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NAME="USBS-ENUM">USB Enumeration Data</H1
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NAME="USBS-ENUM">USB Enumeration Data</H1
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><DIV
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><DIV
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CLASS="REFNAMEDIV"
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CLASS="REFNAMEDIV"
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><A
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><A
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NAME="AEN16105"
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NAME="AEN16105"
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></A
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></A
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><H2
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><H2
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>Name</H2
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>Name</H2
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>Enumeration Data -- The USB enumeration data structures</DIV
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>Enumeration Data -- The USB enumeration data structures</DIV
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><DIV
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><DIV
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CLASS="REFSYNOPSISDIV"
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CLASS="REFSYNOPSISDIV"
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><A
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><A
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NAME="AEN16108"><H2
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NAME="AEN16108"><H2
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>Synopsis</H2
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>Synopsis</H2
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><TABLE
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><PRE
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><PRE
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CLASS="SYNOPSIS"
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CLASS="SYNOPSIS"
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>#include <cyg/io/usb/usb.h>
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>#include <cyg/io/usb/usb.h>
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#include <cyg/io/usb/usbs.h>
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#include <cyg/io/usb/usbs.h>
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|
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typedef struct usb_device_descriptor {
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typedef struct usb_device_descriptor {
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…
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…
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} usb_device_descriptor __attribute__((packed));
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} usb_device_descriptor __attribute__((packed));
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|
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typedef struct usb_configuration_descriptor {
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typedef struct usb_configuration_descriptor {
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…
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…
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} usb_configuration_descriptor __attribute__((packed));
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} usb_configuration_descriptor __attribute__((packed));
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|
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typedef struct usb_interface_descriptor {
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typedef struct usb_interface_descriptor {
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…
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…
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} usb_interface_descriptor __attribute__((packed));
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} usb_interface_descriptor __attribute__((packed));
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|
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typedef struct usb_endpoint_descriptor {
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typedef struct usb_endpoint_descriptor {
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…
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…
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} usb_endpoint_descriptor;
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} usb_endpoint_descriptor;
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|
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typedef struct usbs_enumeration_data {
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typedef struct usbs_enumeration_data {
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usb_device_descriptor device;
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usb_device_descriptor device;
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int total_number_interfaces;
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int total_number_interfaces;
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int total_number_endpoints;
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int total_number_endpoints;
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int total_number_strings;
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int total_number_strings;
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const usb_configuration_descriptor* configurations;
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const usb_configuration_descriptor* configurations;
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const usb_interface_descriptor* interfaces;
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const usb_interface_descriptor* interfaces;
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const usb_endpoint_descriptor* endpoints;
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const usb_endpoint_descriptor* endpoints;
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const unsigned char** strings;
|
const unsigned char** strings;
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} usbs_enumeration_data;</PRE
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} usbs_enumeration_data;</PRE
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></TD
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></TD
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></TR
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></TR
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></TABLE
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></TABLE
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></DIV
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></DIV
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><DIV
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><DIV
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CLASS="REFSECT1"
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CLASS="REFSECT1"
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><A
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><A
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NAME="AEN16110"
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NAME="AEN16110"
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></A
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></A
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><H2
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><H2
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>USB Enumeration Data</H2
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>USB Enumeration Data</H2
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><P
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><P
|
>When a USB host detects that a peripheral has been plugged in or
|
>When a USB host detects that a peripheral has been plugged in or
|
powered up, one of the first steps is to ask the peripheral to
|
powered up, one of the first steps is to ask the peripheral to
|
describe itself by supplying enumeration data. Some of this data
|
describe itself by supplying enumeration data. Some of this data
|
depends on the class of peripheral. Other fields are vendor-specific.
|
depends on the class of peripheral. Other fields are vendor-specific.
|
There is also a dependency on the hardware, specifically which
|
There is also a dependency on the hardware, specifically which
|
endpoints are available should be used. In general it is not possible
|
endpoints are available should be used. In general it is not possible
|
for generic code to provide this information, so it is the
|
for generic code to provide this information, so it is the
|
responsibility of application code to provide a suitable
|
responsibility of application code to provide a suitable
|
<SPAN
|
<SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usbs_enumeration_data</SPAN
|
>usbs_enumeration_data</SPAN
|
> data structure and
|
> data structure and
|
install it in the endpoint 0 data structure during initialization.
|
install it in the endpoint 0 data structure during initialization.
