WinUsb_WriteIsochPipe function (winusb.h)

The WinUsb_WriteIsochPipe function writes the contents of a caller-supplied buffer to an isochronous OUT endpoint, starting on a specified frame number.

Syntax

BOOL WinUsb_WriteIsochPipe(
  [in]           WINUSB_ISOCH_BUFFER_HANDLE BufferHandle,
  [in]           ULONG                      Offset,
  [in]           ULONG                      Length,
  [in, out]      PULONG                     FrameNumber,
  [in, optional] LPOVERLAPPED               Overlapped
);

Parameters

[in] BufferHandle

An opaque handle to the transfer buffer that was registered by a previous call to WinUsb_RegisterIsochBuffer.

[in] Offset

Offset into the buffer relative to the start the transfer.

[in] Length

Length in bytes of the transfer buffer.

[in, out] FrameNumber

On input, indicates the starting frame number for the transfer. On output, contains the frame number of the frame that follows the last frame used in the transfer.

[in, optional] Overlapped

Pointer to an OVERLAPPED structure used for asynchronous operations.

Return value

WinUsb_WriteIsochPipe returns TRUE if the operation succeeds. Otherwise this function returns FALSE, and the caller can retrieve the logged error by calling GetLastError.

Remarks

WinUsb_WriteIsochPipe packetizes the transfer buffer so that in each 1ms interval, the host can send the maximum bytes allowed per interval. The maximum bytes is as specified by the endpoint descriptor for full and high-speed endpoints, and endpoint companion descriptor for SuperSpeed endpoints. If the caller submits multiple write requests to stream data to the device, the transfer size should be a multiple of the maximum bytes per interval (as returned by WinUsb_QueryPipeEx) * 8 / interval.

Because of the transfer packaging used in the underlying kernel-mode interface, the lowest latency notification to an application or driver is 1ms intervals.

Requirements

See also

Send USB isochronous transfers from a WinUSB desktop app

WinUSB Functions