| 1 |
786 |
skrzyp |
<!-- Copyright (C) 2001 Free Software Foundation, Inc. -->
|
| 2 |
|
|
<!-- This material may be distributed only subject to the terms -->
|
| 3 |
|
|
<!-- and conditions set forth in the Open Publication License, v1.0 -->
|
| 4 |
|
|
<!-- or later (the latest version is presently available at -->
|
| 5 |
|
|
<!-- http://www.opencontent.org/openpub/). -->
|
| 6 |
|
|
<!-- Distribution of substantively modified versions of this -->
|
| 7 |
|
|
<!-- document is prohibited without the explicit permission of the -->
|
| 8 |
|
|
<!-- copyright holder. -->
|
| 9 |
|
|
<!-- Distribution of the work or derivative of the work in any -->
|
| 10 |
|
|
<!-- standard (paper) book form is prohibited unless prior -->
|
| 11 |
|
|
<!-- permission is obtained from the copyright holder. -->
|
| 12 |
|
|
<HTML
|
| 13 |
|
|
><HEAD
|
| 14 |
|
|
><TITLE
|
| 15 |
|
|
>Introduction</TITLE
|
| 16 |
|
|
><META
|
| 17 |
|
|
NAME="GENERATOR"
|
| 18 |
|
|
CONTENT="Modular DocBook HTML Stylesheet Version 1.64
|
| 19 |
|
|
"><LINK
|
| 20 |
|
|
REL="HOME"
|
| 21 |
|
|
TITLE="eCos Support for Developing USB-ethernet Peripherals"
|
| 22 |
|
|
HREF="io-usb-slave-eth.html"><LINK
|
| 23 |
|
|
REL="PREVIOUS"
|
| 24 |
|
|
TITLE="eCos Support for Developing USB-ethernet Peripherals"
|
| 25 |
|
|
HREF="io-usb-slave-eth.html"><LINK
|
| 26 |
|
|
REL="NEXT"
|
| 27 |
|
|
TITLE="Initializing the USB-ethernet Package"
|
| 28 |
|
|
HREF="usbseth-init.html"></HEAD
|
| 29 |
|
|
><BODY
|
| 30 |
|
|
CLASS="REFENTRY"
|
| 31 |
|
|
BGCOLOR="#FFFFFF"
|
| 32 |
|
|
TEXT="#000000"
|
| 33 |
|
|
LINK="#0000FF"
|
| 34 |
|
|
VLINK="#840084"
|
| 35 |
|
|
ALINK="#0000FF"
|
| 36 |
|
|
><DIV
|
| 37 |
|
|
CLASS="NAVHEADER"
|
| 38 |
|
|
><TABLE
|
| 39 |
|
|
WIDTH="100%"
|
| 40 |
|
|
BORDER="0"
|
| 41 |
|
|
CELLPADDING="0"
|
| 42 |
|
|
CELLSPACING="0"
|
| 43 |
|
|
><TR
|
| 44 |
|
|
><TH
|
| 45 |
|
|
COLSPAN="3"
|
| 46 |
|
|
ALIGN="center"
|
| 47 |
|
|
>eCos Support for Developing USB-ethernet Peripherals</TH
|
| 48 |
|
|
></TR
|
| 49 |
|
|
><TR
|
| 50 |
|
|
><TD
|
| 51 |
|
|
WIDTH="10%"
|
| 52 |
|
|
ALIGN="left"
|
| 53 |
|
|
VALIGN="bottom"
|
| 54 |
|
|
><A
|
| 55 |
|
|
HREF="io-usb-slave-eth.html"
|
| 56 |
|
|
>Prev</A
|
| 57 |
|
|
></TD
|
| 58 |
|
|
><TD
|
| 59 |
|
|
WIDTH="80%"
|
| 60 |
|
|
ALIGN="center"
|
| 61 |
|
|
VALIGN="bottom"
|
| 62 |
|
|
></TD
|
| 63 |
|
|
><TD
|
| 64 |
|
|
WIDTH="10%"
|
| 65 |
|
|
ALIGN="right"
|
| 66 |
|
|
VALIGN="bottom"
|
| 67 |
|
|
><A
|
| 68 |
|
|
HREF="usbseth-init.html"
|
| 69 |
|
|
>Next</A
|
| 70 |
|
|
></TD
|
| 71 |
|
|
></TR
|
| 72 |
|
|
></TABLE
|
| 73 |
|
|
><HR
|
| 74 |
|
|
ALIGN="LEFT"
|
| 75 |
|
|
WIDTH="100%"></DIV
|
| 76 |
|
|
><H1
|
| 77 |
|
|
><A
|
| 78 |
|
|
NAME="USBSETH-INTRO"
|
| 79 |
|
|
>Introduction</A
|
| 80 |
|
|
></H1
|
| 81 |
|
|
><DIV
|
| 82 |
|
|
CLASS="REFNAMEDIV"
|
| 83 |
|
|
><A
|
| 84 |
|
|
NAME="AEN6"
|
| 85 |
|
|
></A
|
| 86 |
|
|
><H2
|
| 87 |
|
|
>Name</H2
|
| 88 |
|
|