|
This must happen before the USB device is enabled by a call to
|
This must happen before the USB device is enabled by a call to
|
<TT
|
<TT
|
CLASS="FUNCTION"
|
CLASS="FUNCTION"
|
>usbs_start</TT
|
>usbs_start</TT
|
>, for example:</P
|
>, for example:</P
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><TABLE
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BORDER="5"
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WIDTH="70%"
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WIDTH="70%"
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><TR
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><TR
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><TD
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><TD
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><PRE
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><PRE
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CLASS="PROGRAMLISTING"
|
CLASS="PROGRAMLISTING"
|
>const usbs_enumeration_data usb_enum_data = {
|
>const usbs_enumeration_data usb_enum_data = {
|
…
|
…
|
};
|
};
|
|
|
int
|
int
|
main(int argc, char** argv)
|
main(int argc, char** argv)
|
{
|
{
|
usbs_sa11x0_ep0.enumeration_data = &usb_enum_data;
|
usbs_sa11x0_ep0.enumeration_data = &usb_enum_data;
|
…
|
…
|
usbs_start(&usbs_sa11x0_ep0);
|
usbs_start(&usbs_sa11x0_ep0);
|
…
|
…
|
}</PRE
|
}</PRE
|
></TD
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></TD
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></TR
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></TR
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></TABLE
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></TABLE
|
><P
|
><P
|
>For most applications the enumeration data will be static, although
|
>For most applications the enumeration data will be static, although
|
the <SPAN
|
the <SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usbs_enumeration_data</SPAN
|
>usbs_enumeration_data</SPAN
|
> structure can be
|
> structure can be
|
filled in at run-time if necessary. Full details of the enumeration
|
filled in at run-time if necessary. Full details of the enumeration
|
data can be found in the Universal Serial Bus specification obtainable
|
data can be found in the Universal Serial Bus specification obtainable
|
from the <A
|
from the <A
|
HREF="http://www.usb.org/"
|
HREF="http://www.usb.org/"
|
TARGET="_top"
|
TARGET="_top"
|
>USB Implementers Forum web
|
>USB Implementers Forum web
|
site</A
|
site</A
|
>, although the meaning of most fields is fairly obvious.
|
>, although the meaning of most fields is fairly obvious.
|
The various data structures and utility macros are defined in the
|
The various data structures and utility macros are defined in the
|
header files <TT
|
header files <TT
|
CLASS="FILENAME"
|
CLASS="FILENAME"
|
>cyg/io/usb/usb.h</TT
|
>cyg/io/usb/usb.h</TT
|
>
|
>
|
and <TT
|
and <TT
|
CLASS="FILENAME"
|
CLASS="FILENAME"
|
>cyg/io/usb/usbs.h</TT
|
>cyg/io/usb/usbs.h</TT
|
>. Note
|
>. Note
|
that the example code below makes use of the gcc labelled element
|
that the example code below makes use of the gcc labelled element
|
extension.</P
|
extension.</P
|
><DIV
|
><DIV
|
CLASS="REFSECT2"
|
CLASS="REFSECT2"
|
><A
|
><A
|
NAME="AEN16121"
|
NAME="AEN16121"
|
></A
|
></A
|
><H3
|
><H3
|
><SPAN
|
><SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usb_device_descriptor</SPAN
|
>usb_device_descriptor</SPAN
|
></H3
|
></H3
|
><P
|
><P
|
>The main information about a USB peripheral comes from a single
|
>The main information about a USB peripheral comes from a single
|
<SPAN
|
<SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usb_device_descriptor</SPAN
|
>usb_device_descriptor</SPAN
|
> structure, which is
|
> structure, which is
|
embedded in the <SPAN
|
embedded in the <SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usbs_enumeration_data</SPAN
|
>usbs_enumeration_data</SPAN
|
>
|
>
|
structure. A typical example might look like this:</P
|
structure. A typical example might look like this:</P
|
><TABLE
|
><TABLE
|
BORDER="5"
|
BORDER="5"
|
BGCOLOR="#E0E0F0"
|
BGCOLOR="#E0E0F0"
|
WIDTH="70%"
|
WIDTH="70%"
|
><TR
|
><TR
|
><TD
|
><TD
|
><PRE
|
><PRE
|
CLASS="PROGRAMLISTING"
|
CLASS="PROGRAMLISTING"
|
>const usbs_enumeration_data usb_enum_data = {
|
>const usbs_enumeration_data usb_enum_data = {
|
{
|
{
|
length: USB_DEVICE_DESCRIPTOR_LENGTH,
|
length: USB_DEVICE_DESCRIPTOR_LENGTH,
|
type: USB_DEVICE_DESCRIPTOR_TYPE,
|
type: USB_DEVICE_DESCRIPTOR_TYPE,
|
usb_spec_lo: USB_DEVICE_DESCRIPTOR_USB11_LO,
|
usb_spec_lo: USB_DEVICE_DESCRIPTOR_USB11_LO,
|
usb_spec_hi: USB_DEVICE_DESCRIPTOR_USB11_HI,
|
usb_spec_hi: USB_DEVICE_DESCRIPTOR_USB11_HI,
|
device_class: USB_DEVICE_DESCRIPTOR_CLASS_VENDOR,
|
device_class: USB_DEVICE_DESCRIPTOR_CLASS_VENDOR,
|
device_subclass: USB_DEVICE_DESCRIPTOR_SUBCLASS_VENDOR,
