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 1/7
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Coding example AN2328
1 Coding example
1.1 Load 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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Coding example AN2328
//Read Attributes from the current device
HIDD_ATTRIBUTES Attributes;
Attributes.Size = sizeof(Attributes);
try {
Result = HidD_GetAttributes (DeviceHandle,&Attributes);
if (!Result)
{
CloseHandle(DeviceHandle);
continue;
}
} catch (...) {
continue;
}
// All information obtained
// Attributes.VendorID
// Attributes.ProductID
// detailData.DevicePath <- Remember for future use
// easy example can be:
if ((Attributes.VendorID == YOUR_VENDOR_ID) &&
(Attributes.ProductID == YOUR_PRODUCT_ID))
strcpy(your_devicePath, detailData.DevicePath);
} //end of while
1.3 Open device
ReadHandle = CreateFile (your_devicePath,
GENERIC_READ|GENERIC_WRITE,
FILE_SHARE_READ|FILE_SHARE_WRITE,
(LPSECURITY_ATTRIBUTES)NULL,
OPEN_EXISTING,
0,
NULL);
1.4 Read device
DWORD BytesRead = 0;
char Report[INPUT_REPORT_SIZE];
bool Result;
memset(&Report, 0, INPUT_REPORT_SIZE);
Result = ReadFile (ReadHandle,Report,sizeof(Report),&BytesRead,NULL);
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AN2328 Conclusion
2 Conclusion
This way of accessing HID devices is used in the MEMS USB Reader software and tested.
Additional reference material on this subject can be found in reference [1].
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References AN2328
3 References
[1] Jan Axelson, USB COMPLETE, Lakeview Research LLC, Madison, USA, 2001,
ISBN: 0-9650819-5-8
[2] USB specification 2.0, www.usb.org
[3] STMicroelectronics, www.st.com
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AN2328
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