Chainlink Ropsten Instructions

This guide will allow you to create and deploy a consuming contract to fulfill a data request using our deployed oracle contract. You do not need to run a node yourself in order to follow these instructions.

Additional Guides

• Running your own Chainlink node on Ropsten

Tools

This guide requires the following tools:

• Metamask
• Remix

General Overview

Interacting with contracts that require data from Chainlink follow a common workflow:

• Deploy a requesting contract
• Fund the requesting contract with LINK
• Call the function within the requesting contract to create a Chainlink run
  • This transfers LINK from the requesting contract to the oracle contract
• Retrieve the value from the consuming contract

The examples included here have the requesting and consuming contracts as the same contract. If you wanted the answer to be supplied to a different contract, you would change the word this and the function signature in the line below to that of the consuming contract:

ChainlinkLib.Run memory run = newRun(PRICE_SPEC_ID, this, "fulfillEthereumPrice(bytes32,uint256)");

Setup

It is recommended to use the Beta version of Metamask for this guide. Accessing the beta can be accomplished by clicking on the (☰) icon, then "Try Beta!" The interface should reload, and you will see the new look.

Add the Ropsten LINK token to Metamask:

• Switch to the "Ropsten Test Net" network in Metamask
• Click on the (☰) icon
• Click Add Token button
• Click the Custom Token tab
• Paste the contract address 0x20fE562d797A42Dcb3399062AE9546cd06f63280
• The rest should fill in, if it doesn't the Token Symbol is LINK and use 18 for Decimals

• Click Next

You should now see LINK listed on the Ropsten Test Network, finish by clicking the last "Add Tokens" button.

Faucets

With your Metamask wallet set up, you'll need some Ropsten ETH and LINK to work with.

Ropsten ETH

• http://faucet.ropsten.be:3001/
• https://faucet.metamask.io/

Ropsten LINK

• https://developers.smartcontract.com/faucet

Contract Deployment

This section of the guide uses Remix in order to compile and deploy an example contract from the examples/ropsten/contracts directory.

In Remix, import the RopstenConsumer.sol contract at chainlink/examples/ropsten/contracts

• Click on the RopstenConsumer.sol contract in the left side-bar
• On the Compile tab, click on the "Start to compile" button near the top-right

• Change to the Run tab
• RopstenConsumer should already be selected
• Click Deploy

• Metamask will prompt you to Confirm the Transaction
• You will need to choose a Gas Price (use 20 if you don't know what to pick)
• Select Submit

• A link to Etherscan will display at the bottom, you can open that in a new tab to keep track of the transaction

• Once successful, you should have a new address for the deployed contract

Funding the contract

With the contract deployed, you will need to send some Ropsten LINK to it in order to create a request.

• Click the icon with the red box around it in the Remix interface to copy the address.

• Then in Metamask, click the (☰) icon, then the LINK token
• Click the Send button
• Paste the address into the "To:" line

Metamask will update the status to confirmed when the transaction is complete.

Calling the contract

In Remix, you can interact with and call the requesting functions directly, by supplying a string for the methods that begin with "request".

• Type "USD" in the requestEthereumPrice text input, and click on its button.

• Scroll down if required and click the Confirm button

• And after a few blocks, the updated value retrieved by Chainlink will be visible for each of the requestEthereum* methods that were requested