|
device_subclass: USB_DEVICE_DESCRIPTOR_SUBCLASS_VENDOR,
|
device_protocol: USB_DEVICE_DESCRIPTOR_PROTOCOL_VENDOR,
|
device_protocol: USB_DEVICE_DESCRIPTOR_PROTOCOL_VENDOR,
|
max_packet_size: 8,
|
max_packet_size: 8,
|
vendor_lo: 0x42,
|
vendor_lo: 0x42,
|
vendor_hi: 0x42,
|
vendor_hi: 0x42,
|
product_lo: 0x42,
|
product_lo: 0x42,
|
product_hi: 0x42,
|
product_hi: 0x42,
|
device_lo: 0x00,
|
device_lo: 0x00,
|
device_hi: 0x01,
|
device_hi: 0x01,
|
manufacturer_str: 1,
|
manufacturer_str: 1,
|
product_str: 2,
|
product_str: 2,
|
serial_number_str: 0,
|
serial_number_str: 0,
|
number_configurations: 1
|
number_configurations: 1
|
},
|
},
|
…
|
…
|
};</PRE
|
};</PRE
|
></TD
|
></TD
|
></TR
|
></TR
|
></TABLE
|
></TABLE
|
><P
|
><P
|
>The length and type fields are specified by the USB standard. The
|
>The length and type fields are specified by the USB standard. The
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>usb_spec_lo</I
|
>usb_spec_lo</I
|
></TT
|
></TT
|
> and
|
> and
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>usb_spec_hi</I
|
>usb_spec_hi</I
|
></TT
|
></TT
|
> fields identify the particular
|
> fields identify the particular
|
revision of the standard that the peripheral implements, for example
|
revision of the standard that the peripheral implements, for example
|
revision 1.1.</P
|
revision 1.1.</P
|
><P
|
><P
|
>The device class, subclass, and protocol fields are used by generic
|
>The device class, subclass, and protocol fields are used by generic
|
host-side USB software to determine which host-side device driver
|
host-side USB software to determine which host-side device driver
|
should be loaded to interact with the peripheral. A number of standard
|
should be loaded to interact with the peripheral. A number of standard
|
classes are defined, for example mass-storage devices and
|
classes are defined, for example mass-storage devices and
|
human-interface devices. If a peripheral implements one of the
|
human-interface devices. If a peripheral implements one of the
|
standard classes then a standard existing host-side device driver may
|
standard classes then a standard existing host-side device driver may
|
exist, eliminating the need to write a custom driver. The value
|
exist, eliminating the need to write a custom driver. The value
|
<TT
|
<TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>0xFF</TT
|
>0xFF</TT
|
> (<TT
|
> (<TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>VENDOR</TT
|
>VENDOR</TT
|
>) is reserved for
|
>) is reserved for
|
peripherals that implement a vendor-specific protocol rather than a
|
peripherals that implement a vendor-specific protocol rather than a
|
standard one. Such peripherals will require a custom host-side device
|
standard one. Such peripherals will require a custom host-side device
|
driver. The value <TT
|
driver. The value <TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>0x00</TT
|
>0x00</TT
|
>
|
>
|
(<TT
|
(<TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>INTERFACE</TT
|
>INTERFACE</TT
|
>) is reserved and indicates that the
|
>) is reserved and indicates that the
|
protocol used by the peripheral is defined at the interface level
|
protocol used by the peripheral is defined at the interface level
|
rather than for the peripheral as a whole.</P
|
rather than for the peripheral as a whole.</P
|
><P
|
><P
|
>The <TT
|
>The <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>max_package_size</I
|
>max_package_size</I
|
></TT
|
></TT
|
> field specifies the
|
> field specifies the
|
maximum length of a control message. There is a lower bound of eight
|
maximum length of a control message. There is a lower bound of eight
|
bytes, and typical hardware will not support anything larger because
|
bytes, and typical hardware will not support anything larger because
|
control messages are usually small and not performance-critical.</P
|
control messages are usually small and not performance-critical.</P
|
><P
|
><P
|
>The <TT
|
>The <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>vendor_lo</I
|
>vendor_lo</I
|
></TT
|
></TT
|
> and
|
> and
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>vendor_hi</I
|
>vendor_hi</I
|
></TT
|
></TT
|
> fields specify a vendor id, which
|
> fields specify a vendor id, which
|
must be obtained from the USB Implementor's Forum. The numbers used in
|
must be obtained from the USB Implementor's Forum. The numbers used in
|
the code fragment above are examples only and must not be used in real
|
the code fragment above are examples only and must not be used in real
|
USB peripherals. The product identifier is determined by the vendor,
|
USB peripherals. The product identifier is determined by the vendor,
|
and different USB peripherals should use different identifiers. The
|
