Using Data Feeds Offchain (Stellar)

Chainlink Data Feeds are the quickest way to access market prices for real-world assets. This guide demonstrates how to read Chainlink Data Feeds on the Stellar Testnet offchain using a Soroban RPC simulation with the Stellar CLI and the Stellar JavaScript SDK. To learn how to use Data Feeds in your onchain Soroban contracts, see the Using Data Feeds Onchain guide.

To get the full list of Chainlink Data Feeds on Stellar, see the Price Feed Contract Addresses page with Stellar selected.

Available data feeds on Stellar

The following table shows all available data feeds on Stellar. Each feed is identified by its data_id (the Feed ID), which you pass to the proxy contract to read that feed's data.

Prerequisites

Before you begin, you should have:

• Familiarity with Stellar and Soroban smart contracts
• Understanding of how Chainlink Data Feeds on Stellar work, including the data_id addressing scheme

Requirements

To complete this guide, you'll need:

• Stellar CLI: Install the Stellar CLI. Run stellar --version to verify your installation.

• Node.js 18 or higher: Install Node.js. Run node --version to verify your installation.

Read a feed with the Stellar CLI

You can read a Chainlink Data Feed offchain without deploying a contract by simulating a call to the proxy contract using the stellar contract invoke command with the --send=no flag. This does not submit a transaction and requires no XLM.

The proxy contract exposes a latest_round function that takes a data_id and a decimals parameter, and returns the most recent round for that feed. You pass the data_id as raw hex (without the 0x prefix), and 18 for the decimals parameter unless the feed is served at a reduced precision.

1. Run the following command, replacing <SOURCE_ACCOUNT> with any Stellar account public key. The proxy contract on Stellar Testnet is CBUF6IADAWPWIDWRTHJNINKXHG2UTIQ6TU2F2HRAXWAI7OT3KJPKK6O4, and the BTC/USD data_id is 01a0b4d920000332000000000000000000000000000000000000000000000000:

   stellar contract invoke \
   --id CBUF6IADAWPWIDWRTHJNINKXHG2UTIQ6TU2F2HRAXWAI7OT3KJPKK6O4 \
   --source-account <SOURCE_ACCOUNT> \
   --network testnet \
   --send=no \
   -- latest_round \
   --data_id "01a0b4d920000332000000000000000000000000000000000000000000000000" \
   --decimals 18
   

   Expect an output similar to the following:

   {"answer":"84421629086034400000000","round_id":96,"timestamp":1790274329}
   

   Where:

   • answer is the latest BTC/USD price with 18 decimal places (84421629086034400000000 = 84421.63).
   • round_id is the unique identifier of the round.
   • timestamp is the observation timestamp in Unix seconds when the answer was produced.

   You can find the data_id for each feed on the Price Feed Contract Addresses page with Stellar selected.

Read a feed with the Stellar JavaScript SDK

You can also read a Chainlink Data Feed offchain using the Stellar JavaScript SDK with a Soroban RPC query. This example uses the contract.Client API available in SDK v17 and later.

1. Create a new directory for your project and initialize it:

   mkdir stellar-offchain && cd stellar-offchain && npm init -y
   

2. Install the Stellar JavaScript SDK:

   npm install @stellar/stellar-sdk
   

3. Create a read-feed.js file with the following contents. This script queries the proxy contract's latest_round function for a given data_id:

   const { contract } = require("@stellar/stellar-sdk")
   
   const proxy = "CBUF6IADAWPWIDWRTHJNINKXHG2UTIQ6TU2F2HRAXWAI7OT3KJPKK6O4"
   const dataId = "01a0b4d920000332000000000000000000000000000000000000000000000000"
   
   async function readLatestRound() {
     const client = await contract.Client.from({
       contractId: proxy,
       rpcUrl: "https://soroban-testnet.stellar.org",
       networkPassphrase: "Test SDF Network ; September 2015",
     })
     const result = await client.latest_round({ data_id: Buffer.from(dataId, "hex"), decimals: 18 })
     const round = result.result.value
     console.log("Latest round:", {
       round_id: round.round_id.toString(),
       answer: round.answer.toString(),
       timestamp: round.timestamp.toString(),
     })
   }
   
   readLatestRound().catch(console.error)
   

   The data_id argument is a 32-byte value, passed as a Buffer object. The decimals argument is required and requests the precision at which the answer is returned; pass 18 unless the feed is served at a reduced precision. The latest_round function returns a Round object wrapped in an Ok value, so you access it with result.result.value.

4. Run the script:

   node read-feed.js
   

   Expect an output similar to the following:

   Latest round: {
     round_id: '96',
     answer: '84421629086034400000000',
     timestamp: '1790274329'
   }
   

   Where answer is the latest BTC/USD price with 18 decimal places (84421629086034400000000 = 84421.63).