There are two ways to transmit data, using the 'low' level read/write API or the 'high' level transfer API.
- Low level API
- To transmit data to the host, the class driver should call usb_write(). Upon completion the registered endpoint callback will be called. Before sending another packet the class driver should wait for the completion of the previous write. When data is received, the registered endpoint callback is called. usb_read() should be used for retrieving the received data. For CDC ACM sample driver this happens via the OUT bulk endpoint handler (cdc_acm_bulk_out) mentioned in the endpoint array (cdc_acm_ep_data).
- High level API
- The usb_transfer method can be used to transfer data to/from the host. The transfer API will automatically split the data transmission into one or more USB transaction(s), depending endpoint max packet size. The class driver does not have to implement endpoint callback and should set this callback to the generic usb_transfer_ep_callback.
.. doxygengroup:: _usb_device_core_api