Programming Info D2XXPG31.pdf

FT-Win32 API Functions765.3 FT_W32_ReadFileRead data from the device.BOOL FT_W32_ReadFile(FT_HANDLE ftHandle, LPVOID lpBuffer, DWORD dwBytesToRead,LPDWORD lpdwBytesReturned, LPOVERLAPPED lpOverlapped)ParametersftHandlelpBufferdwBytesToReadlpdwBytesReturnedlpOverlappedHandle of the device.Pointer to a buffer that receives the data from the device.Number of bytes to read from the device.Pointer to a variable that receives the number of bytes readfrom the device.Pointer to an overlapped structure.Return ValueIf the function is successful, the return value is nonzero.If the function is unsuccessful, the return value is zero.RemarksThis function supports both non-overlapped and overlapped I/O, except under Windows CEwhere only non-overlapped IO is supported.Linux does not support the W32 API.Non-overlapped I/OThe parameter, lpOverlapped, must be NULL for non-overlapped I/O.This function always returns the number of bytes read in lpdwBytesReturned.This function does not return until dwBytesToRead have been read into the buffer. The number ofbytes in the receive queue can be determined by calling FT_GetStatus 34 orFT_GetQueueStatus 31 , and passed as dwBytesToRead so that the function reads the device andreturns immediately.When a read timeout has been setup in a previous call to FT_W32_SetCommTimeouts 94 , thisfunction returns when the timer expires or dwBytesToRead have been read, whichever occurs first.If a timeout occurred, any available data is read into lpBuffer and the function returns a non-zerovalue.An application should use the function return value and lpdwBytesReturned when processing thebuffer. If the return value is non-zero and lpdwBytesReturned is equal to dwBytesToRead then thefunction has completed normally. If the return value is non-zero and lpdwBytesReturned is lessthen dwBytesToRead then a timeout has occurred, and the read request has been partiallycompleted. Note that if a timeout occurred and no data was read, the return value is still non-zero.A return value of FT_IO_ERROR suggests an error in the parameters of the function, or a fatalerror like USB disconnect has occurred.© Future Technology Devices International Ltd. 2005