HID Sensor Usage Tables - USB.org

79 HID Sensor Usages
A value is identified as an unsigned integer when the ReportSize field = 8, 16 or 32 while the
Units Exponent value = 0. In this section, this is expressed as HID_REPORT_SIZE(8),
HID_REPORT_SIZE(16), or HID_REPORT_SIZE(32) respectively. Logical Minimum and
Logical Maximum must both be positive values. Units can be specified or remain unspecified.
Units Exponent must be = 0.
Signed Integer
Float Value
A value is identified as an signed integer when the ReportSize field = 8, 16 or 32 while the Units
Exponent value = 0. In this section, this is expressed as HID_REPORT_SIZE(8),
HID_REPORT_SIZE(16), or HID_REPORT_SIZE(32) respectively. Logical Minimum must be a
negative value and Logical Maximum must be a positive value. Units can be specified or remain
unspecified. Units Exponent must be = 0.
Essentially, a float is expressed as a combination of a mantissa carried in the value field, and the
exponent expressed as power of 10 carried in the Unit Exponent field. A value is identified as a
float value when the ReportSize field = 16 or 32 while the Units Exponent value is not 0. In this
section, this is expressed as HID_REPORT_SIZE(16) or HID_REPORT_SIZE(32) respectively.
Logical Minimum must be a negative value and Logical Maximum must be a positive value. Units
can be specified or remain unspecified. Units Exponent must not be = 0. The Unit Exponent field
is translated into powers of 10 as specified by the following table.
Value Exponent Power of Ten
0x00 1x10E0 1
0x01 1X10E1 10
0x02 1x10E2 100
0x03 1x10E3 1 000
0x04 1x10E4 10 000
0x05 1x10E5 100 000
0x06 1x10E6 1 000 000
0x07 1x10E7 10 000 000
0x08 1x10E-8 0.00 000 001
0x09 1x10E-7 0.0 000 001
0x0A 1x10E-6 0.000 001
0x0B 1x10E-5 0.00 001
0x0C 1x10E-4 0.0 001
0x0D 1x10E-3 0.001
0x0E 1x10E-2 0.01
0x0F 1x10E-1 0.1
Table 18. HID Unit Exponent encoding and meanings
These Unit Exponent field usages are not unique to this specification, but are the same as the standard HID
definitions.