and different USB peripherals should use different identifiers. The
|
device identifier field should indicate a release number in
|
device identifier field should indicate a release number in
|
binary-coded decimal.</P
|
binary-coded decimal.</P
|
><P
|
><P
|
>The above fields are all numerical in nature. A USB peripheral can
|
>The above fields are all numerical in nature. A USB peripheral can
|
also provide a number of strings as described <A
|
also provide a number of strings as described <A
|
HREF="usbs-enum.html#AEN16196"
|
HREF="usbs-enum.html#AEN16196"
|
>below</A
|
>below</A
|
>, for example the name of the
|
>, for example the name of the
|
vendor can be provided. The various <TT
|
vendor can be provided. The various <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>_str</I
|
>_str</I
|
></TT
|
></TT
|
>
|
>
|
fields act as indices into an array of strings, with index 0
|
fields act as indices into an array of strings, with index 0
|
indicating that no string is available. </P
|
indicating that no string is available. </P
|
><P
|
><P
|
>A typical USB peripheral involves just a single configuration. However
|
>A typical USB peripheral involves just a single configuration. However
|
more complicated peripherals can support multiple configurations. Only
|
more complicated peripherals can support multiple configurations. Only
|
one configuration will be active at any one time, and the host will
|
one configuration will be active at any one time, and the host will
|
switch between them as appropriate. If a peripheral does involve
|
switch between them as appropriate. If a peripheral does involve
|
multiple configurations then typically it will be the responsibility
|
multiple configurations then typically it will be the responsibility
|
of application code to <A
|
of application code to <A
|
HREF="usbs-control.html#AEN16582"
|
HREF="usbs-control.html#AEN16582"
|
>handle</A
|
>handle</A
|
> the standard
|
> the standard
|
set-configuration control message.</P
|
set-configuration control message.</P
|
></DIV
|
></DIV
|
><DIV
|
><DIV
|
CLASS="REFSECT2"
|
CLASS="REFSECT2"
|
><A
|
><A
|
NAME="AEN16146"
|
NAME="AEN16146"
|
></A
|
></A
|
><H3
|
><H3
|
><SPAN
|
><SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usb_configuration_descriptor</SPAN
|
>usb_configuration_descriptor</SPAN
|
></H3
|
></H3
|
><P
|
><P
|
>A USB peripheral involves at least one and possible several different
|
>A USB peripheral involves at least one and possible several different
|
configurations. The <SPAN
|
configurations. The <SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usbs_enumeration_data</SPAN
|
>usbs_enumeration_data</SPAN
|
>
|
>
|
structure requires a pointer to an array, possibly of length 1, of
|
structure requires a pointer to an array, possibly of length 1, of
|
<SPAN
|
<SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usb_configuration_descriptor</SPAN
|
>usb_configuration_descriptor</SPAN
|
> structures.
|
> structures.
|
Usually a single structure suffices:</P
|
Usually a single structure suffices:</P
|
><TABLE
|
><TABLE
|
BORDER="5"
|
BORDER="5"
|
BGCOLOR="#E0E0F0"
|
BGCOLOR="#E0E0F0"
|
WIDTH="70%"
|
WIDTH="70%"
|
><TR
|
><TR
|
><TD
|
><TD
|
><PRE
|
><PRE
|
CLASS="PROGRAMLISTING"
|
CLASS="PROGRAMLISTING"
|
>const usb_configuration_descriptor usb_configuration = {
|
>const usb_configuration_descriptor usb_configuration = {
|
length: USB_CONFIGURATION_DESCRIPTOR_LENGTH,
|
length: USB_CONFIGURATION_DESCRIPTOR_LENGTH,
|
type: USB_CONFIGURATION_DESCRIPTOR_TYPE,
|
type: USB_CONFIGURATION_DESCRIPTOR_TYPE,
|
total_length_lo: USB_CONFIGURATION_DESCRIPTOR_TOTAL_LENGTH_LO(1, 2),
|
total_length_lo: USB_CONFIGURATION_DESCRIPTOR_TOTAL_LENGTH_LO(1, 2),
|
total_length_hi: USB_CONFIGURATION_DESCRIPTOR_TOTAL_LENGTH_HI(1, 2),
|
total_length_hi: USB_CONFIGURATION_DESCRIPTOR_TOTAL_LENGTH_HI(1, 2),
|
number_interfaces: 1,
|
number_interfaces: 1,
|
configuration_id: 1,
|
configuration_id: 1,
|
configuration_str: 0,
|
configuration_str: 0,
|
attributes: USB_CONFIGURATION_DESCRIPTOR_ATTR_REQUIRED |
|
attributes: USB_CONFIGURATION_DESCRIPTOR_ATTR_REQUIRED |
|
USB_CONFIGURATION_DESCRIPTOR_ATTR_SELF_POWERED,
|
USB_CONFIGURATION_DESCRIPTOR_ATTR_SELF_POWERED,
|
max_power: 50
|
max_power: 50
|
};
|
};
|
|
|
const usbs_enumeration_data usb_enum_data = {
|
const usbs_enumeration_data usb_enum_data = {
|
…
|
…
|
configurations: &usb_configuration,
|
configurations: &usb_configuration,
|
…
|
…
|
};</PRE
|
};</PRE
|
></TD
|
></TD
|
></TR
|
></TR
|
></TABLE
|
></TABLE
|
><P
|
><P
|
>The values for the <TT
|
>The values for the <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>length</I
|
>length</I
|
></TT
|
></TT
|
> and
|
> and
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>type</I
|
>type</I
|
></TT
|
></TT
|
> fields are determined by the standard.
|
> fields are determined by the standard.
