Mint & Redeem frxUSD with Blackrock's BUIDL

This guide demonstrates how to use the viem framework in a simple script that enables a user to mint and redeem frxUSD with BUIDL on Ethereum mainnet.

Note: Please ensure the sender and recipient addresses are onboarded to hold BUIDL.

Prerequisites

Before you start building the sample app to perform a frxUSD transfer, ensure you have met the following prerequisites:

Install Node.js and npm
- Download and install Node.js directly or use a version manager like nvm.
- npm is included with Node.js.
Set up a non-custodial wallet (for example, MetaMask)
- You can download, install, and create a MetaMask wallet from its official website.
- During setup, create a wallet on Ethereum mainnet.
- Retrieve the private key for your wallet, as it will be required in the script below.
Fund your wallet with the gas token and BUIDL on the source chain
- For this guide, we will be minting and redeeming frxUSD with BUIDL on Ethereum mainnet. Therefore, you will need to fund your wallet with BUIDL and ETH on Ethereum mainnet.

Project setup

To build the script, first set up your project environment and install the required dependencies.

1. Set up a new project

Create a new directory and initialize a new Node.js project with default settings:

mkdir frxusd-mint-and-redeem-with-buidl
cd frxusd-mint-and-redeem-with-buidl
npm init -y

This also creates a default package.json file.

2. Install dependencies

In your project directory, install the required dependencies, including viem:

npm install dotenv@^16.4.7 viem@^2.23.4

This sets up your development environment with the necessary libraries for building the script. It also updates the package.json file with the dependencies.

3. Add module type

Add "type": "module" to the package.json file:

{
  "name": "frax-mint-and-redeem-with-buidl",
  "version": "1.0.0",
  "type": "module",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node mint-and-redeem.js"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "description": "",
  "dependencies": {
    "dotenv": "^16.4.7",
    "viem": "^2.23.4"
  }
}

4. Configure environment variables

Create a .env file in your project directory and add your wallet private key:

echo "PRIVATE_KEY=your-private-key-here" > .env

Warning: This is strictly for testing purposes. Never share your private key.

Script setup

This section covers the necessary setup for the mint-and-redeem.js script, including defining keys and addresses, and configuring the wallet client for interacting with the source and destination chains.

1. Replace with your private key and wallet address

Ensure that this section of the file includes your private key and associated wallet address. The script also predefines the Mint & Redeem contract address, the frxUSD address, the BUIDL address, the mint amount, and the redeem amount. These definitions are critical for successfully minting and redeeming frxUSD between the intended wallets.

// ============ Configuration Constants ============
 
// Authentication
const PRIVATE_KEY = process.env.PRIVATE_KEY;
const account = privateKeyToAccount(`0x${PRIVATE_KEY}`, { nonceManager });
 
// Mint & Redeem Contract Addresses and Destination EID
const ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN =
  '0xe827abf9f462ac4f147753d86bc5f91e186e4e9c'; // Mint & Redeem contract address using BUIDL
 
// frxUSD and BUIDL Addresses
const ETHEREUM_MAINNET_FRXUSD_ADDRESS = '0xCAcd6fd266aF91b8AeD52aCCc382b4e165586E29'; // frxUSD address on Ethereum mainnet
const ETHEREUM_MAINNET_BUIDL_ADDRESS = '0x7712c34205737192402172409a8f7ccef8aa2aec'; // BUIDL address on Ethereum mainnet
 
// Mint & Redeem Parameters
const MINT_AMOUNT = 10_000_000n; // 10 BUIDL
const REDEEM_AMOUNT = 10_000_000_000_000_000_000n; // 10 frxUSD

2. Set up wallet client

The wallet client configures the appropriate network settings using viem. In this example, the script will be minting and redeeming frxUSD with BUIDL on Ethereum mainnet.

// Set up a wallet client on the source chain
const ethereumClient = createWalletClient({
  chain: mainnet,
  transport: http(),
  account,
});

frxUSD mint & redeem process

The following sections outline the relevant mint & redeem logic of the sample script. In this example, we are minting and redeeming frxUSD with BUIDL on Ethereum mainnet. Follow the steps below to perform the mint & redeem:

1. Approve BUIDL & frxUSD

Before minting, approve BUIDL for the Mint & Redeem contract on Ethereum mainnet so it can pull BUIDL from your wallet. Before redeeming, approve frxUSD for the same contract so it can pull frxUSD. For other assets, use the appropriate contract address from the frxUSD Mint & Redeem addresses page.

