Automated Data Relay with Data Streams Transmitter

First, deploy a DataStreamsFeed.sol contract, which receives, verifies, and stores the data relayed by the Transmitter.

1. Install Foundry, or update it to the latest version by running foundryup in your terminal.

2. Clone the chainlink-transmitter-contract repository and navigate into the directory:

   git clone https://github.com/woogieboogie-jl/chainlink-transmitter-contract.git
   cd chainlink-transmitter-contract
   

3. Install the dependencies using pnpm and install/initialize Foundry:

     pnpm add --save-dev @openzeppelin/contracts @chainlink/contracts && curl -L https://foundry.paradigm.xyz | bash && forge install
   

4. Create a .env file in the project's root directory to store your private key, RPC URL, and link token address:

   cat >.env <<EOF
   PRIVATE_KEY="<0xYOUR_PRIVATE_KEY>"
   RPC_URL_AVAX_FUJI="<https://...>"
   LINK_TOKEN="0x5947BB275c521040051D82396192181b413227A3"
   EOF
   

   Replace 0xYOUR_PRIVATE_KEY with your actual wallet private key and <https://...> with the RPC URL for the Avalanche Fuji network.

   The LINK_TOKEN address for Avalanche Fuji is 0x5947BB275c521040051D82396192181b413227A3. Refer to the Chainlink documentation for LINK token addresses on other networks.

5. Load the environment variables into your current shell session:

   source .env
   

6. Configure script/DeployDataStreamsFeed.s.sol.

   This script deploys the DataStreamsFeed contract, which will receive data from the Transmitter.

   You must set the constructor arguments for the contract:

   Parameter	Value	Description
   verifierProxyAddress	0x2bf612C65f5a4d388E687948bb2CF842FFb8aBB3	Avalanche Fuji Verifier
   feedId	0x000359843a543ee2fe414dc14c7e7920ef10f4372990b79d6361cdc0dd1ba782	ETH/USD
   decimals	18	The number of decimals for the data.
   description	"ETH / USD Feed"	A human-readable description for the feed.

7. Deploy the contract via the command line.

   Run the deployment script to deploy to Avalanche Fuji:

    forge script script/DeployDataStreamsFeed.s.sol:DeployDataStreamsFeed \
      --rpc-url $RPC_URL_AVAX_FUJI \
      --private-key $PRIVATE_KEY \
      --broadcast
   

   After deployment, copy the Deployed Contract Address and ABI from the output. You will need them to configure the Transmitter.

   • Contract Address: Find the contract address in your terminal output under deployedAddress.
   • Contract ABI: Foundry saves the ABI in out/DataStreamsFeed.sol/DataStreamsFeed.json.

   Before we can use the Transmitter, we need to fund this contract with LINK.

8. Fund the contract with LINK.

   After deployment, transfer some testnet LINK to the feed contract address, which allows the contract to pay for verification fees.

   # Example using cast to transfer 5 LINK (18 decimals)
   cast send $LINK_TOKEN "transfer(address,uint256)" \
       <DEPLOYED_FEED_ADDRESS> 5000000000000000000 \
       --rpc-url $RPC_URL_AVAX_FUJI \
       --private-key $PRIVATE_KEY
   

With a consumer contract on-chain, you can now set up the Transmitter service to relay data to it.

1. In a new terminal window, navigate to your development space and clone the Data Stream Transmitter repository:

   git clone https://github.com/hackbg/chainlink-datastreams-transmitter.git
   cd chainlink-datastreams-transmitter
   

2. Install the project dependencies using npm:

   npm install
   

3. Copy the example environment file:

   cp .env.example .env
   

4. Open your .env file in a text editor and provide the required values:

   Variable	Description
   PRIVATE_KEY	The private key of your developer wallet (ensure this is kept secure and not shared).
   DATASTREAMS_CLIENT_ID	Your Data Streams client ID.
   DATASTREAMS_CLIENT_SECRET	Your Data Streams client secret.

5. Create the runtime configuration file by copying the example:

   cp config-chainlink-example.yml config.yml
   

6. Open config.yml in a text editor. Update the targetChains section to point to the contract you deployed on Avalanche Fuji.

   feeds:
     - name: "ETH/USD"
       feedId: "0x000359843a543ee2fe414dc14c7e7920ef10f4372990b79d6361cdc0dd1ba782"
   
   # --- Default Global Settings ---
   
   # The default chainId to use for transactions if not specified in a target.
   chainId: 43113 # Default to Avalanche Fuji
   
   # The maximum gas limit you are willing to spend on a transaction.
   gasCap: "250000"
   
   # Cron expression defining the data update frequency.
   # This example runs every 30 seconds.
   interval: "*/30 * * * * *"
   
   # The minimum price change percentage to trigger an on-chain update.
   # This example is set to 0.1%
   priceDeltaPercentage: 0.001
   
   # --- Chain & Verifier Definitions ---
   
   # A list of all supported blockchain networks with their RPC URLs.
   chains:
     - id: 43113
       name: "Avalanche Fuji Testnet"
       currencyName: "Fuji AVAX"
       currencySymbol: "AVAX"
       currencyDecimals: 18
       rpc: "https://api.avax-test.network/ext/bc/C/rpc" # <-- TODO: Replace with your own reliable RPC URL
       testnet: true
     - id: 421614
       name: "Arbitrum Sepolia"
       currencyName: "Arbitrum Sepolia Ether"
       currencySymbol: "ETH"
       currencyDecimals: 18
       rpc: "https://sepolia-rollup.arbitrum.io/rpc" # <-- TODO: Replace with your own reliable RPC URL
       testnet: true
   
