SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
The device-qualifier descriptor contains information about a HS-capable device that changes if the device operates at its other speed. This descriptor is retrieved by the host using the GetDescriptor() request (standard device request). Table 32-24 lists the device-qualifier descriptors.
Field | Value | Description |
---|---|---|
bLength | 0x0A | Size of this descriptor in bytes |
bDescriptorType | 0x06 | Device-qualifier descriptor type |
bcdUSB | 0x0210 | USB specification release number in BCD |
bDeviceClass | 0xFF | Class code |
bDeviceSubClass | 0xFF | Subclass code |
bDeviceProtocol | 0xFF | Protocol code |
bMaxPacketSize0 | 0x40 | Maximum packet size for endpoint 0 |
bNumConfigurations | 0x01 | Number of possible configurations |
bReserved | 0x00 | Reserved for future use |
This descriptor gives information about a specific device configuration. It describes the number of interfaces supported by the configuration (see Table 32-25).
Field | Value | Description |
---|---|---|
bLength | 0x09 | Size of this descriptor in bytes |
bDescriptorType | 0x02 | Configuration descriptor type |
wTotalLength | – | Combined length of all descriptors |
bNumInterfaces | 0x01 | Number of interfaces supported |
bConfigurationValue | 0x01 | Value to use as an argument for the SetConfiguration() request |
iConfiguration | Index | Index of string descriptor describing this configuration |
bmAttributes | 0xC0 | Power setting and remote wakeup |
bMaxPower | 0x32 | Maximum power consumption of the USB device |
This descriptor describes the configuration of a HS-capable device if it operates at its other possible speed (see Table 32-26).
Field | Value | Description |
---|---|---|
bLength | 0x09 | Size of this descriptor in bytes |
bDescriptorType | 0x07 | Other speed configuration descriptor type |
wTotalLength | – | Combined length of all descriptors |
bNumInterfaces | 0x01 | Number of interfaces supported |
bConfigurationValue | 0x01 | Value to use as an argument for the SetConfiguration() request |
iConfiguration | Index | Index of string descriptor describing this configuration |
bmAttributes | 0xC0 | Power setting and remote wakeup |
bMaxPower | 0x32 | Maximum power consumption of the USB device |
This descriptor describes a specific interface in a configuration (see Table 32-27).
Field | Value | Description |
---|---|---|
bLength | 0x09 | Size of this descriptor in bytes |
bDescriptorType | 0x04 | Interface descriptor type |
bInterfaceNumber | 0x00 | Number of this descriptor |
bAlternateSetting | 0x00 | Value to select the alternate setting |
bNumEndpoints | 0x02 | Number of endpoints used for this interface |
bInterfaceClass | 0xFF | Class code |
bInterfaceSubClass | 0xFF | Subclass code |
bInterfaceProtocol | 0xFF | Protocol code |
iInterface | Index | Index of string descriptor describing this interface |
Each endpoint used for an interface has its own descriptor. This descriptor contains information required by the host to determine the bandwidth requirements of each endpoint. This descriptor is returned as part of the GetDescriptor(Configuration) request (see Table 32-28 and Table 32-29).
Field | Value | Description |
---|---|---|
bLength | 0x07 | Size of this descriptor in bytes |
bDescriptorType | 0x05 | Endpoint descriptor type |
bEndpointAddress | 0x81 (1 IN) | Address of the endpoint on the USB device |
bmAttributes | 0x02 (Bulk) | Type of transfer |
wMaxPacketSize | See (1). | Number of endpoints used for this interface |
bInterval | 0x00 | Maximum NAK rate |
Field | Value | Description |
---|---|---|
bLength | 0x07 | Size of this descriptor in bytes |
bDescriptorType | 0x05 | Endpoint descriptor type |
bEndpointAddress | 0x01 (1 OUT) | Address of the endpoint on the USB device |
bmAttributes | 0x02 (Bulk) | Type of transfer |
wMaxPacketSize | See (1). | Number of endpoints used for this interface |
bInterval | 0x00 | Maximum NAK rate |
String descriptors use UNICODE encoding. The strings in a USB device can support multiple languages. When requesting a string descriptor, the requester specifies the desired language using a 16-bit language ID (LANGID) defined by the USB interface. String index 0 for all languages returns a string descriptor that contains an array of 2-byte LANGID codes supported by the device.
For the description of the different string descriptors, see:
Field | Value | Description |
---|---|---|
bLength | 0x04 | Size of this descriptor in bytes |
bDescriptorType | 0x03 | String descriptor type |
wLangId | 0x0409 (US English) | Language ID code |
Field | Value | Description |
---|---|---|
bLength | 0x24 | Size of this descriptor in bytes |
bDescriptorType | 0x03 | String descriptor type |
bString | Texas Instruments | Manufacturer string |
Field | Value | Description |
---|---|---|
bLength | 0x12 | Size of this descriptor in bytes |
bDescriptorType | 0x03 | String descriptor type |
bString | <string> | Product string |
Field | Value | Description |
---|---|---|
bLength | 0x08 | Size of this descriptor in bytes |
bDescriptorType | 0x03 | String descriptor type |
bString | pbc | Configuration string |
Field | Value | Description |
---|---|---|
bLength | 0x08 | Size of this descriptor in bytes |
bDescriptorType | 0x03 | String descriptor type |
bString | pbi | Interface string |