Feeder Pools

Feeder Pools are 50/50 AMMs, usually consisting of one mAsset and another mAsset-like asset. Feeder Pools are an extension of the mStable ecosystem and allow for more assets to swap and mint.

Ethereum Mainnet

Main Contracts

mUSD/alUSD Feeder Pool	0x4eaa01974B6594C0Ee62fFd7FEE56CF11E6af936
mUSD/GUSD Feeder Pool	0x4fb30c5a3ac8e85bc32785518633303c4590752d
mUSD/BUSD Feeder Pool	0xfe842e95f8911dcc21c943a1daa4bd641a1381c6
mUSD/RAI Feeder Pool (NonPeggedFeederPool)	0x36f944b7312eac89381bd78326df9c84691d8a5b
mUSD/FEI Feeder Pool	0x2F1423D27f9B20058d9D1843E342726fDF985Eb4
mBTC/HBTC Feeder Pool	0x48c59199da51b7e30ea200a74ea07974e62c4ba7
mBTC/TBTC Feeder Pool (deprecated)	0xb61a6f928b3f069a68469ddb670f20eeeb4921e0
mBTC/tBTCv2 Feeder Pool	0xc3280306b6218031E61752d060b091278d45c329

Peripheral Contracts

Contracts	Address
Feeder Wrapper	0x7C1fD068CE739A4687BEe9F69e5FD2275C7372d4
Feeder Interest Validator	0xf1049aeD858C4eAd6df1de4dbE63EF607CfF3262
Feeder Logic	0x2837C77527c37d61D9763F53005211dACB4125dE
Feeder Manager	0x90aE544E8cc76d2867987Ee4f5456C02C50aBd8B

Ethereum Mainnet Integration Contracts

Integration Contracts

Contracts	Address
BUSD Feeder Pool Aave Integration	0xac98ffc901d6bB634be06f6d3fE63893b1aF6535
BUSD Feeder Pool Iron Bank (CREAM) Integration for mUSD	0x2A15794575e754244F9C0A15F504607c201f8AfD
GUSD Feeder Pool Aave Integration	0xd51f062104D7c8eE7dB100878A454451ADFD2811
GUSD Feeder Pool Iron Bank (CREAM) Integration for mUSD	0xaF007D4ec9a13116035a2131EA1C9bc0B751E3cf
RAI Feeder Pool Aave Integration	0x8cc6a1ae38743d453f2522c5228b775d145f43b7
FEI Feeder Pool Aave Integration	0x4094AeC22f40F11c29941d144C3DC887B33f5504

Feeder Pool tokens follow the ERC20 standard. The non-standard decreaseAllowance and increaseAllowance functions have been added to mitigate the well-known issues around setting allowances. These are based on the OpenZeppelin ERC20 implementation.

ERC-20 Functions

totalSupply()

function totalSupply () external returns (uint256)

Returns the amount of tokens in existence.

balanceOf()

function balanceOf () external returns (uint256)

Returns the amount of tokens owned by account.

transfer()

function transfer () external returns (bool)

Moves amount tokens from the caller's account to recipient.

Returns a boolean value indicating whether the operation succeeded.

Emits a {Transfer} event.

allowance()

function allowance () external returns (uint256)

Returns the remaining number of tokens thatspenderwill be allowed to spend on behalf ofownerthrough {transferFrom}. This is zero by default.

This value changes when {approve} or {transferFrom} are called.

approve()

function approve () external returns (bool)

Sets amount as the allowance of spender over the caller's tokens.

Returns a boolean value indicating whether the operation succeeded.

IMPORTANT: Beware that changing an allowance with this method brings the risk that someone may use both the old and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards: https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729

Emits an {Approval} event.

transferFrom()

function transferFrom () external returns (bool)

Moves amount tokens from sender to recipient using the allowance mechanism. amount is then deducted from the caller's allowance.

Returns a boolean value indicating whether the operation succeeded.

Emits a {Transfer} event.

increaseAllowance()

function increaseAllowance () public returns (bool)

Atomically increases the allowance granted to spender by the caller.

This is an alternative to {approve} that can be used as a mitigation for problems described in {IERC20-approve}.

Emits an {Approval} event indicating the updated allowance.

Requirements:

• spender cannot be the zero address.

decreaseAllowance()

function decreaseAllowance () public returns (bool)

Atomically decreases the allowance granted to spender by the caller.

This is an alternative to {approve} that can be used as a mitigation for problems described in {IERC20-approve}.

Emits an {Approval} event indicating the updated allowance.

Requirements:

• spender cannot be the zero address.

• spender must have allowance for the caller of at least

  subtractedValue.

Feeder Pool Functions

mint()

function mint (address _input, uint256 _inputQuantity, uint256 _minOutputQuantity, address _recipient) external returns (uint256 mintOutput)

Mint fpTokens with a single bAsset. This contract must have approval to spend the senders bAsset. Supports either fAsset, mAsset or mpAsset as input - with mpAssets used to mint mAsset before depositing.

Parameter	Type	Description
_input	address	Address of the bAsset to deposit.
_inputQuantity	uint256	Quantity in input token units.
_minOutputQuantity	uint256	Minimum fpToken quantity to be minted. This protects against slippage.
_recipient	address	Receipient of the newly minted fpTokens

mintMulti()

function mintMulti (address[] _inputs, uint256[] _inputQuantities, uint256 _minOutputQuantity, address _recipient) external returns (uint256 mintOutput)

Mint fpTokens with multiple bAssets. This contract must have approval to spend the senders bAssets. Supports only fAsset or mAsset as inputs.

