MDK-ARM Keil, MDK-ARM Datasheet - Page 129

• Manufacturer Part Number: MDK-ARM
• Description: KIT REALVIEW MCU DEVELOPMENT
• Manufacturer: Keil
• Type: Compiler and IDEr

Specifications of MDK-ARM

• For Use With/related Products: ARM MCUs
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Getting Started: Building Applications with RL-ARM
129
used to define and test an HID descriptor. Here we examine the basic structure
of the HID report descriptor and make modifications to get useful applications.
The Report descriptor consists of a series of items. Each item begins with an
item TAG that describes the item’s function, scope, and size.
Five main tags define
the Report descriptor
structure. The first
three define the input
data structure, output
data structure, and
configuration features.
Another two tags, the
collection tag and the
end-collection tag,
group together the
associated input,
output, and feature items as shown in the picture. This
allows the Windows HID driver to communicate with the
USB device.
The simplest devices have one collection that defines the
input and output data structures. A more complex device
may consist of several such collections. To construct a
Report descriptor, we can use the file
. This file
hid.h
contains a series of macros that define the Report
descriptor tags. To understand how these are used, we will examine the Report
descriptor used in the basic HID example, which may be found in the
directory.
C:\KEIL\ARM\BOARDS
In this example, the host sends one byte to the device to control the state of eight
LEDs. The device then sends one byte to the host. The first three bits report the
state of three general purpose input/output (GPIO) pins configured as inputs.
The remaining five bits are unused.
HID_UsagePageVendor (0x00),
HID_Usage (0x01),
The Report descriptor begins by defining the device’s function through a usage
page. The HID specification defines standard application profile pages for
common functions. These are defined in the HID usage table document, which
can be downloaded from the USB Implementers’ Forum.