HID Sensor Usage Tables - USB.org

99 HID Sensor Usages
unsigned long pid;
} PROPERTYKEY;
Actual data can be described in a single structure called a VARIANT type, as follows:
#define VARIANT_BOOL unsigned char // use LSb of byte
#define HIDFLOAT16 unsigned short // 16-bit mantissa
#define HIDFLOAT32 unsigned long // 32-bit mantissa
typedef union _flattened_variant_u {
VARIANT_BOOL boolVal;
unsigned char bVal;
unsigned short uiVal;
short iVal;
unsigned long ulVal;
long lVal;
unsigned long long uhVal;
long long hVal;
float fltVal;
double dblVal;
wchar_t wszVal[ WIDE_STRING_SIZE_MAX ];
char szVal[ STRING_SIZE_MAX ];
FLAT_VARIANTVEC vecVal;
HIDFLOAT16 f16Val;
HIDFLOAT32 f32Val;
GUID guidVal;
} FLAT_VARIANT_UNION;
Special mention needs to be made about the VARIANTVEC type, which is used to store compex “struct”
data types, such as used for:
HID_USAGE_SENSOR_PROPERTY_RESPONSE_CURVE
HID_USAGE_SENSOR_DATA_ORIENTATION_ROTATION_MATRIX
HID_USAGE_SENSOR_DATA_ORIENTATION_QUATERNION
HID_USAGE_SENSOR_DATA_GENERIC_GUID_OR_PROPERTYKEY
Any other vendor-opaque data
The definition of the VARIANTVEC structure is:
typedef struct _flattened_variant_vector_t {
// the number valid BYTEs in paubElems
unsigned long caubElems;
// array of BYTEs holding the data
unsigned char paubElems[ VECTOR_BYTE_SIZE_MAX ];
} FLAT_VARIANTVEC;
The struct data is type-cast over the top of the paubElems field, and the length (in bytes) of the struct is
stored in the caubElems field.
Here is an example for SENSOR_DATA_TYPE_LIGHT_RESPONSE_CURVE, which MSDN says each
value element must be 32-bits (size of VT_UI4), allowing 14 of them to fit into a USB Interrupt Packet:
struct _light_response_curve {
// LCD Display should be set to this percentage when...
int DisplayBrightnessPercent : 8; // 0% to 100%
// ...Illuminance Lux up to 64K is at this value
int CorrespondingLuxValue: 24; // 0 to 100,000 Lux
} LightResponseCurve[ 14 ];
FLAT_VARIANT_UNION fvu;
fvu.vecVal.caubElems = (unsigned long)sizeof(LightResponseCurve);
struct _light_response_curve *pLRC = (struct _light_response_curve *)fvu.vecVal.paubElems;
pLRC->DisplayBrightnessPercent = 10;
pLRC->CorrespondingLuxValue = 10;
pLRC++;
pLRC->DisplayBrightnessPercent = 50;
pLRC->CorrespondingLuxValue = 100;
pLRC++;
pLRC->DisplayBrightnessPercent = 75;
pLRC->CorrespondingLuxValue = 10000;
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