ethereum-gsheets-telegram-raspi-messaging

DIY: Build Stupid and Crazy Expensive Messaging for LED Switches

This repo contains the Spring Boot messaging modules for all three messaging options (Google Sheets, Telegram Bot, Ethereum/Gnosis Chain) mentioned in the accompanying blog post.

Setup

Build Locally

Prerequisites

• Java 11+
• (Opt.) Java IDE like IntelliJ IDEA, Eclipse or VS Code

Build executable JAR

• Clone this repository
• Run gradlew build in root folder
• Generated executable JAR raspi-messaging-0.0.1-SNAPSHOT.jar is in build\libs

Start on Raspberry Pi

Note: Pi4j must be invoked as sudo

sudo `which java` -jar raspi-messaging-0.0.1-SNAPSHOT.jar --spring.config.location=./application.properties --spring.profiles.active=prod

Configure Messaging

You can choose between the Messaging types GoogleSheet,TelegramBot, or Web3 by modifying the application.properties.

web3.module.enabled=${WEB3_MODULE_ENABLED:true}
gsheet.module.enabled=${GSHEET_MODULE_ENABLED:false}
tgram.module.enabled=${TELEGRAM_MODULE_ENABLED:false}

In the sample configuration above, Web3 is enabled by default.
However, all parameters have to be set by setting the environment variables.

Web3 Messaging

For Web3 Messaging, these parameters have to be set:

web3.ethereum.rpc.url=${ETHEREUM_NODE_IP_PORT:https://dai.poa.network/}
web3.switch.contract.address=${ETHEREUM_CONTRACT}
web3.mnemonic=${ETHEREUM_MNEMONIC:test test test test test test test test test test test junk}

• For the Ethereum RPC Url, you can look at http://pokt.network or use https://dai.poa.network/ for testing purposes.
• The Gnosis Chain contract address (if not set, contract is deployed)
• Mnemonic for account address, which is used to derive the private keys of the accounts

Solidity Smart Contract

We are using a dumb (smart) contract here. A dumb contract is a smart contract pattern that takes advantage of Events, and their relative cheapness compared to writing to storage. Read more about Dumb Contracts here: https://anallergytoanalogy.medium.com/adventures-with-dumb-contracts-18f8ce8414c9

We can save money here as we are only interested in the Event SwitchTurned with the state 0:off, 1:on, or 2:blink and the sender, which we use to differentiate between devices.

With this setup, you can even reuse the already deployed contract at 0x192FaabCf853eA9da3AC92471989A1608E1f2676 if you scan for both arguments (in our setup, only state is evaluated).

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

contract Switch {

    address creator;

    event SwitchTurned(address indexed sender, uint8 indexed state);

    constructor() {
        creator = msg.sender;
    }

    function turnSwitch(uint8 state) public {
        emit SwitchTurned(msg.sender, state);
    }

}

• Write the Smart Contract function turnSwitch, eg. in the Remix IDE (https://remix.ethereum.org/) or the Blockscout Gnosis Chain Explorer (https://blockscout.com/)

After a successful transaction, the Event turnSwitch is emitted as the only instruction in the function is emit SwitchTurn(...)

GoogleSheet Messaging

For GoogleSheet Messaging,

• Go to Dashboard at https://console.cloud.google.com/
• Create new project
• Go to Google Cloud Console, Activate GSheet API

• Create GSheet, Share with “Anyone with link” for Viewer

• Create Form for GSheet to switch values

• Get API Key: https://developers.google.com/sheets/api/guides/authorizing#APIKey

Note: Restrict Key to Google Sheet

• Configure Properties spreadsheetId, range, and key

All necessary properties are configured in the application.properties.

Authenticate Google Sheet API Calls

We are using an HttpExecuteInterceptor to set the API key to the HTTP Requests to authenticate for the calls.

key = "AIzaSyAA1ZnStXXXXXXXXXXXXXXXXXXXXXXXX";

HttpRequestInitializer httpRequestInitializer =
request -> request.setInterceptor(
        intercepted -> intercepted.getUrl().set("key", key));

service = new Sheets.Builder(
    GoogleNetHttpTransport.newTrustedTransport(), 
    JSON_FACTORY, 
    httpRequestInitializer)
.setApplicationName(APPLICATION_NAME)
.build();

TelegramBot Messaging

• Create the Bot (we used raspi_led_switch, if you use it, you switch our LED)

• Invite Bot raspi_led_switcher to a Group or chat with it directly

Note: In your Bot, make sure that not everybody can use it, eg. by restricting it to a specific chatId.