>Introduction -- eCos support for developing USB ethernet peripherals</DIV
|
| 89 |
|
|
><DIV
|
| 90 |
|
|
CLASS="REFSECT1"
|
| 91 |
|
|
><A
|
| 92 |
|
|
NAME="AEN9"
|
| 93 |
|
|
></A
|
| 94 |
|
|
><H2
|
| 95 |
|
|
>Introduction</H2
|
| 96 |
|
|
><P
|
| 97 |
|
|
>The eCos USB-ethernet package provides additional support for USB
|
| 98 |
|
|
peripherals that involve some sort of ethernet-style network. This can
|
| 99 |
|
|
be a traditional ethernet, or it can involve some other networking
|
| 100 |
|
|
technology that uses ethernet frames as a unit of transfer. It
|
| 101 |
|
|
provides functions to transfer ethernet frames over the USB bus,
|
| 102 |
|
|
handles certain control messages from the host, and optionally it can
|
| 103 |
|
|
provide a network device driver for use by the eCos TCP/IP stack.
|
| 104 |
|
|
The package comes with an example host-side device driver.</P
|
| 105 |
|
|
><P
|
| 106 |
|
|
>The USB-ethernet package is not tied to any specific hardware. It
|
| 107 |
|
|
requires the presence of USB hardware and a suitable device driver,
|
| 108 |
|
|
but not all USB peripherals involve ethernet communications. Hence the
|
| 109 |
|
|
configuration system cannot load the package automatically for
|
| 110 |
|
|
specific targets, in the way that a USB device driver or an ethernet
|
| 111 |
|
|
driver can be loaded automatically. Instead, the package has to be
|
| 112 |
|
|
added explicitly. When using the command line tools this will involve
|
| 113 |
|
|
an operation like the following:</P
|
| 114 |
|
|
><TABLE
|
| 115 |
|
|
BORDER="0"
|
| 116 |
|
|
BGCOLOR="#E0E0E0"
|
| 117 |
|
|
WIDTH="100%"
|
| 118 |
|
|
><TR
|
| 119 |
|
|
><TD
|
| 120 |
|
|
><PRE
|
| 121 |
|
|
CLASS="SCREEN"
|
| 122 |
|
|
>$ ecosconfig add usbs_eth</PRE
|
| 123 |
|
|
></TD
|
| 124 |
|
|
></TR
|
| 125 |
|
|
></TABLE
|
| 126 |
|
|
><P
|
| 127 |
|
|
>Typically, this will automatically cause the USB device driver to
|
| 128 |
|
|
become active. Loading the USB-ethernet package automatically provides
|
| 129 |
|
|
functionality for <A
|
| 130 |
|
|
HREF="usbseth-init.html"
|
| 131 |
|
|
>initialization</A
|
| 132 |
|
|
>,
|
| 133 |
|
|
<A
|
| 134 |
|
|
HREF="usbseth-data.html"
|
| 135 |
|
|
>data transfer</A
|
| 136 |
|
|
>, and the handling of
|
| 137 |
|
|
<A
|
| 138 |
|
|
HREF="usbseth-control.html"
|
| 139 |
|
|
>control messages</A
|
| 140 |
|
|
> and state
|
| 141 |
|
|
changes. If the current configuration includes the eCos TCP/IP stack
|
| 142 |
|
|
then the <A
|
| 143 |
|
|
HREF="usbseth-netdev.html"
|
| 144 |
|
|
>network device driver</A
|
| 145 |
|
|
>
|
| 146 |
|
|
support will be enabled as well by default, allowing the stack to
|
| 147 |
|
|
exchange ethernet frames over the USB bus.</P
|
| 148 |
|
|
><P
|
| 149 |
|
|
>There is a USB standard for a class of communication devices including
|
| 150 |
|
|
ethernet. The package does not implement this standard, due to
|
| 151 |
|
|
limitations in the hardware for which the package was first developed.
