ST AN2328 APPLICATION NOTE

AN2328

Application note

HID device coding example

Introduction

This application note describes how to lookup and use HID devices under Windows. This note is related to the MEMS Evaluation boards which are usually connected via USB and accessed through the MEMS USB Reader software. The following information will assist you in developing your own applications. It provides a section of source code only, however, for a complete project it is necessary to add proper result testing and exception handling.

April 2006

Rev 1

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Coding example	AN2328

1 Coding example

1.1Load HID library

A dynamic loading hid library is used.

	//Pointers to a function are used, therefore:
	typedef VOID		(__stdcall *PHidD_GetProductString)(HANDLE, PVOID, ULONG);
	typedef VOID		(__stdcall *PHidD_GetHidGuid)(LPGUID);
	typedef BOOLEAN (__stdcall *PHidD_GetAttributes)(HANDLE, PHIDD_ATTRIBUTES);
	typedef BOOLEAN (__stdcall *PHidD_SetFeature)(HANDLE, PVOID, ULONG);
	typedef BOOLEAN (__stdcall *PHidD_GetFeature)(HANDLE, PVOID, ULONG);
	HINSTANCE			hHID	= NULL;
	PHidD_GetProductString			HidD_GetProductString	= NULL;
	PHidD_GetHidGuid			HidD_GetHidGuid	= NULL;
	PHidD_GetAttributes			HidD_GetAttributes	= NULL;
	PHidD_SetFeature			HidD_SetFeature	= NULL;
	PHidD_GetFeature			HidD_GetFeature	= NULL;
	//Load the library:
	hHID = LoadLibrary("HID.DLL");
	//Update the pointers:
	HidD_GetProductString = (PHidD_GetProductString)
	GetProcAddress(hHID, "HidD_GetProductString");
	HidD_GetHidGuid			= (PHidD_GetHidGuid)
	GetProcAddress(hHID, "HidD_GetHidGuid");
	HidD_GetAttributes			= (PHidD_GetAttributes)
	GetProcAddress(hHID, "HidD_GetAttributes");
	HidD_SetFeature			= (PHidD_SetFeature)
	GetProcAddress(hHID, "HidD_SetFeature");
	HidD_GetFeature			= (PHidD_GetFeature)
	GetProcAddress(hHID, "HidD_GetFeature");
1.2	Lookup device
	typedef struct _HIDD_ATTRIBUTES
	{
	ULONG	Size;		// = sizeof (struct _HIDD_ATTRIBUTES)
	USHORT	VendorID;
	USHORT	ProductID;
	USHORT	VersionNumber;

} HIDD_ATTRIBUTES, *PHIDD_ATTRIBUTES;

GUID HidGuid; (HidD_GetHidGuid)(&HidGuid); HDEVINFO hDevInfo;

HANDLE DeviceHandle;

//Get information about HIDs try {

hDevInfo = SetupDiGetClassDevs (&HidGuid,NULL,NULL,DIGCF_PRESENT|DIGCF_INTERFACEDEVICE);

if (hDevInfo == INVALID_HANDLE_VALUE) return 0;

} catch (...) {

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AN2328	Coding example

return 0;

}

//Identify each HID interface devInfoData.cbSize = sizeof(devInfoData); DWORD MemberIndex = 0;

bool Result;

while (1)

{

try {

Result = SetupDiEnumDeviceInterfaces (hDevInfo,0,&HidGuid,MemberIndex,&devInfoData);

if (!Result)

{

SetupDiDestroyDeviceInfoList(hDevInfo); return (0); //No more devices found

}

MemberIndex++;

} catch (...) { return 0;

}

//Get the Pathname of the current device

//detailData.cbSize = sizeof(SP_INTERFACE_DEVICE_DETAIL_DATA); detailData.cbSize = 5;

DWORD Reguired = 0;

try {

Result = SetupDiGetDeviceInterfaceDetail (hDevInfo,&devInfoData,&detailData,256,&Reguired,NULL);

if (!Result) continue;

}catch (...) { continue;

}

//Get Handle for the current device try {

DeviceHandle = CreateFile (detailData.DevicePath, GENERIC_READ|GENERIC_WRITE, FILE_SHARE_READ|FILE_SHARE_WRITE, (LPSECURITY_ATTRIBUTES)NULL, OPEN_EXISTING,

0,

NULL);

if (DeviceHandle == INVALID_HANDLE_VALUE)

{

CloseHandle(DeviceHandle);

continue;

}

}catch (...) { continue;

}

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