WinUsb_ReadIsochPipe routine

The WinUsb_ReadIsochPipe function reads data from an isochronous OUT endpoint.

Syntax

BOOL __stdcall WinUsb_ReadIsochPipe(
  _In_      PWINUSB_ISOCH_BUFFER_HANDLE BufferHandle,
  _In_      ULONG Offset,
  _In_      ULONG Length,
  _Inout_   PULONG FrameNumber,
  _In_      PULONG NumberOfPackets,
  _Out_     PULONG IsoPacketDescriptors,
  _In_opt_  LPOVERLAPPED Overlapped
);

Parameters

BufferHandle [in]

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

Offset [in]

Offset into the buffer relative to the start the transfer.

Length [in]

Length in bytes of the transfer buffer.

FrameNumber [in, out]

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.

NumberOfPackets [in]

Total number of isochronous packets required to hold the transfer buffer. Also indicates the number of elements in the array pointed to by IsoPacketDescriptors.

IsoPacketDescriptors [out]

An array of USBD_ISO_PACKET_DESCRIPTOR structures. After the transfer completes, each element contains the status and size of the isochronous packet.

Overlapped [in, optional]

Pointer to an OVERLAPPED structure used for asynchronous operations.

Return value

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

Remarks

WinUsb_ReadIsochPipe packetizes the transfer buffer so that in each interval, the host can receive 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 read requests to stream data from the device, the transfer size should be a multiple of the maximum bytes per interval (as returned by WinUsb_QueryPipeEx) * 8 / interval.

Requirements

See also

WinUSB Functions

Send USB isochronous transfers from a WinUSB desktop app

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Build date: 12/5/2013