URL
https://opencores.org/ocsvn/openrisc/openrisc/trunk
Subversion Repositories openrisc
[/] [openrisc/] [trunk/] [rtos/] [ecos-2.0/] [doc/] [html/] [ref/] [usbs-start.html] - Rev 201
Go to most recent revision | Compare with Previous | Blame | View Log
<!-- Copyright (C) 2003 Red Hat, Inc. -->
<!-- This material may be distributed only subject to the terms -->
<!-- and conditions set forth in the Open Publication License, v1.0 -->
<!-- or later (the latest version is presently available at -->
<!-- http://www.opencontent.org/openpub/). -->
<!-- Distribution of the work or derivative of the work in any -->
<!-- standard (paper) book form is prohibited unless prior -->
<!-- permission is obtained from the copyright holder. -->
<HTML
><HEAD
><TITLE
>Starting up a USB Device</TITLE
><meta name="MSSmartTagsPreventParsing" content="TRUE">
<META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
"><LINK
REL="HOME"
TITLE="eCos Reference Manual"
HREF="ecos-ref.html"><LINK
REL="UP"
TITLE="eCos USB Slave Support"
HREF="io-usb-slave.html"><LINK
REL="PREVIOUS"
TITLE="USB Enumeration Data"
HREF="usbs-enum.html"><LINK
REL="NEXT"
TITLE="Devtab Entries"
HREF="usbs-devtab.html"></HEAD
><BODY
CLASS="REFENTRY"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>eCos Reference Manual</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="usbs-enum.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="usbs-devtab.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><H1
><A
NAME="USBS-START">Starting up a USB Device</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN16210"
></A
><H2
>Name</H2
><TT
CLASS="FUNCTION"
>usbs_start</TT
> -- Starting up a USB Device</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN16214"><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN16215"><P
></P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include <cyg/io/usb/usbs.h></PRE
></TD
></TR
></TABLE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>void usbs_start</CODE
>(usbs_control_endpoint* ep0);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN16222"
></A
><H2
>Description</H2
><P
>Initializing a USB device requires some support from higher-level
code, typically the application, in the form of enumeration data.
Hence it is not possible for the low-level USB driver to activate a
USB device itself. Instead the higher-level code has to take care of
this by invoking <TT
CLASS="FUNCTION"
>usbs_start</TT
>. This function takes
a pointer to a USB control endpoint data structure. USB device drivers
should provide exactly one such data structure for every USB device,
so the pointer uniquely identifies the device.</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>const usbs_enumeration_data usb_enum_data = {
…
};
int
main(int argc, char** argv)
{
usbs_sa11x0_ep0.enumeration_data = &usb_enum_data;
…
usbs_start(&usbs_sa11x0_ep0);
…
}</PRE
></TD
></TR
></TABLE
><P
>The exact behaviour of <TT
CLASS="FUNCTION"
>usbs_start</TT
> depends on the
USB hardware and the device driver. A typical implementation would
change the USB data pins from tristated to active. If the peripheral
is already plugged into a host then the latter should detect this
change and start interacting with the peripheral, including requesting
the enumeration data. Some of this may happen before
<TT
CLASS="FUNCTION"
>usbs_start</TT
> returns, but given that multiple
interactions between USB host and peripheral are required it is likely
that the function will return before the peripheral is fully
configured. Control endpoints provide a <A
HREF="usbs-control.html#AEN16552"
>mechanism</A
> for informing
higher-level code of USB state changes.
<TT
CLASS="FUNCTION"
>usbs_start</TT
> will return even if the peripheral is
not currently connected to a host: it will not block until the
connection is established.</P
><P
><TT
CLASS="FUNCTION"
>usbs_start</TT
> should only be called once for a given
USB device. There are no defined error conditions. Note that the
function affects the entire USB device and not just the control
endpoint: there is no need to start any data endpoints as well.</P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="usbs-enum.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="ecos-ref.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="usbs-devtab.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>USB Enumeration Data</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="io-usb-slave.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Devtab Entries</TD
></TR
></TABLE
></DIV
></BODY
></HTML
> Go to most recent revision | Compare with Previous | Blame | View Log