|
The <TT
|
The <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>total_length</I
|
>total_length</I
|
></TT
|
></TT
|
> field depends on the
|
> field depends on the
|
number of interfaces and endpoints used by this configuration, and
|
number of interfaces and endpoints used by this configuration, and
|
convenience macros are provided to calculate this: the first argument
|
convenience macros are provided to calculate this: the first argument
|
to the macros specify the number of interfaces, the second the number
|
to the macros specify the number of interfaces, the second the number
|
of endpoints. The <TT
|
of endpoints. The <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>number_interfaces</I
|
>number_interfaces</I
|
></TT
|
></TT
|
> field
|
> field
|
is self-explanatory. If the peripheral involves multiple
|
is self-explanatory. If the peripheral involves multiple
|
configurations then each one must have a unique id, and this will be
|
configurations then each one must have a unique id, and this will be
|
used in the set-configuration control message. The id
|
used in the set-configuration control message. The id
|
<TT
|
<TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>0</TT
|
>0</TT
|
> is reserved, and a set-configuration control
|
> is reserved, and a set-configuration control
|
message that uses this id indicates that the peripheral should be
|
message that uses this id indicates that the peripheral should be
|
inactive. Configurations can have a string description if required.
|
inactive. Configurations can have a string description if required.
|
The <TT
|
The <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>attributes</I
|
>attributes</I
|
></TT
|
></TT
|
> field must have the
|
> field must have the
|
<TT
|
<TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>REQUIRED</TT
|
>REQUIRED</TT
|
> bit set; the
|
> bit set; the
|
<TT
|
<TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>SELF_POWERED</TT
|
>SELF_POWERED</TT
|
> bit informs the host that the
|
> bit informs the host that the
|
peripheral has its own power supply and will not draw any power over
|
peripheral has its own power supply and will not draw any power over
|
the bus, leaving more bus power available to other peripherals; the
|
the bus, leaving more bus power available to other peripherals; the
|
<TT
|
<TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>REMOTE_WAKEUP</TT
|
>REMOTE_WAKEUP</TT
|
> bit is used if the peripheral can
|
> bit is used if the peripheral can
|
interrupt the host when the latter is in power-saving mode. For
|
interrupt the host when the latter is in power-saving mode. For
|
peripherals that are not self-powered, the
|
peripherals that are not self-powered, the
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>max_power</I
|
>max_power</I
|
></TT
|
></TT
|
> field specifies the power
|
> field specifies the power
|
requirements in units of 2mA.</P
|
requirements in units of 2mA.</P
|
></DIV
|
></DIV
|
><DIV
|
><DIV
|
CLASS="REFSECT2"
|
CLASS="REFSECT2"
|
><A
|
><A
|
NAME="AEN16164"
|
NAME="AEN16164"
|
></A
|
></A
|
><H3
|
><H3
|
><SPAN
|
><SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usb_interface_descriptor</SPAN
|
>usb_interface_descriptor</SPAN
|
></H3
|
></H3
|
><P
|
><P
|
>A USB configuration involves one or more interfaces, typically
|
>A USB configuration involves one or more interfaces, typically
|
corresponding to different streams of data. For example, one interface
|
corresponding to different streams of data. For example, one interface
|
might involve video data while another interface is for audio.
|
might involve video data while another interface is for audio.
|
Multiple interfaces in a single configuration will be active at the
|
Multiple interfaces in a single configuration will be active at the
|
same time.</P
|
same time.</P
|
><TABLE
|
><TABLE
|
BORDER="5"
|
BORDER="5"
|
BGCOLOR="#E0E0F0"
|
BGCOLOR="#E0E0F0"
|
WIDTH="70%"
|
WIDTH="70%"
|
><TR
|
><TR
|
><TD
|
><TD
|
><PRE
|
><PRE
|
CLASS="PROGRAMLISTING"
|
CLASS="PROGRAMLISTING"
|
>const usb_interface_descriptor usb_interface = {
|
>const usb_interface_descriptor usb_interface = {
|
length: USB_INTERFACE_DESCRIPTOR_LENGTH,
|
length: USB_INTERFACE_DESCRIPTOR_LENGTH,
|
type: USB_INTERFACE_DESCRIPTOR_TYPE,
|
type: USB_INTERFACE_DESCRIPTOR_TYPE,
|
interface_id: 0,
|
interface_id: 0,
|
alternate_setting: 0,
|
alternate_setting: 0,
|
number_endpoints: 2,
|
number_endpoints: 2,
|
interface_class: USB_INTERFACE_DESCRIPTOR_CLASS_VENDOR,
|
interface_class: USB_INTERFACE_DESCRIPTOR_CLASS_VENDOR,
|
interface_subclass: USB_INTERFACE_DESCRIPTOR_SUBCLASS_VENDOR,
|
interface_subclass: USB_INTERFACE_DESCRIPTOR_SUBCLASS_VENDOR,
|
interface_protocol: USB_INTERFACE_DESCRIPTOR_PROTOCOL_VENDOR,
|
interface_protocol: USB_INTERFACE_DESCRIPTOR_PROTOCOL_VENDOR,
|
interface_str: 0
|
interface_str: 0
|
};
|
};
|
|
|
const usbs_enumeration_data usb_enum_data = {
|
const usbs_enumeration_data usb_enum_data = {
|
…
|
…
|
total_number_interfaces: 1,
|
total_number_interfaces: 1,
|
interfaces: &usb_interface,
|
interfaces: &usb_interface,
|
…
|
…
|
};</PRE
|
};</PRE
|
></TD
|
></TD
|
></TR
|
></TR
|
></TABLE
|
></TABLE
|
><P
|
><P
|
>Again, the <TT
|
>Again, the <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>length</I
|
>length</I
|
></TT
|
></TT
|
> and
|
> and
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>type</I
|
>type</I
|
></TT
|
></TT
|
> fields are specified by the standard.
