Comtrol eCos - Manual (Page 684)

USB Enumeration Data
};
int
main(int argc, char** argv)
{
usbs_sa11x0_ep0.enumeration_data = &usb_enum_data;
...
usbs_start(&usbs_sa11x0_ep0);
...
}
For most applications the enumeration data will be static, although the usbs_enumeration_data structure can be
filled in at run-time if necessary. Full details of the enumeration data can be found in the Universal Serial Bus
specification obtainable from the USB Implementers Forum web site (http://www.usb.org/), although the meaning
of most fields is fairly obvious. The various data structures and utility macros are defined in the header files
cyg/io/usb/usb.h and cyg/io/usb/usbs.h . Note that the example code below makes use of the gcc labelled
element extension.
usb_device_descriptor
The main information about a USB peripheral comes from a single usb_device_descriptor structure, which is
embedded in the usbs_enumeration_data structure. A typical example might look like this:
const usbs_enumeration_data usb_enum_data = {
{
length: USB_DEVICE_DESCRIPTOR_LENGTH,
type: USB_DEVICE_DESCRIPTOR_TYPE,
usb_spec_lo: USB_DEVICE_DESCRIPTOR_USB11_LO,
usb_spec_hi: USB_DEVICE_DESCRIPTOR_USB11_HI,
device_class: USB_DEVICE_DESCRIPTOR_CLASS_VENDOR,
device_subclass: USB_DEVICE_DESCRIPTOR_SUBCLASS_VENDOR,
device_protocol: USB_DEVICE_DESCRIPTOR_PROTOCOL_VENDOR,
max_packet_size: 8,
vendor_lo: 0x42,
vendor_hi: 0x42,
product_lo: 0x42,
product_hi: 0x42,
device_lo: 0x00,
device_hi: 0x01,
manufacturer_str: 1,
product_str: 2,
serial_number_str: 0,
number_configurations: 1
},
...
};
The length and type fields are specified by the USB standard. The usb_spec_lo and usb_spec_hi fields
identify the particular revision of the standard that the peripheral implements, for example revision 1.1.
The device class, subclass, and protocol fields are used by generic host-side USB software to determine which host-
side device driver should be loaded to interact with the peripheral. A number of standard classes are defined, for
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