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<?xml-stylesheet type="text/xsl" href="https://community.arm.com/utility/feedstylesheets/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/"><channel><title>USB interrupts also when no cable is connected!</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/38617/usb-interrupts-also-when-no-cable-is-connected</link><description> 
Hello, 

 
I am not the world&amp;#39;s biggest USB expert, thus I am a little
puzzled about the LPC2478 needing to handle USB interrupts regularly
even when not connected to a host (without the USB cable connected,
even). I am running a CDC connection. Is</description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: USB interrupts also when no cable is connected!</title><link>https://community.arm.com/thread/90125?ContentTypeID=1</link><pubDate>Wed, 25 Nov 2009 10:15:32 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:8aeadb59-de06-4ed0-a7bd-c82ab4ef001e</guid><dc:creator>Tamir Michael</dc:creator><description>&lt;p&gt;&lt;p&gt;
Thanks, Tsuneo. Will do.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: USB interrupts also when no cable is connected!</title><link>https://community.arm.com/thread/57324?ContentTypeID=1</link><pubDate>Wed, 25 Nov 2009 10:03:58 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:55f3a8b1-3758-450e-8fe1-e6623e8fadc2</guid><dc:creator>Tsuneo Chinzei</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;&amp;gt; the LPC2478 needing to handle USB interrupts regularly
even when not connected to a host&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
Usually, you don&amp;#39;t see any USB interrupt while disconnection.&lt;br /&gt;
It may be caused by noise on the D+/D- pins.&lt;/p&gt;

&lt;p&gt;
For self-powered device,&lt;/p&gt;

&lt;p&gt;
- Disable USB engine while disconnection (PCUSB bit of PCONP).
Initialize it after the detection of VBUS voltage&lt;/p&gt;

&lt;p&gt;
OR&lt;/p&gt;

&lt;p&gt;
- Attach extra pull-ups (100k or more) to the D+ and D- pins, if
the USB engine is kept alive.&lt;/p&gt;

&lt;p&gt;
Tsuneo&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>