|
> fields are specified by the standard.
|
Each interface within a configuration requires its own id. However, a
|
Each interface within a configuration requires its own id. However, a
|
given interface may have several alternate settings, in other words
|
given interface may have several alternate settings, in other words
|
entries in the interfaces array with the same id but different
|
entries in the interfaces array with the same id but different
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>alternate_setting</I
|
>alternate_setting</I
|
></TT
|
></TT
|
> fields. For example,
|
> fields. For example,
|
there might be one setting which requires a bandwidth of 100K/s and
|
there might be one setting which requires a bandwidth of 100K/s and
|
another setting that only needs 50K/s. The host can use the standard
|
another setting that only needs 50K/s. The host can use the standard
|
set-interface control message to choose the most appropriate setting.
|
set-interface control message to choose the most appropriate setting.
|
The handling of this request is the responsibility of higher-level
|
The handling of this request is the responsibility of higher-level
|
code, so the application may have to <A
|
code, so the application may have to <A
|
HREF="usbs-control.html#AEN16582"
|
HREF="usbs-control.html#AEN16582"
|
>install</A
|
>install</A
|
> its own handler.</P
|
> its own handler.</P
|
><P
|
><P
|
>The number of endpoints used by an interface is specified in the
|
>The number of endpoints used by an interface is specified in the
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>number_endpoints</I
|
>number_endpoints</I
|
></TT
|
></TT
|
> field. Exact details of
|
> field. Exact details of
|
which endpoints are used is held in a separate array of endpoint
|
which endpoints are used is held in a separate array of endpoint
|
descriptors. The class, subclass and protocol fields are used by
|
descriptors. The class, subclass and protocol fields are used by
|
host-side code to determine which host-side device driver should
|
host-side code to determine which host-side device driver should
|
handle this specific interface. Usually this is determined on a
|
handle this specific interface. Usually this is determined on a
|
per-peripheral basis in the
|
per-peripheral basis in the
|
<SPAN
|
<SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usb_device_descriptor</SPAN
|
>usb_device_descriptor</SPAN
|
> structure, but that can
|
> structure, but that can
|
defer the details to individual interfaces. A per-interface string
|
defer the details to individual interfaces. A per-interface string
|
is allowed as well.</P
|
is allowed as well.</P
|
><P
|
><P
|
>For USB peripherals involving multiple configurations, the array of
|
>For USB peripherals involving multiple configurations, the array of
|
<SPAN
|
<SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usb_interface_descriptor</SPAN
|
>usb_interface_descriptor</SPAN
|
> structures should
|
> structures should
|
first contain all the interfaces for the first configuration, then all
|
first contain all the interfaces for the first configuration, then all
|
the interfaces for the second configuration, and so on.</P
|
the interfaces for the second configuration, and so on.</P
|
></DIV
|
></DIV
|
><DIV
|
><DIV
|
CLASS="REFSECT2"
|
CLASS="REFSECT2"
|
><A
|
><A
|
NAME="AEN16179"
|
NAME="AEN16179"
|
></A
|
></A
|
><H3
|
><H3
|
><SPAN
|
><SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usb_endpoint_descriptor</SPAN
|
>usb_endpoint_descriptor</SPAN
|
></H3
|
></H3
|
><P
|
><P
|
>The host also needs information about which endpoint should be used
|
>The host also needs information about which endpoint should be used
|
for what. This involves an array of endpoint descriptors:</P
|
for what. This involves an array of endpoint descriptors:</P
|
><TABLE
|
><TABLE
|
BORDER="5"
|
BORDER="5"
|
BGCOLOR="#E0E0F0"
|
BGCOLOR="#E0E0F0"
|
WIDTH="70%"
|
WIDTH="70%"
|
><TR
|
><TR
|
><TD
|
><TD
|
><PRE
|
><PRE
|
CLASS="PROGRAMLISTING"
|
CLASS="PROGRAMLISTING"
|
>const usb_endpoint_descriptor usb_endpoints[] = {
|
>const usb_endpoint_descriptor usb_endpoints[] = {
|
{
|
{
|
length: USB_ENDPOINT_DESCRIPTOR_LENGTH,
|
length: USB_ENDPOINT_DESCRIPTOR_LENGTH,
|
type: USB_ENDPOINT_DESCRIPTOR_TYPE,
|
type: USB_ENDPOINT_DESCRIPTOR_TYPE,
|
endpoint: USB_ENDPOINT_DESCRIPTOR_ENDPOINT_OUT | 1,
|
endpoint: USB_ENDPOINT_DESCRIPTOR_ENDPOINT_OUT | 1,
|
attributes: USB_ENDPOINT_DESCRIPTOR_ATTR_BULK,
|
attributes: USB_ENDPOINT_DESCRIPTOR_ATTR_BULK,
|
max_packet_lo: 64,
|
max_packet_lo: 64,
|