async function approveBuidlForMint() {
  console.log('Approving BUIDL for mint...');
  const approveTx = await ethereumClient.sendTransaction({
    to: ETHEREUM_MAINNET_BUIDL_ADDRESS,
    data: encodeFunctionData({
      abi: [
        {
          type: 'function',
          name: 'approve',
          stateMutability: 'nonpayable',
          inputs: [
            { name: 'spender', type: 'address' },
            { name: 'amount', type: 'uint256' },
          ],
          outputs: [{ name: '', type: 'bool' }],
        },
      ],
      functionName: 'approve',
      args: [ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN, MINT_AMOUNT],
    }),
  });
  console.log(`BUIDL Approval Tx: ${approveTx}`);
}
 
async function approveFrxusdForRedeem() {
  console.log('Approving frxUSD for redeem...');
  const approveTx = await ethereumClient.sendTransaction({
    to: ETHEREUM_MAINNET_FRXUSD_ADDRESS,
    data: encodeFunctionData({
      abi: [
        {
          type: 'function',
          name: 'approve',
          stateMutability: 'nonpayable',
          inputs: [
            { name: 'spender', type: 'address' },
            { name: 'amount', type: 'uint256' },
          ],
          outputs: [{ name: '', type: 'bool' }],
        },
      ],
      functionName: 'approve',
      args: [ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN, REDEEM_AMOUNT],
    }),
  });
  console.log(`frxUSD Approval Tx: ${approveTx}`);
}

Both approvals are now explicit: approve BUIDL for mint, approve frxUSD for redeem, both to ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN.

2. Mint frxUSD with BUIDL

After approving BUIDL, mint by calling the Mint & Redeem contract's deposit to receive frxUSD.

async function mintFrxusdWithBuidl() {
  console.log('Minting frxUSD with BUIDL...');
  const txHash = await ethereumClient.sendTransaction({
    to: ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN,
    data: encodeFunctionData({
      abi: [
        {
          inputs: [
            { internalType: 'uint256', name: '_assetsIn', type: 'uint256' },
            { internalType: 'address', name: '_receiver', type: 'address' },
          ],
          name: 'deposit',
          outputs: [{ internalType: 'uint256', name: '_sharesOut', type: 'uint256' }],
          stateMutability: 'nonpayable',
          type: 'function',
        },
      ],
      functionName: 'deposit',
      args: [MINT_AMOUNT, account.address],
    }),
  });
  console.log(`Mint Tx: ${txHash}`);
}

Call await approveBuidlForMint() first, then await mintFrxusdWithBuidl().

3. Redeem frxUSD with BUIDL

After approving frxUSD, redeem by calling the Mint & Redeem contract's redeem to receive BUIDL.

async function redeemFrxusdForBuidl() {
  console.log('Redeeming frxUSD for BUIDL...');
  const txHash = await ethereumClient.sendTransaction({
    to: ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN,
    data: encodeFunctionData({
      abi: [
        {
          inputs: [
            { internalType: 'uint256', name: '_sharesIn', type: 'uint256' },
            { internalType: 'address', name: '_receiver', type: 'address' },
            { internalType: 'address', name: '_owner', type: 'address' },
          ],
          name: 'redeem',
          outputs: [{ internalType: 'uint256', name: '_assetsOut', type: 'uint256' }],
          stateMutability: 'nonpayable',
          type: 'function',
        },
      ],
      functionName: 'redeem',
      args: [REDEEM_AMOUNT, account.address, account.address],
    }),
  });
  console.log(`Redeem Tx: ${txHash}`);
}

Call await approveFrxusdForRedeem() first, then await redeemFrxusdForBuidl().

Build the script

Create a mint-and-redeem.js in your project directory and paste the following. It groups the script setup and helper functions together at the top, followed by the main execution flow.

Note: The wallet must contain mainnet ETH (gas) and BUIDL to mint, and frxUSD to redeem.

mint-and-redeem.js

// ============ Setup (imports, account, client) ============
import 'dotenv/config';
import { createWalletClient, http, encodeFunctionData, nonceManager } from 'viem';
import { privateKeyToAccount } from 'viem/accounts';
import { mainnet } from 'viem/chains';
 
// ============ Configuration Constants ============
 
// Authentication
const PRIVATE_KEY = process.env.PRIVATE_KEY;
const account = privateKeyToAccount(`0x${PRIVATE_KEY}`, { nonceManager });
 
// Mint & Redeem Contract Addresses
const ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN =
  '0xe827abf9f462ac4f147753d86bc5f91e186e4e9c'; // Mint & Redeem contract address using BUIDL
 
// frxUSD and BUIDL Addresses
const ETHEREUM_MAINNET_FRXUSD_ADDRESS = '0xCAcd6fd266aF91b8AeD52aCCc382b4e165586E29'; // frxUSD address on Ethereum mainnet
const ETHEREUM_MAINNET_BUIDL_ADDRESS = '0x7712c34205737192402172409a8f7ccef8aa2aec'; // BUIDL address on Ethereum mainnet
 
