Chainlink is a decentralized oracle network that allows smart contracts to securely access external data and APIs. It provides smart contracts with data from outside sources through oracle nodes that query, verify, and authenticate external data feeds. Chainlink has built-in price feeds and adapters that allow smart contracts to request data from nodes paid in LINK tokens. The document demonstrates a smart contract using Chainlink to request ETH price data from an API and receive the response once fulfilled.

1. CHAINLINK
DECENTRALIZED
ORACLE NETWORK
By Gene Leybzon
7/1/2021

2. WHAT ARE ORACLES?
A blockchain oracle is a third-party service that provides
smart contracts with information from the outside world. It
is the layer that queries, verifies, and authenticates
external data sources, usually via trusted APIs and then
relays that information.

3. CHAINLINK VISION:
ANY INPUT, ANY BLOCKCHAIN, ANY
OUTPUT

4. UNDER THE HOOD

5. CHAINLINK COMMON USE CASES
Pre-Built Decentralized Price Feeds
A Verifiable Random Function
Modular External Adapters

6. DATA FEEDS

7. PRICE AGGREGATOR

8. SMART CONTRACT INTEGRATION
WITH ORACLE

9. DEMO “TIME” Alarm Clock

10. USE CASE
AlarmClockSample.so
l
Alarm Requestor
requestAlarmClock()
sendChainlinkRequestTo()
fulfillAlarm()
AlarmForMeetup

11. PLAN
o Compile Alarm Requestor code
oDeploy to Kovan testnet
oTransfer $LINK to contract to pay for the service
oSet alarm
oWait for alarm

12. ALARM CONSUMER SMART
CONTRACT

13. SENDING SOME $LINK TO THE OUR
CONTRACT

14. REQUESTING AN ALARM
/** * Receive the response in the form of uint256 */
event AlarmForMeetup(bytes32 _requestId, uint256 _volume);
function fulfillAlarm(bytes32 _requestId, uint256 _volume) public
recordChainlinkFulfillment(_requestId) {
alarmDone = true;
emit AlarmForMeetup( _requestId, _volume);
}

15. CHECKING REQUEST STATUS

16. CHECKING EVENTS

17. CALLING ANY API CryptoCompare

18. MAKING GET FROM SMART
CONTRACT
https://min-api.cryptocompare.com/data/pricemultifull?fsyms=ETH&tsyms=USD

19. SMART CONTRACT CODE -
REQUEST
function requestVolumeData() public returns (bytes32 requestId)
{
Chainlink.Request memory request = buildChainlinkRequest(jobId, address(this),
this.fulfill.selector);
request.add("get", "https://min-
api.cryptocompare.com/data/pricemultifull?fsyms=ETH&tsyms=USD");
request.add("path", "RAW.ETH.USD.VOLUME24HOUR");
int timesAmount = 10**18;
request.addInt("times", timesAmount); // remove decimals
// Sends the request
return sendChainlinkRequestTo(oracle, request, fee);
}

20. SMART CONTRACT CODE –
RESPONSE
/**
* Receive the response in the form of uint256
*/
function fulfill(bytes32 _requestId, uint256 _volume) public
recordChainlinkFulfillment(_requestId)
{
volume = _volume;
}

21. LINK TOKENOMICS “LINK” token

22. $LINK TOKEN PRICE STATISTICS

23. $LINK TOKEN
1.$LINK token is ChainLink’s native
cryptocurrency and was set up on the
Ethereum network using an ERC677
2.Chainlink nodes are paid in $LINK tokens only
3.$LINK tokens are used as collateral value

24. WANT TO LEARN MORE ABOUT
CHAINLINK?
https://www.reddit.com/r/Chainlink/
https://chainlinklabs.com/jobs

25. QUESTIONS?

26. STAY IN TOUCH
Gene Leybzon https://www.linkedin.com/in/leybzon/
https://www.meetup.com/members/90744
20/
https://www.leybzon.com