Microscan MS-4 User Manual page 72

USB HID Interface
Keyboard Report Format
Size: 9 bytes, fixed-length.
Structure: REPORT ID (1) MODIFIER (1) RESERVED (1) KEYCODES (6)
Values in parentheses indicate the size, in bytes, of the field.
Important: The host application does not need to understand and process Keyboard
Reports. This task belongs to the host operating system. Keycodes are passed to the host
application as if a user were typing keyboard text. The host application must be the active
application in order to receive keystrokes.
Keyboard Reports protocol requires that two reports be sent for every keystroke. The first
report indicates which key is pressed. The second report indicates "no key pressed", with
all keycodes NUL (0x00) to indicate that all keys have been released. In the case of the
MS-4 Imager, each byte output is equivalent to a keystroke, with a "key pressed" report
and a "no key pressed" report. For this reason, data rates are much slower when using
Keyboard Reports.
Field Descriptions
REPORT ID
Size: 1 byte
Value: 0x02
Note: Report ID is the method employed by USB HID to allow multiple report formats to be
sent and received from the same interface.
MODIFIER
Size: 1 byte
Value: 0x00 to 0xFF
Note: Modifier is an 8 bit field, corresponding to the state of the modifier keys at the time
the keycode field was generated.
Bit Key
0 LEFT CTRL
1 LEFT SHIFT
2 LEFT ALT
3 LEFT GUI
4 RIGHT CTRL
5 RIGHT SHIFT
6 RIGHT ALT
7 RIGHT GUI
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MS-4 Imager User's Manual