CPI to ECC using OData or REST API

Hi CPI Experts,

I have a requirement to send IDocs (Purchase Order) to SAP ECC/S4 HANA system from CPI & also receive IDocs (Invoice, ASN) from the ERP System. The mode of communication needs to be using OData or REST API instead of using IDoc or SOAP Adapter.

Do I need to build any Custom APIs in the API Portal or there is some other way to acheive this?

Please let me know if anybody has implemented a similar use case or if there is any help document to guide me through the whole process.

Thanks in Advance.