DIO ReadFile

hartensteiner · Jul 2nd 2009

Hello,

iÃ‚Â´ve tested the DIO Driver and have some problems while implementing.
The output functions working well over WriteFile(), but input reading via ReadFile()
makes some trouble. It ended every time with errorcode 12 ( ERROR_INVALID_ACCESS )

Code

[DllImport("coredll.dll")]
private static extern int ReadFile(IntPtr hFile, byte[] lpBuffer, int nNumberOfBytesToRead, out int lpNumberOfBytesRead, IntPtr lpOverlapped);
public string ReadInput()
{
System.Text.Encoding encoding = System.Text.Encoding.Default;
int ptr_read = ReadFile(handle, buffer, 1, ref read, IntPtr.Zero);
if (ptr_read != 0)
{
return encoding.GetString(buffer,0,1);
}
return "";
}

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Any Solutions ?

best reguards

Ch. Hartensteiner

fs-support_DK · Jul 2nd 2009

Hello,

how do you create the handle?
Is the handle valid?

DKuhne.

hartensteiner · Jul 2nd 2009

Hello DKuhne,

the handel is created via CreateFile and is valid. The SetOutput routine called before the ReadInput routine
is working with the same handle.

Code

public bool Open()
{
handle = CreateFile("DIO1:", GENERIC_WRITE, 0, System.IntPtr.Zero, OPEN_EXISTING, 0, System.IntPtr.Zero);
if (handle != System.IntPtr.Zero)
return true;
else
return false;
}
public void Close()
{
CloseHandle(handle);
}
public void WriteOutput(string hex)
{
buffer[0] = byte.Parse(hex, System.Globalization.NumberStyles.HexNumber);
WriteFile(handle, buffer, 1, ref written, System.IntPtr.Zero);
}

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Is there any problem working with the same handle ?

Chris

fs-support_DK · Jul 2nd 2009

Hello,

you use GENERIC_WRITE as dwDesiredAccess!

In case you want to read from driver you need to use GENERIC_READ also.

You can use:

Code

(GENERIC_READ | GENERIC_WRITE)

DKuhne.

hartensteiner · Jul 7th 2009

Thanks DKuhne,

now it works ...

Chris

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