Parameter	Type	Description
_inputs	address[]	Address of the bAssets to deposit.
_inputQuantities	uint256[]	Quantity in input token units.
_minOutputQuantity	uint256	Minimum fpToken quantity to be minted. This protects against slippage.
_recipient	address	Receipient of the newly minted fpTokens

getMintOutput()

function getMintOutput (address _input, uint256 _inputQuantity) external returns (uint256 mintOutput)

Get the projected output of a given mint.

Parameter	Type	Description
_input	address	Address of the bAsset to deposit
_inputQuantity	uint256	Quantity in bAsset units

getMintMultiOutput()

function getMintMultiOutput (address[] _inputs, uint256[] _inputQuantities) external returns (uint256 mintOutput)

Get the projected output of a given mint

Parameter	Type	Description
_inputs	address[]	Non-duplicate address array of addresses to bAssets to deposit for the minted mAsset tokens.
_inputQuantities	uint256[]	Quantity of each bAsset to deposit for the minted fpToken.

swap()

function swap (address _input, address _output, uint256 _inputQuantity, uint256 _minOutputQuantity, address _recipient) external returns (uint256 swapOutput)

Swaps two assets - either internally between fAsset<>mAsset, or between fAsset<>mpAsset by first routing through the mAsset pool.

Parameter	Type	Description
_input	address	Address of bAsset to deposit
_output	address	Address of bAsset to withdraw
_inputQuantity	uint256	Units of input bAsset to swap in
_minOutputQuantity	uint256	Minimum quantity of the swap output asset. This protects against slippage
_recipient	address	Address to transfer output asset to

getSwapOutput()

function getSwapOutput (address _input, address _output, uint256 _inputQuantity) external returns (uint256 swapOutput)

Determines both if a trade is valid, and the expected fee or output. Swap is valid if it does not result in the input asset exceeding its maximum weight.

Parameter	Type	Description
_input	address	Address of bAsset to deposit
_output	address	Address of bAsset to receive
_inputQuantity	uint256	Units of input bAsset to swap

redeem()

function redeem (address _output, uint256 _fpTokenQuantity, uint256 _minOutputQuantity, address _recipient) external returns (uint256 outputQuantity)

Burns a specified quantity of the senders fpToken in return for a bAsset. The output amount is derived from the invariant. Supports redemption into either the fAsset, mAsset or assets in the mAsset basket.

Parameter	Type	Description
_output	address	Address of the bAsset to withdraw
_fpTokenQuantity	uint256	Quantity of LP Token to burn
_minOutputQuantity	uint256	Minimum bAsset quantity to receive for the burnt fpToken. This protects against slippage.
_recipient	address	Address to transfer the withdrawn bAssets to.

redeemProportionately()

function redeemProportionately (uint256 _inputQuantity, uint256[] _minOutputQuantities, address _recipient) external returns (uint256[] outputQuantities)

Credits a recipient with a proportionate amount of bAssets, relative to current vault balance levels and desired fpToken quantity. Burns the fpToken as payment. Only fAsset & mAsset are supported in this path.

Parameter	Type	Description
_inputQuantity	uint256	Quantity of fpToken to redeem
_minOutputQuantities	uint256[]	Min units of output to receive
_recipient	address	Address to credit the withdrawn bAssets

redeemExactBassets()

function redeemExactBassets (address[] _outputs, uint256[] _outputQuantities, uint256 _maxInputQuantity, address _recipient) external returns (uint256 fpTokenQuantity)

Credits a recipient with a certain quantity of selected bAssets, in exchange for burning the relative fpToken quantity from the sender. Only fAsset & mAsset (0,1) are supported in this path.

Parameter	Type	Description
_outputs	address[]	Addresses of the bAssets to receive
_outputQuantities	uint256[]	Units of the bAssets to receive
_maxInputQuantity	uint256	Maximum fpToken quantity to burn for the received bAssets. This protects against slippage.
_recipient	address	Address to receive the withdrawn bAssets

getRedeemOutput()

function getRedeemOutput (address _output, uint256 _fpTokenQuantity) external returns (uint256 bAssetOutput)

Gets the estimated output from a given redeem

Parameter	Type	Description
_output	address	Address of the bAsset to receive
_fpTokenQuantity	uint256	Quantity of fpToken to redeem

getRedeemExactBassetsOutput()

function getRedeemExactBassetsOutput (address[] _outputs, uint256[] _outputQuantities) external returns (uint256 fpTokenQuantity)

Gets the estimated output from a given redeem

Parameter	Type	Description
_outputs	address[]	Addresses of the bAsset to receive
_outputQuantities	uint256[]	Quantities of bAsset to redeem

getPrice()

function getPrice () public returns (uint256 price, uint256 k)

Gets the price of the fpToken, and invariant value k

getConfig()

function getConfig () external returns (struct FeederConfig config)

Gets all config needed for general InvariantValidator calls

getBasset()

function getBasset (address _bAsset) external returns (struct BassetPersonal personal, struct BassetData vaultData)

Get data for a specific bAsset, if it exists

Parameter	Type	Description
_bAsset	address	Address of bAsset

getBassets()

function getBassets () external returns (struct BassetPersonal[], struct BassetData[] vaultData)

Get data for a all bAssets in basket