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RE: Adding a USB connecctor



Hi.
The 24 ohm resistors are probably used for termination of the signals.
We do not have them in our reference. The reason we do not have them is
because
it's working fine without them. The 1K5 pull-up should not be there. The
design
shows how to create an USB host connection. A 1K5 pull-up on the D+ line
indicates that
it's a high speed device (1K5 pull-up on the D- line indicates a low speed
device).
Connecting pin 1 on the USB connector directly to +5V is probably not
correct according to the
standard but this is also working fine for prototype purposes.

Regards
/Magnus


> -----Original Message-----
> From: Randall Allen Holman [mailto:holmanr@xxxxxxx.edu]
> Sent: den 29 maj 2002 18:40
> To: dev-etrax@xxxxxxx.com
> Subject: Adding a USB connecctor
> 
> 
> Hello,
> 
> I'm trying to add a USB connector to the Axis Dev Board LX.  I have
> already viewed the schematic drawing "How to add a USB device to your
> Developer Board LX card".  Before I actually hook this up, I 
> would like to
> ask a few questions.
> 
> When looking at the Philips Semiconductor website, I wanted 
> to look at the
> datasheet for the PDIUSBP11A USB XCVR.  They had general 
> hookup diagrams
> that "sort of" matched the one from Axis.
> 
> First of all, Philips  uses a 24 Ohm series resistor on both D+ and D-
> between the XCVR and the port.  There is also a 1.5K pullup 
> resistor on
> D+.  Why are these resistors missing on the dev-board 
> schematics??  Also,
> pin 1 of the USB connector is 5.0V Vcc. What is the Vbus signal on the
> Axis schematics?  Do I just connect this to the 5V power on my board??
> 
> Thanks,
> 
> Randy Holman
>