I have installed cloud connector to a server that SQL is installed and I have a couple of databases.
I want to create a native Android app in SMP on SHCP in and use some of the data stored in my on premise SQL server.
Do I have to write an OData service provider?
Does Cloud Connector provides data from DB as OData automatically?
I have experience from SMP 2.3 with MBOs but I don't understand how the new platform works.
Is there a really helpful documentation/tutorial?
Do i have to write an ODATA service provider?
No, the only limitation is that you need to provide an HTTP-based API. Plain REST services or SOAP would work as well, for instance. You will need to provide OData in order to leverage the Offline enablement features, however. Christoph's suggestion of replicating and generating OData from HANA would be one valid approach. You could also use SAP Landscape Transform for the same purpose.
Does Cloud Connector provides data from DB as OData automatically?
No, SAP Cloud Connector works like a VPN tunnel between your cloud tenant and your on-premise systems. It does not have any API-related features.
Since OData is also backed by Microsoft, I would also assume that SQL Server supports ways of generating OData feeds from your database. This is not my home turf, but this post on generating WCF OData services might be relevant?