   # The addresses of the official Chainlink Verifier contracts on each network.
   verifierAddresses:
     - chainId: 43113
       address: "0x2bf612C65f5a4d388E687948bb2CF842FFb8aBB3"
     - chainId: 421614
       address: "0x2ff010DEbC1297f19579B4246cad07bd24F2488A"
   
   # --- On-Chain Target Configurations ---
   
   # This section defines which smart contracts to call for each feed on each chain.
   # You can have multiple targets for the same feed.
   targetChains:
     - chainId: 43113 # Target is on Avalanche Fuji
       targetContracts:
         # This configuration sends ETH/USD data to a contract on Fuji
         - feedId: "0x000359843a543ee2fe414dc14c7e7920ef10f4372990b79d6361cdc0dd1ba782"
           address: "0xYourDataStreamsFeedContractOnFuji" # <-- TODO: Update with your deployed contract address
           # The name of the function to call on your smart contract
           functionName: "verifyAndUpdateReport"
           # The arguments the Transmitter should prepare and send to the function
           #   • rawReport          = the unverified payload from the Data Streams websocket
           #   • parameterPayload   = abi.encode(address feeToken) – produced automatically by the transmitter
           functionArgs: ["rawReport", "parameterPayload"]
           # The ABI for the target function, required to encode the transaction
           abi:
             - name: "verifyAndUpdateReport"
               type: "function"
               stateMutability: "nonpayable"
               inputs:
                 - { "internalType": "bytes", "name": "unverifiedReportData", "type": "bytes" }
                 - { "internalType": "bytes", "name": "parameterPayload", "type": "bytes" }
               outputs: []
           # Off-chain verification must run so keep skipVerify false (default)
           skipVerify: false
   

   • Replace 0xYOUR_AVALANCHE_FUJI_CONTRACT_ADDRESS with the address of the contract you deployed in the previous step.
   • The feedId should match the one you set in the contract deployment.
   • Each target block must keep skipVerify: false, functionName: verifyAndUpdateReport, and functionArgs: ["rawReport", "parameterPayload"] to ensure the Transmitter correctly prepares the transaction for on-chain verification.

7. Start the Docker daemon.

   The Docker daemon is required to run the Redis instance that Transmitter uses. Starting the daemon depends on your operating system. Please refer to the Docker documentation for instructions.

8. Run the following command to start the Transmitter and its services in the background:

   docker compose up -d
   

9. Open your web browser and navigate to http://localhost:3000 to access the Transmitter UI. Because you pre-configured the contract in config.yml, the ETH/USD stream on the dashboard should show a Running status.

On the upper-right corner of the page you will find the Chain section. Since the default chain is configured to Avalanche Fuji, you should see that network listed along with details for your wallet.

Field	Description
Current Chain	The current chain, which is where data will be pushed.
Chain ID	The unique numeric identifier for the current chain.
Wallet Address	Your unique wallet address.
Native Token Balance	Your native token balance, which is used to pay for on-chain transaction fees (gas).
LINK Balance	Your LINK token balance, used to pay for Chainlink Data Streams transactions.

Your balance should reflect the amount of testnet LINK and AVAX you have in your wallet. If you need more, you can use the Chainlink Faucet.

On the top-right corner of the page, you will find the Logs section, which contains details for all Transmitter actions. When operating correctly, the log should reflect a clear, step-by-step process for each on-chain update.

Example log output:

[2025-07-01 16:48:44] info: 🩺 Health check endpoint running at http://localhost:8081/ready
[2025-07-01 16:48:44] info: 🚀 running at http://localhost:3000
[2025-07-01 16:48:44] warn: ℹ️ App already configured
[2025-07-01 16:48:44] info: 🏁 Streams have been started
[2025-07-01 16:50:00] info: 🚨 Price deviation detected | ETH/USD: 3450.06$ | 📉 -0.2135% (-7.36$)
[2025-07-01 16:50:00] info: 📆 Scheduled for writing onchain
[2025-07-01 16:50:00] info: ⛽️ Estimated fee: 0.024395523392104215 LINK # This fee is deducted from the contract's LINK allowance, NOT the sender's balance
[2025-07-01 16:50:04] info: ✅ Report verified
[2025-07-01 16:50:06] info: 📝 Prepared verification transaction
[2025-07-01 16:50:07] info: ⌛️ Sending transaction 0xa59aa3e9c7a2cd020d79bd73e6c7f1aca9a576b77edb43ee35180001709fdf43
[2025-07-01 16:50:08] info: ℹ️ Transaction status: success
[2025-07-01 16:50:08] info: 💾 Price stored | ETH/USD: 3450.06$

The Data Streams section lists all Data Streams, their status, and any related contracts. You should see the ETH/USD feed listed here, which was set in the config.yml file.

Field	Description
Stream	The name of the stream. This is the name set by the user for easier tracking and feed identification.
Feed ID	The feed ID. Check Chainlink Data Streams Documentation for a list of supported streams.
Contract	Target contract for the feed on the current chain. Click to open a configuration page where you can define the target contract, functions, and ABI.
Saved price	The latest price recorded on-chain.
Last reported	The latest price reported by the stream.
Status	Current status of the stream. Possible states include: Running, Connecting, Stopping or Stopped.
Remove	Click to remove the stream.

The Schedule section allows you to define how often the Transmitter should push data on-chain, using a cron expression. We have already defined this in the config.yml file, but you can change it here.

The Verifier Contracts section lets you specify contracts that will verify the data being pushed on-chain. The verifier contract for your current network will be automatically selected based on config.yml.

The Price Delta section lets you define the price change threshold that will trigger an on-chain update. We set this in the config.yml file, but you can change this value here.

The Gas Cap section lets you set the maximum gas limit for transactions. We set this in the config.yml file, but you can change it here.