17.6.4.4 Communication Endpoints
Endpoint 0 is used for the enumeration process.
Endpoint 1 (64-byte Bulk OUT) and endpoint 2 (64-byte Bulk IN) are used as communication endpoints.
SAM-BA Boot commands are sent by the host through Endpoint 1. If required, the message is split into several data payloads by the host driver.
If the command requires a response, the host sends IN transactions to pick up the response.