The redeem function converts a specified quantity of oTokens into the underlying asset, and returns them to the user. The amount of underlying tokens received is equal to the quantity of oTokens redeemed, multiplied by the current Exchange Rate. The amount redeemed must be less than the user's Account Liquidity and the market's available liquidity.
OErc20 / OEther
function redeem(uint redeemTokens) returns (uint)
OEther oToken = OEther(0x3FDB...);
require(oToken.redeem(7) == 0, "something went wrong");
const oToken = OErc20.at(0x3FDA...);