max_packet_hi: 0,
|
max_packet_hi: 0,
|
interval: 0
|
interval: 0
|
},
|
},
|
{
|
{
|
length: USB_ENDPOINT_DESCRIPTOR_LENGTH,
|
length: USB_ENDPOINT_DESCRIPTOR_LENGTH,
|
type: USB_ENDPOINT_DESCRIPTOR_TYPE,
|
type: USB_ENDPOINT_DESCRIPTOR_TYPE,
|
endpoint: USB_ENDPOINT_DESCRIPTOR_ENDPOINT_IN | 2,
|
endpoint: USB_ENDPOINT_DESCRIPTOR_ENDPOINT_IN | 2,
|
attributes: USB_ENDPOINT_DESCRIPTOR_ATTR_BULK,
|
attributes: USB_ENDPOINT_DESCRIPTOR_ATTR_BULK,
|
max_packet_lo: 64,
|
max_packet_lo: 64,
|
max_packet_hi: 0,
|
max_packet_hi: 0,
|
interval: 0
|
interval: 0
|
}
|
}
|
};
|
};
|
|
|
const usbs_enumeration_data usb_enum_data = {
|
const usbs_enumeration_data usb_enum_data = {
|
…
|
…
|
total_number_endpoints: 2,
|
total_number_endpoints: 2,
|
endpoints: usb_endpoints,
|
endpoints: usb_endpoints,
|
…
|
…
|
};</PRE
|
};</PRE
|
></TD
|
></TD
|
></TR
|
></TR
|
></TABLE
|
></TABLE
|
><P
|
><P
|
>As usual the values for the <TT
|
>As usual the values for the <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>length</I
|
>length</I
|
></TT
|
></TT
|
> and
|
> and
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>type</I
|
>type</I
|
></TT
|
></TT
|
> fields are specified by the standard.
|
> fields are specified by the standard.
|
The <TT
|
The <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>endpoint</I
|
>endpoint</I
|
></TT
|
></TT
|
> field gives both the endpoint
|
> field gives both the endpoint
|
number and the direction, so in the above example endpoint 1 is used
|
number and the direction, so in the above example endpoint 1 is used
|
for OUT (host to peripheral) transfers and endpoint 2 is used for IN
|
for OUT (host to peripheral) transfers and endpoint 2 is used for IN
|
(peripheral to host) transfers. The
|
(peripheral to host) transfers. The
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>attributes</I
|
>attributes</I
|
></TT
|
></TT
|
> field indicates the USB protocol
|
> field indicates the USB protocol
|
that should be used on this endpoint: <TT
|
that should be used on this endpoint: <TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>CONTROL</TT
|
>CONTROL</TT
|
>,
|
>,
|
<TT
|
<TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>ISOCHRONOUS</TT
|
>ISOCHRONOUS</TT
|
>, <TT
|
>, <TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>BULK</TT
|
>BULK</TT
|
> or
|
> or
|
<TT
|
<TT
|
CLASS="LITERAL"
|
CLASS="LITERAL"
|
>INTERRUPT</TT
|
>INTERRUPT</TT
|
>. The
|
>. The
|
<TT
|
<TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>max_packet</I
|
>max_packet</I
|
></TT
|
></TT
|
> field specifies the maximum size
|
> field specifies the maximum size
|
of a single USB packet. For bulk transfers this will typically be 64
|
of a single USB packet. For bulk transfers this will typically be 64
|
bytes. For isochronous transfers this can be up to 1023 bytes. For
|
bytes. For isochronous transfers this can be up to 1023 bytes. For
|
interrupt transfers it can be up to 64 bytes, although usually a
|
interrupt transfers it can be up to 64 bytes, although usually a
|
smaller value will be used. The <TT
|
smaller value will be used. The <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>interval</I
|
>interval</I
|
></TT
|
></TT
|
>
|
>
|
field is ignored for control and bulk transfers. For isochronous
|
field is ignored for control and bulk transfers. For isochronous
|
transfers it should be set to 1. For interrupt transfers it can be a
|
transfers it should be set to 1. For interrupt transfers it can be a
|
value between 1 and 255, and indicates the number of milliseconds
|
value between 1 and 255, and indicates the number of milliseconds
|
between successive polling operations.</P
|
between successive polling operations.</P
|
><P
|
><P
|
>For USB peripherals involving multiple configurations or interfaces
|
>For USB peripherals involving multiple configurations or interfaces
|
the array of endpoint descriptors should be organized sequentially:
|
the array of endpoint descriptors should be organized sequentially:
|
first the endpoints corresponding to the first interface of the first
|
first the endpoints corresponding to the first interface of the first
|
configuration, then the second interface in that configuration, and so
|
configuration, then the second interface in that configuration, and so
|
on; then all the endpoints for all the interfaces in the second
|
on; then all the endpoints for all the interfaces in the second
|
configuration; etc.</P
|
configuration; etc.</P
|
></DIV
|
></DIV
|
><DIV
|
><DIV
|
CLASS="REFSECT2"
|
CLASS="REFSECT2"
|
><A
|
><A
|
NAME="AEN16196"
|
NAME="AEN16196"
|
></A
