Cannot communicate successfully with USB HID device using writefile()

问题

I am fairly new to C# as well as windows programming and I am attempting to establish communication between a USB HID device and an app written in c# on a windows xp pc. I have obtained the device path successfully and have used this to establish a valid Handle on the device:

IntPtr drive = CreateFile(devicePath, GENERIC_READ | GENERIC_WRITE,
               FILE_SHARE_READ | FILE_SHARE_WRITE, IntPtr.Zero,
               OPEN_EXISTING, FILE_FLAG_DELETE_ON_CLOSE, IntPtr.Zero);

This proved to be a valid handle that yields a positive integer when tested. After creating the handle I call 'HidD_GetPreparsedData' and 'HidP_GetCaps' which yield a struct previously imported (HIDP_CAPS) that stores specific data related to the device attached. Next, I try to call writefile():

bool success = WriteFile(drive, ref outputReportBuffer, 
               caps.OutputReportByteLength, ref numberOfBytesWritten, 
               IntPtr.Zero);

drive: The Handle of the device

outputReportBuffer:The array of bytes to write [65]

caps.OutputReportByteLength: The amount of bytes to write, caps is the struct of HIDP_CAPS

numberOfBytesWritten: hardcoded to 0

IntPtr.Zero: Everything I have read passes this last parameter as I have done. In the formal parameters of 'writefile' the last parameter is listed as 'IntPtr ipOverlapped', but I have not been able to figure out what that is, except that It should be passed as some form of 0

How WriteFile is imported:

[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool WriteFile(IntPtr hFile, 
ref byte[] lpBuffer, 
uint nNumberOfBytesToWrite,
ref uint lpNumberOfBytesWritten, 
IntPtr ipOverlapped);

When writefile is executed it simply does nothing. I get no error, but when tested, it reveals that communication was never established and it was not successful. If anyone could share any knowledge or provide any resources to help I would really appreciate it. Thank you for reading.

Regards.

回答1:

Remove the ref in your WriteFile declaration.

While http://www.pinvoke.net/ is a great resource for P/Invoke declarations, it's a wiki-style website and many declarations are wrong (often they won't work on a x64 machine).

来源：https://stackoverflow.com/questions/11691619/cannot-communicate-successfully-with-usb-hid-device-using-writefile

标签

usb

hid