|
| 152 |
|
|
Instead, the package uses its own <A
|
| 153 |
|
|
HREF="usbseth-protocol.html"
|
| 154 |
|
|
>protocol</A
|
| 155 |
|
|
> between USB
|
| 156 |
|
|
<A
|
| 157 |
|
|
HREF="usbseth-host.html"
|
| 158 |
|
|
>host device driver</A
|
| 159 |
|
|
> and the
|
| 160 |
|
|
peripheral. </P
|
| 161 |
|
|
></DIV
|
| 162 |
|
|
><DIV
|
| 163 |
|
|
CLASS="REFSECT1"
|
| 164 |
|
|
><A
|
| 165 |
|
|
NAME="AEN22"
|
| 166 |
|
|
></A
|
| 167 |
|
|
><H2
|
| 168 |
|
|
>Usage Scenarios</H2
|
| 169 |
|
|
><P
|
| 170 |
|
|
>The USB-ethernet package can be used several different scenarios. In
|
| 171 |
|
|
a simple scenario, the peripheral serves only to connect the USB host
|
| 172 |
|
|
to a suitable network:</P
|
| 173 |
|
|
><DIV
|
| 174 |
|
|
CLASS="INFORMALFIGURE"
|
| 175 |
|
|
><A
|
| 176 |
|
|
NAME="AEN25"
|
| 177 |
|
|
></A
|
| 178 |
|
|
><P
|
| 179 |
|
|
></P
|
| 180 |
|
|
><DIV
|
| 181 |
|
|
CLASS="MEDIAOBJECT"
|
| 182 |
|
|
><P
|
| 183 |
|
|
><IMG
|
| 184 |
|
|
SRC="simple.gif"
|
| 185 |
|
|
></IMG
|
| 186 |
|
|
></P
|
| 187 |
|
|
></DIV
|
| 188 |
|
|
><P
|
| 189 |
|
|
></P
|
| 190 |
|
|
></DIV
|
| 191 |
|
|
><P
|
| 192 |
|
|
>After initialization, and once the USB connection between host and
|
| 193 |
|
|
peripheral has been established, higher-level code needs to detect
|
| 194 |
|
|
packets that are intended for the host, and to forward these. This can
|
| 195 |
|
|
be achieved by the low-level <TT
|
| 196 |
|
|
CLASS="FUNCTION"
|
| 197 |
|
|
>usbs_eth_start_tx</TT
|
| 198 |
|
|
>
|
| 199 |
|
|
function. Similarly, higher-level code needs to detect packets coming
|
| 200 |
|
|
from the host, using <TT
|
| 201 |
|
|
CLASS="FUNCTION"
|
| 202 |
|
|
>usbs_eth_start_rx</TT
|
| 203 |
|
|
>, and to
|
| 204 |
|
|
forward these using the real network. As far as the host is concerned
|
| 205 |
|
|
it is connected directly to the network. In this scenario there is no
|
| 206 |
|
|
confusion about addresses: there is a single MAC address for the
|
| 207 |
|
|
host/peripheral combination, corresponding to the connection to the
|
| 208 |
|
|
real network, and it is this address which should be supplied during
|
| 209 |
|
|
<A
|
| 210 |
|
|
HREF="usbseth-init.html"
|
| 211 |
|
|
>initialization</A
|
| 212 |
|
|
>.</P
|
| 213 |
|
|
><P
|
| 214 |
|
|
>In a more complicated scenario, there is a TCP/IP stack running inside
|
| 215 |
|
|
the peripheral.</P
|
| 216 |
|
|
><DIV
|
| 217 |
|
|
CLASS="INFORMALFIGURE"
|
| 218 |
|
|
><A
|
| 219 |
|
|
NAME="AEN36"
|
| 220 |
|
|
></A
|
| 221 |
|
|
><P
|
| 222 |
|
|
></P
|
| 223 |
|
|
><DIV
|
| 224 |
|
|
CLASS="MEDIAOBJECT"
|
| 225 |
|
|
><P
|
| 226 |
|
|
><IMG
|
| 227 |
|
|
SRC="tcpip.gif"
|
| 228 |
|
|
></IMG
|
| 229 |
|
|
></P
|
| 230 |
|
|
></DIV
|
| 231 |
|
|
><P
|
| 232 |
|
|
></P
|
| 233 |
|
|
></DIV
|
| 234 |
|
|
><P
|
| 235 |
|
|
>This involves the USB-ethernet package providing a service both to the
|
| 236 |
|
|
host and to the eCos TCP/IP stack. It achieves the latter by acting as
|
| 237 |
|
|
