Device Io Control; A.1 Device Io Control - Advantech TPC-31 User Manual

There is a built-in watchdog timer in the TPC-31/61 series. You can access it through
the WIN32 API. TPC-31/61 panel computers provide a WDT driver to allow users to
enable/disable the Watchdog timer. The driver name is "WDT1:". Programmers must
open this driver before using the resources. Then programmers can use Device IO
Control functions to enable/disable Watchdog timer. The introduction below includes
the Device IO Control, the definition of the parameter and an example.
A.1

Device IO Control

This function sends a control code directly to a specified device driver, causing the
corresponding device to perform the specified operation.
BOOL DeviceIoControl(
HANDLE hDevice,
DWORD dwIoControlCode,
LPVOID lpInBuffer,
DWORD nInBufferSize,
LPVOID lpOutBuffer,
DWORD nOutBufferSize,
LPDWORD lpBytesReturned,
LPOVERLAPPED lpOverlapped );
Parameters:
 hDevice
[in] Handle to the device that is to perform the operation. Call the CreateFile
function to obtain a device handle.
 dwIoControlCode
[in] Specifies the control code for the operation. This value identifies the specific
operation to be performed and the type of device on which the operation is to be
performed. No specific values are defined for the dwIoControlCode parameter.
However, the writer of a custom device driver can define IOCTL_XXXX control
codes, per the CTL_CODE macro. These control codes can then be advertised,
and an application can use these control codes with DeviceIoControl to perform
driver-specific functions.
lpInBuffer

[in] Long pointer to a buffer that contains the data required to perform the opera-
tion. This parameter can be NULL if the dwIoControlCode parameter specifies
an operation that does not require input data.
 nInBufferSize
[in] Size, in bytes, of the buffer pointed to by lpInBuffer.
 lpOutBuffer
[out] Long pointer to a buffer that receives the operation's output data. This
parameter can be NULL if the dwIoControlCode parameter speci-fies an opera-
tion that does not produce output data.
nOutBufferSize

[in] Size, in bytes, of the buffer pointed to by lpOutBuffer.
 lpBytesReturned
[out] Long pointer to a variable that receives the size, in bytes, of the data stored
into the buffer pointed to by lpOutBuffer. The lpBytesRe-turned parameter can-
not be NULL. Even when an operation produces no output data, and lpOutBuf-
fer can be NULL, the DeviceIoControl function makes use of the variable
pointed to bylpBytesReturned. After such an operation, the value of the variable
is without meaning.
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