AN249 Silicon_Laboratories, AN249 Datasheet - Page 13

• Manufacturer Part Number: AN249
• Description: Human Interface Device Tutorial
• Manufacturer: Silicon_Laboratories

5.4.2. Configuration Descriptor
After the host retrieves the Device Descriptor, it can request other descriptors including the Configuration
Descriptor. The following is the firmware template’s Configuration Descriptor:
{
}
This defines the length of the Configuration Descriptor. This is a standard length and should be common to all HID
devices.
0x02 is the constant one-byte designator for Configuration descriptors.
This two-byte item defines the length of this descriptor and all of the other descriptors associated with this
configuration. The length of this example is calculated by adding the length of the Configuration Descriptor, the
Interface Descriptor, the HID Descriptor, and one Endpoint Descriptor. This two-byte item follows a “little endian”
data format.
This two-byte item defines the length of this descriptor and all of the other descriptors associated with this
configuration. The length of this example is calculated by adding the lengths of the 9-byte Configuration Descriptor,
the 9-byte Interface Descriptor, the 9-byte HID Descriptor, and one 7-byte Endpoint Descriptor. Note that this two-
byte length value follows a "little endian" format, where the value is stored least significant byte first.
This item defines the number of interface settings contained in this configuration.
This item gives this particular configuration a designation of 0x01, which can be used in the standard USB requests
Get_Configuration and Set_Configuration to identify this configuration. This number must be higher than
0.
This item defines the string index for a string that describes this configuration. This example defines no
Configuration String and sets the index to 0x00 to indicate this condition to the host.
This item tells the host whether the device supports USB features such as remote wake-up. Item bits are set or
cleared to describe these conditions. Check the USB specification for a detailed discussion on this item.
This item tells the host how much current the device will require to function properly at this configuration.
0x09,
0x02,
0x0000,
0x01,
0x01,
0x00,
0x80,
0x00
0x09,
0x02,
0x2200,
0x01,
0x01,
0x00,
0x80,
0x00
// Length
// Type
// Totallength
// NumInterfaces
// bConfigurationValue
// iConfiguration
// bmAttributes
// MaxPower (in 2 mA units)
// Length
// Type
// Totallength
// NumInterfaces
// bConfigurationValue
// iConfiguration
// bmAttributes
// MaxPower (in 2 mA units)
Rev. 0.2
AN249
13