an eCos network device. Typically, the TCP/IP stack will be configured
|
| 238 |
|
|
to act as a network bridge. The USB peripheral needs to examine the
|
| 239 |
|
|
packets arriving over the real network. Some of these packets will be
|
| 240 |
|
|
intended for the host, while others will be intended for the
|
| 241 |
|
|
peripheral itself. To distinguish between these two scenarios, two
|
| 242 |
|
|
distinct MAC addresses are needed: one for the host, and one for the
|
| 243 |
|
|
peripheral. Similarly, packets sent by the host may have to be
|
| 244 |
|
|
forwarded via the real network, or they may be intended for the TCP/IP
|
| 245 |
|
|
stack inside the peripheral. Packets generated inside the peripheral's
|
| 246 |
|
|
TCP/IP stack may need to be sent via the real network or over the USB
|
| 247 |
|
|
bus. The network bridge software will have to take care of all these
|
| 248 |
|
|
possibilities. Unusually for a network bridge, one of the network
|
| 249 |
|
|
segments being bridged will only ever have one machine attached.</P
|
| 250 |
|
|
><P
|
| 251 |
|
|
>There are other possible usage scenarios. For example, the peripheral
|
| 252 |
|
|
might not be attached to a real network at all. Instead it could be
|
| 253 |
|
|
the USB host that acts as a network bridge, allowing a TCP/IP stack
|
| 254 |
|
|
inside the peripheral to communicate with the outside world. The
|
| 255 |
|
|
various details will depend on the exact type of peripheral being
|
| 256 |
|
|
developed. </P
|
| 257 |
|
|
></DIV
|
| 258 |
|
|
><DIV
|
| 259 |
|
|
CLASS="NAVFOOTER"
|
| 260 |
|
|
><HR
|
| 261 |
|
|
ALIGN="LEFT"
|
| 262 |
|
|
WIDTH="100%"><TABLE
|
| 263 |
|
|
WIDTH="100%"
|
| 264 |
|
|
BORDER="0"
|
| 265 |
|
|
CELLPADDING="0"
|
| 266 |
|
|
CELLSPACING="0"
|
| 267 |
|
|
><TR
|
| 268 |
|
|
><TD
|
| 269 |
|
|
WIDTH="33%"
|
| 270 |
|
|
ALIGN="left"
|
| 271 |
|
|
VALIGN="top"
|
| 272 |
|
|
><A
|
| 273 |
|
|
HREF="io-usb-slave-eth.html"
|
| 274 |
|
|
>Prev</A
|
| 275 |
|
|
></TD
|
| 276 |
|
|
><TD
|
| 277 |
|
|
WIDTH="34%"
|
| 278 |
|
|
ALIGN="center"
|
| 279 |
|
|
VALIGN="top"
|
| 280 |
|
|
><A
|
| 281 |
|
|
HREF="io-usb-slave-eth.html"
|
| 282 |
|
|
>Home</A
|
| 283 |
|
|
></TD
|
| 284 |
|
|
><TD
|
| 285 |
|
|
WIDTH="33%"
|
| 286 |
|
|
ALIGN="right"
|
| 287 |
|
|
VALIGN="top"
|
| 288 |
|
|
><A
|
| 289 |
|
|
HREF="usbseth-init.html"
|
| 290 |
|
|
>Next</A
|
| 291 |
|
|
></TD
|
| 292 |
|
|
></TR
|
| 293 |
|
|
><TR
|
| 294 |
|
|
><TD
|
| 295 |
|
|
WIDTH="33%"
|
| 296 |
|
|
ALIGN="left"
|
| 297 |
|
|
VALIGN="top"
|
| 298 |
|
|
>eCos Support for Developing USB-ethernet Peripherals</TD
|
| 299 |
|
|
><TD
|
| 300 |
|
|
WIDTH="34%"
|
| 301 |
|
|
ALIGN="center"
|
| 302 |
|
|
VALIGN="top"
|
| 303 |
|
|
> </TD
|
| 304 |
|
|
><TD
|
| 305 |
|
|
WIDTH="33%"
|
| 306 |
|
|
ALIGN="right"
|
| 307 |
|
|
VALIGN="top"
|
| 308 |
|
|
>Initializing the USB-ethernet Package</TD
|
| 309 |
|
|
></TR
|
| 310 |
|
|
></TABLE
|
| 311 |
|
|
></DIV
|
| 312 |
|
|
></BODY
|
| 313 |
|
|
></HTML
|
| 314 |
|
|
>
|
