SPRUHZ7K August 2015 – April 2024 AM5706 , AM5708 , AM5716 , AM5718 , AM5718-HIREL
USB devices use descriptors to report their attributes. A descriptor is a data structure with a defined format. Each descriptor begins with a byte-wide field that contains the total number of bytes in the descriptor followed by a byte-wide field that identifies the descriptor type. Using descriptors allows concise storage of the attributes of individual configurations so that each configuration can reuse descriptors or portions of descriptors from other configurations that have the same characteristics. Where appropriate, descriptors contain references to string descriptors. String descriptors contain displayable, human-readable description information. These descriptor details can be used for tool development or debugging:
A device descriptor contains general information about a USB device, including global information that applies to the device and all device configurations. A USB device has only one device descriptor. A device-qualifier descriptor is required because the ROM code uses the HS feature of the USB core. Table 33-23 lists the device descriptors.
Field | Value | Description |
---|---|---|
bLength | 0x12 | Size of this descriptor in bytes |
bDescriptorType | 0x01 | Device descriptor type |
bcdUSB | 0x0210 | USB specification release number in binary coded decimal (BCD) format |
bDeviceClass | Vendor-specific (0xFF) | Class code |
bDeviceSubClass | Vendor-specific (0xFF) | Subclass code |
bDeviceProtocol | Vendor-specific (0xFF) | Protocol code |
bMaxPacketSize0 | 0x40 | Maximum packet size for endpoint 0 |
idVendor | 0x0451 | Vendor ID (Texas Instruments), TI default value |
idProduct | 0xD014 | Product ID, TI default value |
bcdDevice | 0x0000 | Device release number |
iManufacturer | See Section 33.3.5.3.5. | Index of string descriptor describing manufacturer |
iProduct | See Section 33.3.5.3.5. | Index of string descriptor describing product |
iSerialNumber | See Section 33.3.5.3.5. | Index of string descriptor describing device serial number |
bNumConfigurations | 0x01 | Number of possible configurations |