---
title: Price Oracle — Chainlink-backed
description: JustLend DAO PriceOracle reference — getUnderlyingPrice, assetPrices, setPrice (poster-only). Backed by Chainlink Data Feeds. Prices are scaled by 10^(tokenDecimal − 6) in sun (10⁻⁶ TRX).
---

# Price Oracle

!!! info "About this page"
    * **Protocol:** JustLend DAO
    * *Network:** TRON Mainnet 
    * **Pattern:** `PriceOracleProxy` (entrypoint, `TGnYnSn4G9PgWFj7QQemh4YMZKp3fkympJ`) → `PriceOracle` (impl, `TMiNCmvD3zdsv6mk7niBU6NPBzVNjYMQTV`)
    * **Data source:** [Chainlink](https://chain.link/) Data Feeds. The `poster` address relays Chainlink prices on-chain via `setPrice(asset, price)`
    * **Units:** Prices are denominated in **TRX** , scaled by `1e^(33 - tokenDecimal)`. For an 18-decimal token like USDD, the value for the price feed is calculated based on the exchange rate of 1 USDD to TRX (assuming a price of 3.0266), Price Feed Value = 3.0266 * 1e^(33 - 18) = 3.0266 * 1e^15
    * **ABI:** [`abis/price-oracle.json`](../abis/price-oracle.json).

Blockchain-powered smart contracts, by design, cannot access external market data directly. To ensure accurate and tamper-resistant pricing, the JustLend DAO protocol relies on a multi-source data aggregation system that draws from reputable and decentralized sources.

[Chainlink](https://chain.link/) Data Feeds are the key component of this process, helping to strengthen the security and reliability of pricing across markets.


`PriceOracle.sol:` allows users to:

* Price Poster
* Get Asset Price
* Set Price

The source code is available on [Github](https://github.com/justlend/justlend-protocol/blob/main/contracts/PriceOracle/PriceOracleV1.sol).


## **Contracts ABI**

### **Anchor Token Price**
Calling this methods returns the current price anchor of a specified token.
``` solidity
function anchors(address) view returns(uint256, uint256)
```

* **Parameter description:**
    * `token:` the address of the underlying token(e.g. TR7NHqjeKQxGTCi8q8ZY4pL8otSzgjLj6t for USDT).
* **Returns:**
    * `period:` the current time period. Calculated as: current block height/ 600 (the TRON network produces approx. 600 blocks per 30 mins);
    * `priceMantissa:` the current price of the token in TRX, scaled by 1e^(33 - tokenDecimal).


### **Price Poster**
Calling this methods returns the current price poster.
``` solidity
function poster() view returns(address)
```

* **Parameter description:** N/A.
* **Returns:** Address of the current poster.


### **Asset Prices**
Calling this method returns the current price of the specified asset.
``` solidity
function assetPrices(address asset) public view returns (uint)
```

* **Parameter description:**
    * `asset:` the address of the token to query.
* **Returns:** the current price of the token in TRX, scaled by 1e^(33 - tokenDecimal).


### **Get Price**
Calling this method returns the current price of the specified asset.
``` solidity
function getPrice(address asset) public view returns (uint)
```

* **Parameter description:**
    * `asset:` the address of the token to query.
* **Returns:** the current price of the token in in TRX, scaled by 1e^(33 - tokenDecimal).


### **Set Price (poster-only)**
Calling this methods set a token price for the current time period.
``` solidity
function setPrice(address asset, uint requestedPriceMantissa) public returns (uint)
```

* **Parameter description:**
  * `asset:` the address of the underlying token (e.g. TR7NHqjeKQxGTCi8q8ZY4pL8otSzgjLj6t for USDT);
  * `requestedPriceMantissa:` new price, scaled by 10^27.
* **Returns:** 0 for success, otherwise an error code.