+++ /dev/null
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->Introduction</TITLE
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-TITLE="eCos Support for Developing USB-ethernet Peripherals"
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-><H1
-><A
-NAME="USBSETH-INTRO">Introduction</H1
-><DIV
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->Name</H2
->Introduction -- eCos support for developing USB ethernet peripherals</DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN17364"
-></A
-><H2
->Introduction</H2
-><P
->The eCos USB-ethernet package provides additional support for USB
-peripherals that involve some sort of ethernet-style network. This can
-be a traditional ethernet, or it can involve some other networking
-technology that uses ethernet frames as a unit of transfer. It
-provides functions to transfer ethernet frames over the USB bus,
-handles certain control messages from the host, and optionally it can
-provide a network device driver for use by the eCos TCP/IP stack.
-The package comes with an example host-side device driver.</P
-><P
->The USB-ethernet package is not tied to any specific hardware. It
-requires the presence of USB hardware and a suitable device driver,
-but not all USB peripherals involve ethernet communications. Hence the
-configuration system cannot load the package automatically for
-specific targets, in the way that a USB device driver or an ethernet
-driver can be loaded automatically. Instead, the package has to be
-added explicitly. When using the command line tools this will involve
-an operation like the following:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="SCREEN"
->$ ecosconfig add usbs_eth</PRE
-></TD
-></TR
-></TABLE
-><P
->Typically, this will automatically cause the USB device driver to
-become active. Loading the USB-ethernet package automatically provides
-functionality for <A
-HREF="usbseth-init.html"
->initialization</A
->,
-<A
-HREF="usbseth-data.html"
->data transfer</A
->, and the handling of
-<A
-HREF="usbseth-control.html"
->control messages</A
-> and state
-changes. If the current configuration includes the eCos TCP/IP stack
-then the <A
-HREF="usbseth-netdev.html"
->network device driver</A
->
-support will be enabled as well by default, allowing the stack to
-exchange ethernet frames over the USB bus.</P
-><P
->There is a USB standard for a class of communication devices including
-ethernet. The package does not implement this standard, due to
-limitations in the hardware for which the package was first developed.
-Instead, the package uses its own <A
-HREF="usbseth-protocol.html"
->protocol</A
-> between USB
-<A
-HREF="usbseth-host.html"
->host device driver</A
-> and the
-peripheral. </P
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN17377"
-></A
-><H2
->Usage Scenarios</H2
-><P
->The USB-ethernet package can be used several different scenarios. In
-a simple scenario, the peripheral serves only to connect the USB host
-to a suitable network:</P
-><DIV
-CLASS="INFORMALFIGURE"
-><A
-NAME="AEN17380"><P
-></P
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-CLASS="MEDIAOBJECT"
-><P
-><IMG
-SRC="simple.png"
-ALIGN="CENTER"></P
-></DIV
-><P
-></P
-></DIV
-><P
->After initialization, and once the USB connection between host and
-peripheral has been established, higher-level code needs to detect
-packets that are intended for the host, and to forward these. This can
-be achieved by the low-level <TT
-CLASS="FUNCTION"
->usbs_eth_start_tx</TT
->
-function. Similarly, higher-level code needs to detect packets coming
-from the host, using <TT
-CLASS="FUNCTION"
->usbs_eth_start_rx</TT
->, and to
-forward these using the real network. As far as the host is concerned
-it is connected directly to the network. In this scenario there is no
-confusion about addresses: there is a single MAC address for the
-host/peripheral combination, corresponding to the connection to the
-real network, and it is this address which should be supplied during
-<A
-HREF="usbseth-init.html"
->initialization</A
->.</P
-><P
->In a more complicated scenario, there is a TCP/IP stack running inside
-the peripheral.</P
-><DIV
-CLASS="INFORMALFIGURE"
-><A
-NAME="AEN17389"><P
-></P
-><DIV
-CLASS="MEDIAOBJECT"
-><P
-><IMG
-SRC="tcpip.png"
-ALIGN="CENTER"></P
-></DIV
-><P
-></P
-></DIV
-><P
->This involves the USB-ethernet package providing a service both to the
-host and to the eCos TCP/IP stack. It achieves the latter by acting as
-an eCos network device. Typically, the TCP/IP stack will be configured
-to act as a network bridge. The USB peripheral needs to examine the
-packets arriving over the real network. Some of these packets will be
-intended for the host, while others will be intended for the
-peripheral itself. To distinguish between these two scenarios, two
-distinct MAC addresses are needed: one for the host, and one for the
-peripheral. Similarly, packets sent by the host may have to be
-forwarded via the real network, or they may be intended for the TCP/IP
-stack inside the peripheral. Packets generated inside the peripheral's
-TCP/IP stack may need to be sent via the real network or over the USB
-bus. The network bridge software will have to take care of all these
-possibilities. Unusually for a network bridge, one of the network
-segments being bridged will only ever have one machine attached.</P
-><P
->There are other possible usage scenarios. For example, the peripheral
-might not be attached to a real network at all. Instead it could be
-the USB host that acts as a network bridge, allowing a TCP/IP stack
-inside the peripheral to communicate with the outside world. The
-various details will depend on the exact type of peripheral being
-developed. </P
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