|
></A
|
><H3
|
><H3
|
>Strings</H3
|
>Strings</H3
|
><P
|
><P
|
>The enumeration data can contain a number of strings with additional
|
>The enumeration data can contain a number of strings with additional
|
information. Unicode encoding is used for the strings, and it is
|
information. Unicode encoding is used for the strings, and it is
|
possible for a peripheral to supply a given string in multiple
|
possible for a peripheral to supply a given string in multiple
|
languages using the appropriate characters. The first two bytes of
|
languages using the appropriate characters. The first two bytes of
|
each string give a length and type field. The first string is special;
|
each string give a length and type field. The first string is special;
|
after the two bytes header it consists of an array of 2-byte language
|
after the two bytes header it consists of an array of 2-byte language
|
id codes, indicating the supported languages. The language code
|
id codes, indicating the supported languages. The language code
|
0x0409 corresponds to English (United States). </P
|
0x0409 corresponds to English (United States). </P
|
><TABLE
|
><TABLE
|
BORDER="5"
|
BORDER="5"
|
BGCOLOR="#E0E0F0"
|
BGCOLOR="#E0E0F0"
|
WIDTH="70%"
|
WIDTH="70%"
|
><TR
|
><TR
|
><TD
|
><TD
|
><PRE
|
><PRE
|
CLASS="PROGRAMLISTING"
|
CLASS="PROGRAMLISTING"
|
>const unsigned char* usb_strings[] = {
|
>const unsigned char* usb_strings[] = {
|
"\004\003\011\004",
|
"\004\003\011\004",
|
"\020\003R\000e\000d\000 \000H\000a\000t\000"
|
"\020\003R\000e\000d\000 \000H\000a\000t\000"
|
};
|
};
|
|
|
const usbs_enumeration_data usb_enum_data = {
|
const usbs_enumeration_data usb_enum_data = {
|
…
|
…
|
total_number_strings: 2,
|
total_number_strings: 2,
|
strings: usb_strings,
|
strings: usb_strings,
|
…
|
…
|
};</PRE
|
};</PRE
|
></TD
|
></TD
|
></TR
|
></TR
|
></TABLE
|
></TABLE
|
><P
|
><P
|
>The default handler for standard control messages assumes that the
|
>The default handler for standard control messages assumes that the
|
peripheral only uses a single language. If this is not the case then
|
peripheral only uses a single language. If this is not the case then
|
higher-level code will have to handle the standard get-descriptor
|
higher-level code will have to handle the standard get-descriptor
|
control messages when a string descriptor is requested.</P
|
control messages when a string descriptor is requested.</P
|
></DIV
|
></DIV
|
><DIV
|
><DIV
|
CLASS="REFSECT2"
|
CLASS="REFSECT2"
|
><A
|
><A
|
NAME="AEN16201"
|
NAME="AEN16201"
|
></A
|
></A
|
><H3
|
><H3
|
><SPAN
|
><SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usbs_enumeration_data</SPAN
|
>usbs_enumeration_data</SPAN
|
></H3
|
></H3
|
><P
|
><P
|
>The <SPAN
|
>The <SPAN
|
CLASS="STRUCTNAME"
|
CLASS="STRUCTNAME"
|
>usbs_enumeration_data</SPAN
|
>usbs_enumeration_data</SPAN
|
> data structure
|
> data structure
|
collects together all the various descriptors that make up the
|
collects together all the various descriptors that make up the
|
enumeration data. It is the responsibility of application code to
|
enumeration data. It is the responsibility of application code to
|
supply a suitable data structure and install it in the control
|
supply a suitable data structure and install it in the control
|
endpoints's <TT
|
endpoints's <TT
|
CLASS="STRUCTFIELD"
|
CLASS="STRUCTFIELD"
|
><I
|
><I
|
>enumeration_data</I
|
>enumeration_data</I
|
></TT
|
></TT
|
> field before
|
> field before
|
the USB device is started.</P
|
the USB device is started.</P
|
></DIV
|
></DIV
|
></DIV
|
></DIV
|
><DIV
|
><DIV
|
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|
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ALIGN="left"
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HREF="usbs-intro.html"
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>Prev</A
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>Prev</A
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HREF="ecos-ref.html"
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|
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|
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WIDTH="33%"
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ALIGN="right"
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ALIGN="right"
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VALIGN="top"
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VALIGN="top"
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>Starting up a USB Device</TD
|
>Starting up a USB Device</TD
|
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