MDK-ARM Keil, MDK-ARM Datasheet - Page 117

• 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
117
Device Configuration
When a device is first connected to the USB host, its signaling speed is
determined. It has Endpoint 0 configured to accept a Control pipe. In addition,
every new device that is plugged onto the network is assigned address 0. This
way the USB host knows which bit rate to use. It has one control channel
available at address 0 Endpoint 0. This Control pipe is then used by the host-PC
to determine the capabilities of the new device and to add it to the network. This
process is called “Enumeration”. Therefore, in addition to configuring the USB
peripheral within the microcontroller, you need to provide some firmware that
responds to the USB host enumeration requests. The data requested by the host
is held in a hierarchy of descriptors. The device descriptors are arrays of data,
which fully describe the USB device’s communication interface.
The descriptors are simply arrays of data, which must be transferred to the host in
response to enumeration requests. As you can see from the picture above, it is
possible to build complex device configurations. This is because the USB
network has been designed to be as flexible and as future-proof as possible.
However, the minimum number of descriptors required is a device descriptor,
configuration descriptor, interface descriptor, and three Endpoint descriptors (one
control, one IN and one OUT pipe).