Design Project Figure 2: Transaction Flow Diagram

Component 1: Phone Application Senior Design Project8

Phone Application The Phone App is the client application developed using the Meteor JavaScript framework. The user interface of the App on the mobile phone is designed to be responsive and automatically scales to different form factors. Senior Design Project9 Figure 3: Log in

Phone Application Design Requirements: The phone application supports log in authentication for a user’s account linking multiple Bitcoin addresses to their BitSR account synchronizing changes with the server in real time connecting with the RaspberryPi using WiFi Senior Design Project10

Phone Application 11 Figure 4: Add Bitcoin Account Figure 6: All Tabs Figure 5: All Bitcoin Accounts

Component 2: BitSR Server Senior Design Project12

BitSR Server 13Senior Design Project Figure 7: BitSR server home page

BitSR Server Design Requirements: Maintain Account information of the users who sign in using Phone Updates the transaction database whenever a purchase is done Processes prepaid transfers and batch transfers Senior Design Project14

BitSR Server 15Senior Design Project Figure 8: BitSR Transfers

BitSR Server - Security There are three main roles to provide secure access to information stored on the server. 1. Admin role 2. Merchant Role 3. User Role 16Senior Design Project

Component 3: Raspberry Pi Senior Design Project17

Raspberry Pi 18Senior Design Project

Raspberry Pi 19Senior Design Project Figure 9: Setting up the rPi

Raspberry Pi Requirements: Interact with Phone Application through WiFi to make transactions Send Purchase information (Price, location of purchase) to the BitSR server via HTTP protocol Receive response from BitSR server and indicate Success or Failure Transmit Success or Failure to Vending Machine Controller using the MultiDropBus Protocol. Senior Design Project20

Raspberry Pi: Hearbeat 21Senior Design Project Figure 10: rPi sends heartbeat to BitSR

Raspberry Pi: Transaction Status Senior Design Project22 Figure 11: rPi’s transaction is registered

Raspberry Pi: Slave State Machine Senior Design Project23 Figure 12: Peripheral FSM

Component 4: MultiDrop Bus Senior Design Project24

MultiDrop Bus Senior Design Project25 Design Requirements: Communicate between the raspberry pi and the vending machine controller Step down 35 V from Vending Machine to 5 V for Raspberry Pi Create Isolation between Transmit and Receive Signals

MultiDrop Bus: Schematic Senior Design Project26 Pin 1: 35 V Pin 2: Ground Pin 3: Master Receive Pin 4: Comm. Common Pin 5: Master Transmit Figure 13: Electrical Component

Component 5: Bitcoin Interface Senior Design Project27

BitCoin Interface: Private Network To simulate a test network, open source Bitcoin developer software is forked from GITHUB. To create private bitcoin testnet for developer applications: 1. The docker container needs to installed 2. docker pull freewil/bitcoin-testnet-box 3. docker build -t bitcoin-testnet-box 4. docker run -t -i freewil/bitcoin-testnet-box 28Senior Design Project

BitCoin Interface 29Senior Design Project Figure 14: Bitcoun Balance BeforeFigure 15: Bitcoun Balance After

Successes and Challenges Currently the server does not send back the vend success or failure. However, with manual intervention, the entire transaction does go through 35 to 5 v step down gets extremely hot even though the voltage output is correct With our current setup, the end-to-end vending time was less than 5 seconds Senior Design Project30

Ethical Concerns No significant physical hazards to Merchants while installation or to Users while managing transactions Managing integrity and confidentiality while handling funds of users’ BitSR balance accounts Using Meteor’s in-built functionality to isolate privilege levels between Admin, Merchant and Users Senior Design Project31

Conclusion and future work Port onto a cloud server Communicate with a real vending machine Run further tests to ensure circuit doesn’t overheat Update the maps functionality Senior Design Project32

Questions Senior Design Project33

Thank you! Senior Design Project34