USB Function Controller Driver Transfers (Windows CE 5.0)
The following table shows the types of USB function controller driver transfers.
| Transfer type | Description |
|---|---|
| Isochronous | Used when the client identifies that the host regularly sends packets of 1 KB or less to its OUT endpoint. Packets of 1 KB or less are sent due to transmission errors. The maximum packet size is 1024 bytes.
The client calls IssueVendorTransfer with USB_OUT_TRANSFER and a 1024 byte buffer. Calling IssueVendorTransfer four times ensures that when one transfer is retired, another queues immediately. When the client receives notification that a transfer has completed, it checks the count of bytes transferred and the transfer status with GetTransferStatus. It then closes the transfer with CloseTransferHandle, processes the data, and calls IssueVendorTransfer again to recycle the buffer. |
| Bulk | Used when the client identifies that the host sends packets of 64 KB to its OUT endpoint. The maximum packet size of these packets is 512 bytes. Bulk transfer is also used when the client knows that the host requests packets of 64 KB from its IN endpoint. The maximum size of these packets is 512 bytes.
The client calls IssueVendorTransfer with a 64 KB buffer and the appropriate IN or OUT flag. The function controller driver retires the transfer after the buffer is full or after it receives a short packet. |
| Interrupt | Used when the client identifies that the host sends packets of up to 8 bytes to its OUT endpoint. The maximum size of these packets is 8 bytes.
The client calls IssueVendorTransfer with USB_OUT_TRANSFER and an 8 byte buffer. When IssueVendorTransfer receives any packet of zero to 8 bytes, the transfer is retired. |
| DMA | Used when the client driver identifies the interface type and bus number for which to translate the physical address. Additionally, it must know any type of alignment guarantees. For more information, see the UFN_PDD_INFO structure. |
See Also
USB Function Controller Drivers
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