// Mint & Redeem Parameters
const MINT_AMOUNT = 10_000_000n; // 10 BUIDL (6 decimals)
const REDEEM_AMOUNT = 10_000_000_000_000_000_000n; // 10 frxUSD (18 decimals)
 
// Wallet client
const ethereumClient = createWalletClient({
  chain: mainnet,
  transport: http(),
  account,
});
 
// ============ Helpers ============
 
// 1) Approve BUIDL for mint
async function approveBuidlForMint() {
  console.log('Approving BUIDL for mint...');
  const approveTx = await ethereumClient.sendTransaction({
    to: ETHEREUM_MAINNET_BUIDL_ADDRESS,
    data: encodeFunctionData({
      abi: [
        {
          type: 'function',
          name: 'approve',
          stateMutability: 'nonpayable',
          inputs: [
            { name: 'spender', type: 'address' },
            { name: 'amount', type: 'uint256' },
          ],
          outputs: [{ name: '', type: 'bool' }],
        },
      ],
      functionName: 'approve',
      args: [ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN, MINT_AMOUNT],
    }),
  });
  console.log(`BUIDL Approval Tx: ${approveTx}`);
}
 
// 2) Mint frxUSD with BUIDL
async function mintFrxusdWithBuidl() {
  console.log('Minting frxUSD with BUIDL...');
  const txHash = await ethereumClient.sendTransaction({
    to: ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN,
    data: encodeFunctionData({
      abi: [
        {
          inputs: [
            { internalType: 'uint256', name: '_assetsIn', type: 'uint256' },
            { internalType: 'address', name: '_receiver', type: 'address' },
          ],
          name: 'deposit',
          outputs: [{ internalType: 'uint256', name: '_sharesOut', type: 'uint256' }],
          stateMutability: 'nonpayable',
          type: 'function',
        },
      ],
      functionName: 'deposit',
      args: [MINT_AMOUNT, account.address],
    }),
  });
  console.log(`Mint Tx: ${txHash}`);
}
 
// 3) Approve frxUSD for redeem
async function approveFrxusdForRedeem() {
  console.log('Approving frxUSD for redeem...');
  const approveTx = await ethereumClient.sendTransaction({
    to: ETHEREUM_MAINNET_FRXUSD_ADDRESS,
    data: encodeFunctionData({
      abi: [
        {
          type: 'function',
          name: 'approve',
          stateMutability: 'nonpayable',
          inputs: [
            { name: 'spender', type: 'address' },
            { name: 'amount', type: 'uint256' },
          ],
          outputs: [{ name: '', type: 'bool' }],
        },
      ],
      functionName: 'approve',
      args: [ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN, REDEEM_AMOUNT],
    }),
  });
  console.log(`frxUSD Approval Tx: ${approveTx}`);
}
 
// 4) Redeem frxUSD for BUIDL
async function redeemFrxusdForBuidl() {
  console.log('Redeeming frxUSD for BUIDL...');
  const txHash = await ethereumClient.sendTransaction({
    to: ETHEREUM_MAINNET_FRXUSD_MINT_AND_REDEEM_BUIDL_CUSTODIAN,
    data: encodeFunctionData({
      abi: [
        {
          inputs: [
            { internalType: 'uint256', name: '_sharesIn', type: 'uint256' },
            { internalType: 'address', name: '_receiver', type: 'address' },
            { internalType: 'address', name: '_owner', type: 'address' },
          ],
          name: 'redeem',
          outputs: [{ internalType: 'uint256', name: '_assetsOut', type: 'uint256' }],
          stateMutability: 'nonpayable',
          type: 'function',
        },
      ],
      functionName: 'redeem',
      args: [REDEEM_AMOUNT, account.address, account.address],
    }),
  });
  console.log(`Redeem Tx: ${txHash}`);
}
 
// ============ Main ============
async function main() {
  const command = process.argv[2];
  switch (command) {
    case 'mint-with-buidl':
      console.log('Running mint with BUIDL...');
      await approveBuidlForMint();
      await mintFrxusdWithBuidl();
      break;
    case 'redeem-for-buidl':
      console.log('Running mint with BUIDL...');
      await approveFrxusdForRedeem();
      await redeemFrxusdForBuidl();
      break;
    default:
      console.error(
        'Invalid command. Please use "mint-with-buidl" or "redeem-for-buidl".',
      );
      process.exit(1);
  }
  console.log('Mint and redeem completed!');
}
 
main().catch(console.error);

Test the script

To test minting frxUSD with BUIDL, run the following command:

node mint-and-redeem.js mint-with-buidl

To test redeeming frxUSD with BUIDL, run the following command:

node mint-and-redeem.js redeem-for-buidl

Once the script runs and the mint & redeem operations are finalized, the confirmation receipts are logged in the console.

What's next

Mint and redeem frxUSD with Superstate's USTB Mint and redeem frxUSD with WisdomTree's WTGXX