MM7150
DS00001888B-page 8 2015 - 2016 Microchip Technology Inc.
3.0 MM7150 HID FUNCTIONS
The MM7150 responds to the standard HID protocol for sensors when used over I
2
C, defined in References [1] and [2].
The hierarchy of descriptors used in the HID protocol is as follows:
The following sections described the descriptors required for communicating with the MM7150:
3.1 HID Descriptor
3.2 Report Descriptors
Report descriptors are composed of pieces of information. Each piece of information is called an Item.
The HID class driver contains a parser used to analyze items found in the Report descriptor. The parser extracts infor-
mation from the descriptor in a linear fashion.
The parser collects the state of each known item as it walks through the descriptor, and stores them in an item state
table. The item state table contains the state of individual items. From the parser's point of view, a HID class device looks
like the following.
TABLE 3-1: HID DESCRIPTOR FORMAT (I
2
C)
Field Description Size Value
wHIDDescLength Length of HID Descriptor UINT 16 0x001E
bcdVersion Version compliance. Compliant with Version 1.00 UINT 16 0x0100
wReportDescLength Report Descriptor Length (3213 bytes) UINT 16 0x0C8D
wReportDescRegister Identifier to read Report Descriptor UINT 16 0x0002
wInputRegister Identifier to read Input Report UINT 16 0x0003
wMaxInputLength Input Report is 13 Bytes + 2 Bytes length field UINT 16 0x000D
wOutputRegistert Identifier to read Output Report UINT 16 0x0000
wMaxOutputLength No Output Report UINT 16 0x0000
wCommandRegister Identifier for Command Register UINT 16 0x0005
wDataRegister Identifier for Data Register UINT 16 0x0006
wVendorID Vendor ID UINT 16 0x04D8
wProductID Product ID UINT 16 0x0F01
wVersionID Version UINT 16 0x7150
RESERVED Reserved UINT 32 0x0
